AAS News RSS

MAVEN clouds cover

Editor’s Note: This week we’re at the joint 48th meeting of the Division for Planetary Sciences (DPS) and 11th European Planetary Science Congress (EPSC) in Pasadena, California. Along with astrobites author Natasha Batalha, I will be writing updates on selected events at the meeting and posting at the end of each day. Follow along here or at astrobites.com! The usual posting schedule for AAS Nova will resume next week.

Come visit us at our poster with AAS Nova! #419.02

Come visit us at our poster with AAS Nova! #419.02

This week Astrobites will be reporting from the joint 48th meeting of the Division for Planetary Sciences (DPS) and 11th European Planetary Science Congress (EPSC) in Pasadena, California! Two astrobiters are attending this conference, and we will report highlights from each day here on astrobites. If you’d like to see more timely updates during the day, we encourage you to search the #DPSEPSC hashtag!

Monday morning was the official start of the meeting. We’ve got a joint poster for Astrobites/AAS Nova at poster #419.02 in the exhibit hall — come stop by to chat (and for stickers!). For those of you who can’t be here in person, here’s an update on the plenaries and press conferences from the first day of DPS this year.

Jonathan Eberhart Planetary Sciences Journalism Award (by Natasha Batalha)

The meeting kicked off with the presentation of the Jonathan Eberhart Planetary Sciences Journalism Award, which was awarded to Nadia Drake. Nadia has been an instrumental figure in space sciences communication. She’s reported on everything from other worlds to exploding stars, to the fabric of the universe. Her work is an inspiration to many of us here at Astrobites. Be sure to check out her stuff!

Artist’s impression of Rosetta, Philae, and Comet 67P. [ESA/ATG medialab; ESA/Rosetta/NavCam]

Artist’s impression of Rosetta, Philae, and Comet 67P. [ESA/ATG medialab; ESA/Rosetta/NavCam]

Plenaries (by Natasha Batalha)

The Rosetta Mission: Matt Taylor

The Rosetta Mission gathered huge media attention in November 2014 when its robotic lander, Philae, landed on comet 67P/Churyumov-Gerasimenko. Almost two years later, Matt Taylor stands on the stage of Ballroom D to report on the mission’s current status. Rosetta was given its name because, like the Rosetta stone, the spacecraft is a key to deciphering the origin of the Solar System. Dr. Taylor begins by showing just a small fraction of the copious amounts of images that were gathered. Comets, which were previously thought of as icy dust balls, are now known to be geologically complex places, he discusses. Rosetta has paved a completely new field of cometary geology and they’ve still only analyzed about 5% of all the data that was collected.

“Now that we have the whole data set we are revising our numbers to get a sense of the whole picture.” 

From measurements of the molecular oxygen, combined with the detection of nitrogen, noble gases and the D/H ratio in the water, we know that this comet was born in a very cold region in the protoplanetary nebula, far from the Sun. Meaning, this comet might offer us a glimpse of what the building blocks of planets and moons may have been. The D/H ratio also tells us that Earth’s water was likely not delivered from comets, since the D/H values from the comet do not match those from Earth’s oceans. But from looking at the data taken from Noble gasses, it’s possible that other complex material may have been.

In late September of this year, the Rosetta mission concluded its mission as planned with a controlled impact onto the comet. On decent they were able to successfully study the comet’s gas, dust and plasma very close to the surface.

“We’ve got the Rosetta stone, now we have decades or work to do to analyze the data.”

The Latest Views of Venus as Observed by the Japanese Orbiter: Takehiko Satoh

Artist’s illustration of the “Akatsuki” mission to Venus. [JAXA]

Artist’s illustration of the “Akatsuki” mission to Venus. [JAXA]

Just one year ago, the Japanese Aerospace Exploration Agency held a press conference to announce the successful arrival of Akatsuki, Japan’s very first planetary orbiter, into a Venus orbit. Dr. Takehiko Satoh is here to today give an overview of the mission. Understanding the atmosphere of Venus has been difficult because of the thick cloud decks that inhibit our ability to see down to the surface.

Dr. Satoh explained that Akatsuki’s mission is to understand and detail the atmospheric dynamics of Venus, get a 3-D view of wind fields and describe any spatial and temporal variations in the atmosphere. This includes answering the long standing question of whether or not Venus has lightning and/or volcanism. Akatsuki is also the first and only meteorological satellite orbiting a planet other than the Earth, which will lead to some very interesting data in the near future.

Unfortunately we will have to wait a while to answer all of those questions considering first light images were taken in December of 2015 and regular observations started on April 1, 2016. Nevertheless, Dr. Satoh was able to show some very exciting preliminary studies:

  1. They visualized the cloud motion and variations of minor gases on Venus by acquiring multi-wavelength images continuously through time.
  2. They looked at fine scale features in order to attempt to detect lightning in the night (none have been detected so far).
  3. They detected SO2 absorption and also detected an unknown absorber at 365 nm! Dr. Satoh poses the questions, what is actually there? And how are they related to atmospheric dynamics and cloud formation?
  4. They mapped thermal emission from the surface and detected an E-W elongated low temperature region.

Dr. Satoh ended by explaining that their team has a lot of work to do in order to fully synthesize all of these discoveries but that in the near future we should expect a lot more interesting science!!

New Horizons

Illustration of the New Horizons spacecraft’s encounter with the Pluto–Charon system. [NASA/JHU APL/SwRI/Steve Gribben]

New Horizons: Overview of Results From and Plans After the Exploration of the Pluto System: S.A. Stern

The last plenary talk was given by Dr. Alan Stern who gave an exciting overview of the New Horizons mission. He started by showing the massive scientific payload that allowed New Horizons to accomplish, what he says is as much science as several Mars missions, combined.  In fact, the mission met all of its science objectives, published over 40 studies and presented findings at over 200 meetings. New Horizons also just recently won and initiated its extend mission, which warrants a massive congratulations to the New Horizon’s team! So what were the major scientific studies you should be on the lookout for?

Dr. Stern says the most surprising finding (for him) was the stark difference between Pluto and Charon. Pluto and Charon have similar densities and sizes and New Horizons also showed that there was, at some point, some degree of atmospheric transfer from Pluto to Charon. Besides that though, everything else (surface & atmosphere) about the two bodies are wildly different. Pluto has a complex and active surface. Some terrains on Pluto are brand new, while others formed over four billion years ago. Pluto also has a complex atmosphere, which contains molecules such as water, methane and nitrogen. They also found that these molecules are not uniformly distributed around the planet. Charon, on the other hand, has no detectable atmosphere — or, if it does, it is smaller than the atmosphere of our very own Moon. Charon’s terrains are also all older than four billion years old, with no new activity.

Dr. Stern says they is still a lot of work to be done to answer exactly how these planets ended up with such different properties. And THIS Sunday all the New Horizons data will be available, so you too can download it and start to analyze some of these peculiar features.

First Press Conference (by Susanna Kohler)

Idunn Mons

An elevation model of Venus’s volcano Idunn Mons. [ESA/DLR]

The first press conference of the meeting opened with a talk by Piero D’Incecco (German Aerospace Center), who discussed evidence for recently active lava flows on Venus. Using clever numerical modeling techniques combined with observations from ESA’s Venus Express mission, D’Incecco and collaborators have looked through Venus’s thick cloud cover in infrared wavelengths to detect several lava flows from the top and eastern flank of the volcano Idunn Mons, which is located in Venus’s southern hemisphere. The team’s work has focused on identifying the location and extent of these flows to learn more about volcanism on the surface of Earth’s “twin” planet. The full press release can be found here.

Next up was Nick Schneider (Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder), who spoke about the most recent results from the MAVEN mission to Mars. Three interesting findings have come from MAVEN’s unprecedented ultraviolet coverage of Mars:

  1. Observations of “nightglow” emission on Mars’s night side, as its atmosphere emits light in UV due to chemical reactions that start on its day side. These observations reveal information about Mar’s high-altitude winds.
  2. Evidence that ozone in Mars’s atmosphere accumulates inside a vortex at Mars’s pole during the winter time — again, providing critical information about the global circulation about Mars’s atmosphere.
  3. Beautiful observations of afternoon cloud formation over Mars’s four giant volcanos, suggesting cloud formation happens there in a similar way to cloud formation over Earth’s mountain ranges.

The full press release can be found here.

MAVEN clouds

Images from MAVEN’s Imaging UltraViolet Spectrograph demonstrating the rapid cloud formation in Mar’s atmosphere. These images were taken over the span of ~7 hours. [NASA/MAVEN/University of Colorado]

Next came a series of three talks on the intriguing comet 67P/Churyumov-Gerasimenko. The first was by Mattia Galiazzo (Western University, Canada), on a study of the origin of comet 67P. Using computer simulations, Galiazzo and collaborators modeled the comet’s most probable orbit in order to discover where the body came from. They find that 67P is likely relatively new to the inner parts of our solar system, having lived in the scattered disk — the outskirts of the solar system — for millions of years. Perturbations by other bodies in our solar system then tweaked the comet’s orbit until it arrived in the inner region only ~10,000 years ago. The full press release can be found here.

67P outburst

A collimated outburst from Comet 67P, as captured by Rosetta’s OSIRIS camera. [ESA/Rosetta/OSIRIS]

Stubbe Hvidd (German Aerospace Center) next gave a dynamic talk on 67P as the “creaking and cracking comet”. Hvidd used high-resolution imaging of the comet to demonstrate that its surface has several recently-formed cracks — especially in its neck, the narrow region between its two lobes — that indicate it’s under stress as it hurtles through space in its orbit. Hvidd and collaborators have modeled the forces on the comet to show that its rotation and activity are creating stresses that will likely change the shape of the comet over the next several hundred years.

Finally, Jordan Steckloff (Planetary Science Institute) wrapped things up with a discussion of outbursts from comets like 67P. Steckloff suggests that, rather than being caused by internal pressure like geysers on Earth, comet outbursts might the result of avalanches on their surfaces. He showed that material sliding down the comet’s surface to a local low-potential point can enter a region that is sublimating due to sunlight exposure. As the granular materials slide into this region, they can be blown off in a tightly collimated plume that matches observations of comet outbursts. The full press release can be found here.

Europa

Next week we’ll be reporting from the joint 48th meeting of the Division for Planetary Sciences (DPS) and 11th European Planetary Science Congress (EPSC). Planetary science articles are a large component of the work featured in AAS journals; nearly 400 planetary science articles were published in AAS journals in 2015 alone, and these have already gathered almost 2400 citations.

In the lead-up to next week’s meeting, we’d like to introduce Melissa McGrath, our new Lead Editor for the Solar System, Exoplanets, and Astrobiology corridor. Melissa is a Senior Scientist at the SETI Institute. Her impressive list of former positions includes Deputy Director of NASA’s Science Mission Directorate’s Planetary Science Division, and Chair of the AAS’s Division for Planetary Sciences.

* * * * *

JUICE

Artist’s impression of the planned Jupiter Icy moons Explorer (JUICE) mission that will study Ganymede, Callisto, and Europa. [NASA/JPL]

Tell me about your field of research and some of your current projects.

I’ve worked on a wide variety of things, primarily planet and satellites atmospheres, particularly the Galilean satellites of Jupiter. I’m currently involved in several Hubble Space Telescope observing programs, and I’m also a co-investigator on three instruments flying on missions to Europa and Ganymede.

What is your history with the AAS Journals?

I started out as a Scientific Editor for AJ in 2009 handling the solar system papers. I then was added to both ApJ Letters and ApJ as a Scientific Editor. Now I am one of the six Lead Editors for AAS Journals (ApJ + AJ), handling solar system, exoplanets, and astrobiology papers.

What do you anticipate will be some of the most exciting topics presented on at the DPS/EPSC meeting next week?

Planet Nine, results from the New Horizons mission to Pluto, the first results from the Juno mission, and the latest work on exoplanets, to name just a few!

What do you consider to be some of the biggest open questions in the field of planetary science today?

Is there life beyond Earth in the solar system? How did our own solar system form?

exoplanet atmosphere

Artist’s impression of the atmosphere of a rocky exoplanet. [NASA/Dana Berry (SkyWorks)]

Your journal corridor, “Solar System, Exoplanets, and Astrobiology”, encompasses a broad range of topics. How do you feel that these different areas of research all fit together?

They are tied closely together by the search for life beyond Earth, by understanding how planetary systems form and evolve. They are also tied closely together by the study of planetary atmospheres, both within our own solar system and in exoplanets.

What do you think makes for a well-authored paper?

The most fundamental thing is having a new result and explaining it in a clear, concise, and convincing fashion.

Is there anything else you’d like to share about the publishing process with potential authors?

I’m continually impressed with how professional the whole process of peer review and publishing of new science results is. Both the authors and referees do an outstanding job, and almost without exception they are both geared to making high-quality science research available to the community in a positive, success-oriented process. That makes being an Editor a fun job for the most part.

* * * * *

Look for the AAS Publishing team at DPS 48/EPSC 11 next week — we’ll be in the exhibit hall at Booth #101! And if you can’t be at the meeting, be sure to check back on this site all next week, as AAS Nova and Astrobites will be working together to bring you daily updates from the meeting.

illustration of a spacecraft in front of the milky way, with multiple patches identified along a sinusoidal curve.

Editor’s Note: Last week we were at the 228th AAS Meeting in San Diego, CA. Here is a final post about selected events on the last day of the meeting, written by authors from astrobites.com, a grad-student collaborative project with which we recently announced a new partnership! Starting in July, keep an eye out for astrobites posts at AAS Nova in between Highlights (i.e., on Tuesdays and Thursdays). We’re excited to be working together to bring you more recent astronomy research from AAS journals!

Extrasolar Planets: Detection (by Leonardo dos Santos)

Thursday’s first session on exoplanets was about detecting these distant worlds, and the opening talk was given by Robert Siverd (Las Cumbres Observatory). He describes the NRES, a network of spectrographs that will look for exoplanets using the radial velocity method. One of the coolest aspects of this instrument is that it will feature an “on the fly” scheduling system that will perform observations as efficiently as possible. The spectrograph is still being tested, but a unit will be deployed at CTIO later this year.

Measuring the depths of transits and eclipses in Spitzer has been problematic in the past, since the Spitzer instrument IRAC (InfraRed Array Camera) has a non-uniform response in its detector’s pixels. But, as reported by James Ingalls (Spitzer Science Center, Caltech), observers are circumventing this issue by using what they call the staring mode (avoiding large pointing jumps) and an algorithm to pick “sweet spot” pixels. Moreover, the results from the IRAC Data Challenge are helping to better understand its behavior. Giuseppe Morello (University College London), on the other hand, explained how his research group gets rid of instrumental effects from IRAC using machine learning. This method removes systematics from exoplanet transit data no matter if the noise source is from an instrument or a star. Speaking of transits, Kepler was one of the shining stars of this meeting. The original mission observed 150,000 stars continually for months during its first run, as it was designed to be a statistical mission. But can its findings be considered fully complete in planet radii and orbital periods? Joseph Catanzarite (SETI Institute) aims to answer this question by performing numerous simulations (“injections”) in order to validate our estimations of planet occurrence rates from transit data.

During Kepler’s primary mission, it was relatively easy to identify eclipsing binaries — which are a common type of false positive in exoplanet detection — owing to the spacecraft’s stability. Fergal Mullally (Kepler Science Office) points out that this is not true for K2, due to its continual drift from the pressure of sunlight. They are currently developing dave, a Python program that aims to find and vet planets from K2 data.

 

Another tool being developed for K2 data analysis is Robovetter, which was introduced by Susan Thompson (SETI Institute, NASA Ames). This new software will allow astronomers to fully and uniformly automate the creation of the final KOI (Kepler Object of Interest) catalog. And what about the science being done by K2? Jessie Christiansen (NASA Exoplanet Science Institute, Caltech) explains that it will not look for Earth-like exoplanets, but will instead be more flexible in the types of targets and their positions on the sky, allowing us to build a census of planets in the galactic plane.

Black Holes and Supernovae (by Ashley Villar)

There are still many open questions about supernovae and their progeny, black holes. Some of these questions will hopefully be answered by LIGO, though many will be solved using the electromagnetic radiation we detect from these sources.

Anthony Piro began the session by explaining his new models which trace the diffusive cooling of an initial supernova shock. His team has created an open source code, the SuperNova Explosion Code or SNEC, to allow others to explore a variety of explosion properties. Janie De La Rosa then spoke about her work on observing Type IIn supernovae (those with narrow emission lines in their spectra) at ultraviolet and optical wavelengths. These wavelengths are sensitive to progenitor models and the geometry of the surrounding material.

Cas A

Composite image of the supernova remnant Cassiopeia A, using data from the Chandra X-ray telescope, NASA’s Spitzer Space Telescope, and ground-based facilities. [NASA/CXC/SAO]

Following the exploration of progenitor geometry, Douglas C. Leonard spoke about his work in hunting for polarization in type IIP supernovae (those with long, plateaued light curves). A high degree of polarization implies asymmetry in the explosion itself, and he has been able to find such asymmetry in a number of type IIP supernovae. He pointed out that “bubble”-like structure (like what we see in the beautiful supernova remnant Cassiopeia A) might explain the polarization as well.

Switching gears, Karri Kolijonen spoke about an interesting X-ray binary (a binary consistent of a compact object and star that emits strongly in X-rays) known as GS 1354-64. This pair has an extremely short orbital period of just two and a half days! He explained how an instability in the black hole’s accretion disk might explain a recent outburst in the system.
Thomas Pannuti explained the basic morphologies of supernova remnants: shell, composite, and mixed. He has taken extensive, multiwavelength images of a mixed remnant known as W28 from radio through X-ray wavelengths. He notes that the radio masers in the remnant are offset from the X-ray light, although the significance of this is still an open question.
Finally, Maria Dainotti wrapped up the session with a discussion of long duration GRBs as standard candles. She finds that, like type Ia supernovae, the light curves of GRBs can be renormalized and standardized with a small scatter in their diversity. Because GRBs are so much brighter than type Ia supernova, these objects could be used as standard candles at much larger distances, and therefore probe the expansion of the universe at much earlier times.
Invisible black holes warp the space time around them in the center of a busy, dense cluster of stars.

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Wikipedia “Year of Science” Edit‐a‐thon (by Meredith Rawls)

What’s your first go-to source for an unfamiliar topic on the internet? If you said Wikipedia, you’re not alone. For many people, Wikipedia is the primary source of information about astronomy and science. However, many Wikipedia articles about science topics are incomplete or missing, and women are underrepresented among scientists with biographies.

To address this, the AAS Astronomy Education Board teamed up with the Wiki Education Foundation to host an edit-a-thon as part of the Wikipedia Year of Science. More than forty attendees spent the better part of three hours working through tutorials, creating new articles, and editing existing ones. The session was generously sponsored by the Simons Foundation.

The Year of Science initiative seeks to bring Wikipedia editing skills to the classroom and help new editors find sustainable ways to contribute to Wikipedia in the long term. Anybody can create a free account and start editing!

As a first-time Wikipedia contributor, I took the time to go through nearly all the tutorial exercises and familiarize myself with the process of editing a page. I decided to flesh out one section in an existing page about asteroseismology. Others created biography pages from scratch or selected various astronomical topics to write about. To me, the editing process felt like a cross between writing a blog post and a journal article, in a hack day type environment. Working through the tutorial and some examples renewed my empathy for learners who are tackling a new skill set for the first time. A full summary of our contributions is available. Altogether, we contributed nearly 13,000 words to 44 articles.

The Limits of Scientific Cosmology: The Way Forward (by Gourav Khullar)

After the town-hall with an open mic that raised exceptional questions in the morning, some of the pioneers of the field of scientific cosmology were here with their concluding remarks about the future of the field. John Carlstrom laid down the pipeline for future surveys that not only provide us with interesting constraints on current physics, but give us the opportunity to test new physics. He discussed the CMB, galaxy cluster growth, the Hubble constant and Baryonic Acoustic oscillations as parameters that would define our model of the universe cohesively in the future. The importance of facilities like LSST, SKA, DESI, CMB-S4 were discussed, and Carlstrom emphasized that over the next two decades these fantastic machines will decide the fate of scientific cosmology. Leonard Susskind followed this up with a theoretical framework of how the ideas of inflation and vacuum energy could lead to our understanding of whether String Theory could be the correct theory of the universe.

He touched upon multiverses with his analogy of ‘a submarine floating in a sea with just the right amount of buoyancy balancing gravity’ – a multiverse can have universes with different parameterized cosmological constants! Moreover, in Susskind’s opinion, the only true limit that inhibits our understanding of the features of our universe beyond the cosmic event horizon was the event horizon of an event or phenomena. Jim Peebles concluding this mesmerizing series of talks with his opinions on how physics ought to be direct and assertive with its theories, and should take pride in its explanatory power (or should it?).

 His comparison of local vs. high-redshift cosmology in terms of scales of problems was outstanding, and he encouraged the audience and the community to keep an open mind. After all, in Sean Carroll’s words, we do live in a “preposterous universe”, and the time is almost right to explain it all.

Press Conference: Black Holes and Gamma-Ray Bursts (by Susanna Kohler)

The final press conference of the meeting covered three topics from the categories of black holes and gamma-ray bursts.

Fred Rasio (CIERA/Northwestern University) opened the conference with a discussion of how the systems that LIGO detected might have formed. There are two primary models for how these black-hole binaries are created. In the first, they start out as binary systems of two massive stars. If the binary survives the process of both stars collapsing into black holes, then a binary black hole system results.
Rasio focused on the second theory, in which that black holes are formed in dense stellar clusters. These black holes then sink (via dynamical friction) to the centers of the clusters like dust particles settling on the floor of a room, where they form binaries in a “black hole mosh pit” — eventually getting kicked out of the cluster by dynamical interactions. You can read more about their research in the press release here.
black hole

The effects of a spinning black hole on the spacetime around it. [J.P. Eekels & J.M. Overduin]

Next up was Richard Henry (Johns Hopkins University), who spoke about the internal structure of spinning black holes (known as Kerr black holes). Because no light can escape from black hole interiors, we can’t learn what’s in them via observation. Instead, we rely on mathematical descriptions of what their interiors look like. Henry and collaborators have developed a new coordinate-invariant depiction of the structure of black holes that reframes how we think about visualize their interiors. More information can be found in their paper here.

The final press conference presentation was given by Maria Dainotti (Stanford University) on the subject of using gamma-ray bursts (GRBs) as standard candles. Standard candles are astrophysical sources that have known luminosities. We can use the light we observe from standard candles to estimate their distance, making them useful tools for testing cosmological models.
Type Ia supernovae (which always have roughly the same source brightness) are a typical example of a standard candle, and led to the discovery of dark energy in the 1990s. But if GRBs could be used in a similar way, they would be a much more powerful tool: they’re visible out to significantly further distances because they’re so bright. Dainotti and collaborators are analyzing a subset of GRBs from Swift observations that they term “gold GRBs”. By examining the correlations between parameters of these gold GRBs, Dainotti attempts to understand whether they can be used as standard candles.

Plenary Session: From the First Stars and Galaxies to the Epoch of Reionization: 20 Years of Computational Progress (by Gourav Khullar)

Mike Norman’s (University of California – San Diego) plenary talk concluded the AAS Plenary sessions with a treatise on the current generation of simulations that aim to characterize the first stars and galaxies that formed in the Universe.

Mike has been working in the field for a long time, and his collaborators’ work on the Enzo simulations is very well known. This talk was centered around some of the latest Enzo results, with a special emphasis on tracking down the Epoch of Reionization with a new series of runs called the Renaissance simulations. These runs focused on the most primeval galaxies ever formed in a cosmological box. Mike’s team uses Blue Waters, USA’s fastest supercomputer, situated in NCSA at Urbana-Champaign, Illinois (which also manages the large datasets coming out of the Dark Energy Survey!). The talk described the initial dark matter and gas dynamics along with a dark energy-supported metric evolution using simulations of a cosmic box that was the initial universe. The linear fluctuations of this ‘initial universe’ formed the first stars (called Population III stars in the astrophysics community) from hydrogen and helium generated in the Big Bang. Mike and his team established a catalogue of these first stars, and parameterized these into a function that modeled how these stars became the first galaxies, and eventually into the larger galaxies from the merger of smaller galaxy halos.

The statistics of these first galaxies (from the above mentioned Renaissance simulations) show that the first galaxies formed around a redshift of z = 20, roughly around the same time as the first stars, and way before the actual epoch of reionization (at z ~ 7, the concept is described here). The simulation results extended this evolution to the epoch of reionization and put interesting constraints on observations of this epoch, when we can actually see the ionized gas from this epoch in our observations. Investigations are ongoing, and Mike Norman’s team is positive that the Enzo simulations are here to stay for a long time, challenging and collaborating with observations along the way.

LIGO's second detection

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Plenary Session: The Elephant in the Room: Effects of Distant, Massive Companions on Planetary System Architectures (by Leonardo dos Santos)

The first session on Wednesday at 228th AAS Meeting was the Newton Lacy Pierce Prize Lecture by Heather Knutson (California Institute of Technology). This talk featured a broad range of research efforts on exoplanets, with the main focus on how we study the composition of their atmospheres, and how multi-body interactions carve the structure of the planetary systems we observe.

One of her first points is the well-known idea that the Solar System is an oddball, compared to the exoplanet systems we have found so far: most of these systems contain hot Jupiters and mini-Neptunes at very close-in orbits around their host stars. Moreover, even when studying their transmission spectra, it is difficult to know the exact composition of their atmospheres.

The main proposal on how these systems formed is the migration scenario. In order to validate this idea, Dr. Knutson and her group — The Friends of Hot Jupiters — study systems with close-in gas giants and their frequency of binary companions, which are supposed to be the main culprits causing gas-giant migration. They found that approximately half of the observed systems have long-distance companions, providing strong validation of the migration scenario. Moreover, Dr. Knutson speculates that wide binaries have more massive disks, which in turn produce more gas giants, populating our surveys with such planets.

Dr. Knutson shows that ~50% of hot Jupiters have long distance companions.

Dr. Knutson shows that ~50% of hot Jupiters have long distance companions.

Press Conference: Latest News from the LIGO Scientific Collaboration (by Michael Zevin)

On December 26th 2015, LIGO detected its second full-fledged gravitational wave event, dubbed GW151226 (the numbers signify the date it was detected). This detection along with the full results of LIGO’s first observing run were announced by Gabriela González, David Reitze, and Fulvio Ricci in the morning press conference. The masses of the two black holes are smaller than those of the first confirmed event (GW150914) – about 8 & 14 solar masses for GW151226 compared to 29 & 36 solar masses for GW150914. Though less visible by eye in the data, sophisticated search algorithms that match theoretically-produced templates of the gravitational waveform were able to extract it from the data and build up enough statistical confidence to declare it as a detection. The system was estimated to have merged at a distance of 1.4 billion light-years, and, due to its lower mass, stayed in LIGO’s detection band for a full second (5 times longer than the more massive GW150914).

Time-frequency plot of the second confirmed gravitational wave event - GW151226. Light colors represent higher energy.

Time-frequency plot of the second confirmed gravitational wave event – GW151226. Light colors represent higher energy.

This discovery further solidifies this nascent field into astronomy, and has given astronomers a new sense to explore the Universe. The next observing run of LIGO will commence later in 2016 and will be more sensitive due to system upgrade, increasing the rate at which LIGO should detect these types of astrophysical events. In addition, more detectors will be joining the network of gravitational wave observatories over the next few years, which will further constrain the location at which these events occur in the cosmos and increase the likelihood of detecting an electromagnetic counterpart to a gravitational wave event. More great discoveries to come!

Our zoo of stellar-mass black holes, including the 2 confirmed LIGO event, the 1 LIGO candidate, and indirect evidence from X-ray binaries.

Our zoo of stellar-mass black holes, including the 2 confirmed LIGO event, the 1 LIGO candidate, and indirect evidence from X-ray binaries.

Star Formation in a Range of Environments (by Benny Tsang)

David Cook began our morning star formation session with his work on the connection between the slopes of luminosity functions for star-forming regions and the host-galaxy properties. A moderate-strong trend was found: galaxies with higher star formation rate surface densities (the star formation rate per area projected on the sky) tend to have flatter luminosity functions. It was interpreted as the result of increased star formation efficiencies in high-density environments, which led to a large number of bright regions. Next, Daniel Carson presented his dissertation work on the observations of nuclear star clusters in disk galaxies. Radially-varying stellar populations were found. Stellar population modeling also revealed the star formation histories and stellar masses of the clusters. The stellar mass surface density of IC342 was measured to lie above the theoretical maximum set by stellar feedback.

Kaveh Vasei took us on his journey estimating the escape fraction of Lyman continuum photons from galaxies. He argued that the commonly used indirect methods in determining the escape fraction should only be interpreted as upper limits, and showed us the highest-resolution image of Lyman continuum leakers so far. David Guszejnov then led the first theoretical talk on modeling star formation using semi-analytical models – an approach between full-blown numerical simulations and pen-and-paper calculations. The advantage of such an approach is that you could explore different star formation models (with or without feedback) very quickly. The semi-analytical models with feedback reproduced observables such as the slope and turnover of the initial mass function well, and this technique can also further the understanding of binary-star formation.

Philip Hopkins then continued the theoretical discussion and showed that enough ionizing photons for cosmic reionization could be obtained if we consider binary stars. The idea is that material transfer within binary systems could extend the lifetimes of massive stars, thereby allowing them to produce enough ionizing photons before they die. Veronica Allen closed the session by sharing with us her work on characterizing the chemistry in the massive star-forming region G35.20-0.74N. An asymmetric distribution of nitrogen-bearing species was found, which could be due to disk fragmentation on unresolved scales and the formation of multiple sources with different ages.

Plenary Session: Observation of Gravitational Waves (by Susanna Kohler)

Gabriela González, spokesperson for the LIGO Scientific collaboration.

Gabriela González, spokesperson for the LIGO Scientific collaboration.

Following this morning’s exciting press conference, Gabriela González, spokesperson for the LIGO Scientific collaboration, gave the Kavli Foundation Plenary Lectureship. Though the Kavli lecture usually opens the AAS meeting, it was moved this week to accommodate the schedule for LIGO’s big announcement today!

González opened the plenary by digging a little further into the physics of LIGO detections. She described how the detectors work, pointing out that they’re designed to detect a strain of 1 part in 1021. This is roughly the same as measuring if the Earth-Sun distance changed by the size of a single atom!

Our ability to localize gravitational-wave detections currently relies on the timing of the observations: noting the difference in time between when the signal passes the LIGO Livingston and LIGO Hanford detectors (on the scale of 10 ms) can give us a broad sense of where in the sky the signal came from. Our ability to localize will significantly improve when future detectors like Virgo (Europe), LIGO-India, and KAGRA (Japan) come online within the next decade.

González spoke more about the detections that LIGO has made thus far. There were actually three significant gravitational-wave triggers in the first science run; the third has an 85% probability of being astrophysical, compared to the nearly 100% probability of the two official detections. The fact that there have been so many detections already — despite the fact that LIGO is only at 40% of its design sensitivity — suggest that we can expect many more to come!

As a final note, González pointed out that detections by ground-based gravitational-wave interferometers are only the start of gravitational-wave astronomy. Future observatories and missions (like eLISA, and improved-sensitivity pulsar timing arrays) will expand the search for gravitational waves to different frequency ranges.

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

The Limits of Scientific Cosmology: Setting the Stage: Accepted Facts, and Testing Limitations in Theory and Data (by Gourav Khullar)

With a stellar lineup of speakers to talk about current and future prospects of cosmology and its limits (or lack thereof), the first session kicked off with talks by Risa Wechsler, Joseph Silk, and Sean Carroll (his talk on Multiverses is described below, by Nathan Sanders). Risa set the stage with an elaborate description of the current accepted facts in the era of precision cosmology including the standard model of concordance cosmology, described by seven parameters and an accepted Lambda-CDM paradigm (with a cosmological constant and cold dark matter). The talk stressed on the fact that all these parameters are understood to a percent order precision, which is a remarkable deviation from the time in 1990s when according to Risa, “Alan Guth never thought that any of these numbers could be measured precisely!”

Risa Wechsler describing our current constraints on what Dark Matter could constitute.

Risa Wechsler describing our current constraints on what Dark Matter could constitute.

Joseph Silk discussing limits on cosmological parameters.

Joseph Silk discussing limits on cosmological parameters.

The CMB measurements, Big Bang Nucleosynthesis estimates and galaxy clustering statistics all contribute to locking down the description of our universe. She emphasized on the tensions between different probes to measure expansion rate H0 of the universe, and small scale predictions of cold dark matter simulations, but she is hopeful that these shall be resolved eventually. Joe Silk followed this up with his interpretation of trying to understand our place in the universe and placing limits on different parameters and scales that we measure, ranging from star masses to dark energy scale estimates.

By invoking the anthropic principle, Silk pointed out that perhaps multiverses could offer a potential solution to certain causes of concern in our current models. The future looked good, and according to Silk, a better characterization of non-gaussianities using powerful simulations and precise CMB measurements is the way to go.

The Limits of Scientific Cosmology: Normal Science in a Multiverse (by Nathan Sanders)

Slotted into the “contrarian” slot of this special session on the limits of cosmology, Sean Carroll (Caltech) made a powerful argument for the normalcy of the multiverse prediction of inflationary and other theories of cosmology. While other scientists, including earlier speakers in the session, suggested that the intense difficulty of collecting data directly testing the multiverse prediction disqualifies it as a “scientific” theory, Carroll argued that this is no different from the reality of the scientific process applied generally. He combats the absolutist interpretation of Karl Popper’s writing on demarcation, which implies that only imminently-falsifiable theories qualify as “scientific.” Instead, he points us to abduction as the fundamental motive of science, the idea that we seek to move towards the model that best explains the available evidence, closely related to Bayes’ theorem. He acknowledged that we may never collect enough evidence for our credence in the multiverse to converge to one, and yet it may definitely be true.  While he puts his own credence in the multiverse at “about 50%,” Carroll concludes that we should not reject the possibility of the multiverse out of hand solely on the basis of philosophical arguments.

Surprisingly, Carroll also comments that evidence can include both data and theory, specifically new interpretations of old ideas and new predictions. For example, Einstein did not make new observations of the precession of Mercury to lend credence (in the scientific sense) to his then-new theory of general relativity.  Instead, he applied his theory for the first time to the orbit of Mercury and demonstrated that it explains existing facts. In the same way, we may add or remove credence from the multiverse theory even without newly collected measurements on directly testable predictions.

Plenary Session: APOGEE: The New View of the Milky Way (by Nathan Sanders)

Jo Bovy (Toronto) spoke about a bevy of recent discoveries by the APOGEE team, which has collected half a million spectra of red giant stars throughout the Milky Way disk.  Bovy emphasized APOGEE’s unprecedented scope, covering close to half of the Milky Way disk and ranging ~10 kpc in radius, rather than the tiny neighborhood around the sun that most historical stellar surveys have probed.  Overcoming the challenges of galactic extinction, the APOGEE team has made the most precise measurement of the circular rotation velocity of the MIlky Way disk, v_c = 218 +- 6 km/s, and produced remarkable results on the chemical evolution history of the Galaxy.  In particular, they have shown that the star formation and chemical evolution history of the Galaxy seems to be remarkably constant throughout the disk. However, the radial migration of stars, which follows a non-circular orbit across the Milky Way’s spiral structure, causes mixing that makes the distribution of stellar parameters look uneven.  Bovy also emphasized the importance of open science, sharing data and code related to their work.  Like all SDSS data, the APOGEE spectra have been released publicly, and all their software pipelines and stellar models have also been made public.  Coming next is an APOGEE-2 survey of the Southern sky, a copy of the instrument to be installed at the DuPont telescope in Chile.

Press Conference: Dark Skies, Aliens, and the Multiverse (by Chris Faesi)

Tuesday afternoon brought another press conference to the AAS 228th meeting, this one taking us beyond the benign realms of planets, stars, and galaxies to Dark Skies, Aliens, and the Multiverse.

Earth at night

A view of Earth’s artificial light. [NASA Earth Observatory]

First, Eric Craine of STEM Lab, Inc. unveiled a new tool, the LANI (Light at Night Index), for measuring light pollution across a comprehensive sample of US communities: Using satellite data, LANI provides an estimate of the lighting efficiency in each US community having more than 500 people (comprising 19000+ cities and towns in total). The score incorporates the measured radiance (brightness), taking into account the number of people, the number of housing units, and the community area, and is then normalized to be between 1 and 100.  LANI can be used to assess where additional efforts are needed to improve energy efficiency and reduce light pollution, as well as to track changes in infrastructure and population over time. Read more about the LANI here.

Next, Evan Solomonides, an undergraduate student at Cornell University, presented a probabilistic analysis of the Fermi Paradox, the famous statement that asserts that if life is common in the Universe (as many believe), we should have detected it by now. The basic takeaway from his work is that while we’ve been sending powerful radio transmissions into space for the last 80 years, the volume of space reached by these transmissions is incredibly insignificant (perhaps 10 parts per million) compared to the size of our galaxy. If similar civilizations to ours have cropped up across the Milky Way and had even significantly longer timescales over which to send out signals, it is actually not surprising that we haven’t seen them yet, simply by virtue of the vastness of space. Solomonides predicts that it will be about 1500 years before it is probabilistically favorable to detect extraterrestrial civilizations, based on these assumptions.

Finally, cosmologist and science communicator extraordinaire Sean Carroll zoomed the focus out beyond the galaxy, beyond the observable universe, to the basic question of what it even means to do science in a multiverse. Carroll argued that even if a scientific theory is unable to be directly tested, it should not be automatically discarded as impossible or irrelevant. One cannot definitively prove that beyond the observable universe lie regions of space that have vastly different physical properties or cosmologies – in other words, the existence of a multiverse – and so this possibility should at least be philosophically considered by scientists, and the potential influences that the multiverse would have on the observable universe should be looked for.

Classification and Properties of Variables, Binaries and White Dwarfs and Stellar Evolution (by Ashley Villar)

In this era of big data, our ability to classify the plethora of celestial objects we detect is essential to our science. Gideon Bass began this session by discussing his work in using machine learning to classify Kepler variable stars. Bass ties together many machine learning algorithms to create a “Frankenstein” method to maximize accuracy. At higher energies, Saeqa Vrtilek discussed the use of color-color-intensity diagrams in X-ray wavelengths to classify objects such as cataclysmic variables, black holes and neutron stars.

Eclipse of Epsilon Aurigae.

Eclipse of Epsilon Aurigae by dusty disk.

Imre Bartos moved away from classification to discuss potential electromagnetic counterparts to black hole-black hole mergers. Specifically, stellar mass black holes near the center of galaxies are more likely to collide within only a million years due to friction. Richard Ignace discussed the polarization of Epsilon Aurigae. This odd binary undergoes eclipses about once every quarter of a century, when a dusty disk passes in from of the primary star, as shown above.

Tomomi Otani explained how we can look for planets and other companions around post main sequence stars, or stars which have finished burning hydrogen. One of the six targets (named PG-1219+534) from her survey in fact has a planet which has survived its host star’s drastic expansion as it reached the red giant branch. Finally, Paula Szkody explained the exotic light curves of cataclysmic variables found with K2. These detailed observations allow us to understand previously unseen bumps and wiggles in the light curves due to the complex physics driving these systems.

The Limits of Scientific Cosmology: Historical and Cosmological Context (by Gourav Koullar)

Karl Popper was everywhere today, being invoked by both Matt Stanley and Sean Carroll.

Karl Popper was everywhere today, being invoked by both Matt Stanley and Sean Carroll.

The second session of this forum constituted a series of talks aimed at setting the premise for our current understanding of the universe, and the very story of how cosmology came to be a science. Matt Stanley gave us an extraordinary tour of the last 150 years of scientific tendencies to create models of the universe. John Tyndall, James Clark Maxwell, Ernst Mach all joined the party, as we moved towards the Friedman-Lemaitre-Robertson-Walker model and Einstein’s tweaks to his field equations in General Relativity. Stanley gave due credit to the Steady State Cosmology ‘movement’, since it was using Popperian falsifiability that Hermann Bondi and Fred Hoyle established the rules of how a theory of the universe should look like. Even today, as we wage an internal battle between ‘Adaptive Optimism’ and ’Pessimistic Induction’ as scientists, our willingness understand the cosmos stays strong. 

Richard Dawid followed this up with a new philosophical theory of science, putting an emphasis on non-empirical confirmation of theories, and tracking evolution of credence (e.g. in a Bayesian manner) instead of definitive ‘true’ or ‘false’ answers to fundamental questions. Virginia Trimble brought the afternoon discussion to a conclusion by discussing a very unique empirical observation: whenever a community has come at a juncture where the choice has been between one or many, finite or ‘infinite’ (in a non-mathematical sense!), the latter has always won the debate. Whether we talk about a small Ptolemaic geocentric universe or a larger-than-life Copernican heliocentric solar system, the Milky way being the only galaxy vs. us being one of many, or a static versus an accelerating universe, the latter has been victorious. Hence Trimble asks, then who are we to stop at a universe, with existing ideas of a multiverse!

Stay tuned for tomorrow’s parts III and IV of The Limits of Scientific Cosmology!

Plenary Session: Things That Go Bump in the Night: The Transient Radio Sky (by Susanna Kohler)

This afternoon plenary was given by Dale Frail of the National Radio Astronomy Observatory, who injected some pop culture into our day by introducing radio transients as some of the night’s terrors that Game of Thrones warned us about.

Transient sources are those that change, often rapidly, while we observe them. Radio transients are an incredibly broad category, spanning sources that can vary on fraction-of-a-second timescales (like pulsars) to year-long timescales (like jets from active galactic nuclei).

In general, Frail emphasized, the radio sky is quiet; radio transients are actually quite rare. But the list of potential radio transients, while including many known sources, also pushes into more speculative territory. Interesting examples include the mysterious Fast Radio Bursts (FRBs) discussed in yesterday’s plenary by Maura McLaughlin, and electromagnetic counterparts to gravitational waves.
Frail gave an overview of what we currently know about the radio transients that we’ve observed — including where we find them, what energies they span within the radio band, and what timescales they vary on.
He also discussed the different strategies used to learn more about the transient radio sky: we’re generally faced with the choice to either “be a cartographer” by using all-sky surveys to search for new transients, or “be a buccaneer” by strategically following up on survey leads to localize and identify transient sources.

Frail argued that the way forward is to combine these strategies: use all-sky radio surveys coupled with rapid multi-wavelength follow-up. This combines the serendipitous element of surveys — the ability to find things we weren’t necessarily searching for, such as the first pulsar signal ever detected — with the higher-precision tools needed to identify what we’re looking at.

Plenary Session: MAVEN Observations of Atmospheric Loss at Mars (by Meredith Rawls)

One of the best ways to learn about exoplanets is by carefully studying planets much closer to home. Shannon Curry emphasized this throughout her presentation about Mars’ atmosphere, which was motivated by the fact that Mars used to be a warmer, wetter planet. The Mars Atmosphere and Volatile Evolution orbiter (MAVEN) arrived at Mars in September 2014 and has been collecting many kinds of data about the Martian atmosphere ever since.

Several different processes are responsible for Mars losing parts of its atmosphere to space. Because Mars is a relatively small planet, it has had a difficult time holding onto its atmosphere over the history of the Solar System. Neutral particles, ionized particles, and even water vapor all find unique ways to escape the grip of Mars’ gravity. In addition, the variable effects of the Solar wind and other space weather affect what kind of material is lost.

Beyond the detailed physics and chemistry illustrated above, the differences in Mars’ atmosphere as a function of the Sun’s behavior are a challenge to observe because the Sun is experiencing a quiet solar maximum with relatively few coronal mass ejections. Thanks to MAVEN, we have the first opportunity to measure these processes up close. Mars serves as an excellent analog for exoplanet hydrogen loss and can tell us whether similarly-sized planets are likely to have the same fate.

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Plenary Session: The Galaxy Zoo (by Benny Tsang)
Galaxy Zoo was so hot that the servers hosting the galaxy images got melted down soon after being launched.

Galaxy Zoo was so hot that the servers hosting the galaxy images got melted down soon after being launched.

Kevin Schawinski from ETH Zurich took us on a tour of his wonderful Galaxy Zoo. It is a huge zoo with about a quarter million zookeepers, citizen astronomers who collaboratively classify galaxies by their looks in an attempt to understand galaxy evolution. The big question that is being answered is: how do blue, actively star-forming galaxies evolve into red, quiescent (non-star-forming) galaxies? The Zoo helped reveal that blue galaxies turn into red galaxies via two possible paths: 1) galaxies might run out of their gas supply and shut off star formation slowly, or 2) galaxies could merge with one another and turn off star formation by destroying the gas reservoir rapidly!

The Galaxy Zoo project also led to the discoveries of:

  • “Green Peas”: the “living fossils” of galaxy evolution. These are compact, bright, green galaxies that are actively forming stars.
  • Overlapping galaxies: pairs of galaxies that are separated physically but happen to lie on the same line of sight. These provide excellent laboratories for studying dust extinction.
  • “Hanny’s Voorwerp”: an unusual object named after Hanny van Arkel, the discoverer. This is believed to be the first detection of a quasar light echo.

Galaxy Zoo’s idea to get help from citizen scientists was further extended into an award-winning project known as the Zooniverse, which is an online platform for streamlined crowd-sourcing for scientific research that requires human input. As the future of astronomy is going to be extremely data-rich, the Galaxy Zoo project has also explored combining the help from citizen scientists with machine learning to analyze extremely large datasets.

Extrasolar Planets: Atmospheres (by Leonardo dos Santos)
Antonija Oklopčić (Caltech) explains that Raman scattering of light, which works similarly to Rayleigh scattering (the process that makes Earth’s sky blue), can be used in the future to study the atmospheres of exoplanets. Her work is to create model spectra containing these features, from which we can learn about the presence and altitude of atmospheric clouds. Dr. Carl Melis (University of California, San Diego) studies the inner composition of exoplanets by looking at their remnants after they are destroyed by a dying star. His most recent work suggests that there is a differentiated pollution (from the core and the crust of a planet) in the disk orbiting of a white dwarf star. Samuel Grunblatt (University of Hawaii) introduces us to the main subject of his thesis: a hot-Jupiter observed by Kepler’s K2 mission transiting an evolved, red giant star. They used some pretty tricky data analysis in order to filter out the noise intrinsic to this type of star.
IMG_0274

Grunblatt shows the K2 transit before and after removal of granulation effects.

Avi Shporer (JPL) asks the question: why are hot Jupiters so large? His research aims to study the correlation between stellar irradiation and planetary radius, and in order to have a more complete picture, they need to detect more gas giants on lower stellar irradiation regions. This idea gave rise to LCOGT K2 Warm Jupiter project, which recently discovered a brown dwarf in a long-period orbit around a Sun-like star. Paul Mason (New Mexico State University) proposes that the Milky Way is evolving to a more habitable galaxy, due to the expansion of the universe, the processing of heavier material inside stars, and the general decrease of ionizing radiation.

Evolution of Galaxies (by Ben Cook)
Tuesday morning’s panel on the lifecycles of galaxies began with a talk by Ben Cook (astrobites author) on how we can infer whether a galaxy experienced large mergers. Cook used the Illustris simulation to study how stars are left in so-called “stellar halos” far outside galaxies after they have large collisions. Yicheng Guo then showed evidence that lower-mass galaxies tend to form their stars in a few large bursts, rather than long, steady formation like in more massive galaxies. Ali Khostavan measured the strengths of particular emission lines, which are found to increase further back in time, telling us that galaxies were forming many more stars early on in the universe than they are now.

 

Artist's impression of the heart of an active galaxy, known as an Active Galactic Nucleus (AGN). [NASA/Goddard Space Flight Center Conceptual Image Lab]

Artist’s impression of the heart of an active galaxy, known as an Active Galactic Nucleus (AGN). [NASA/Goddard Space Flight Center Conceptual Image Lab]

Irene Shivael presented a new measurement of the relationship between the star-formation rate of a galaxy and the mass of its stars (i.e., its stellar mass). This relation has been measured to have very different values by a large number of different studies! Gene Leung look at the spectra of Active Galactic Nuclei (AGN) and found that many of them are blowing out large blobs of gas into the space around their host galaxies. This process is an important part of how we think galaxies shut off their star formation: the AGN blow the gas far away, so it cannot collapse and form new stars.

 

Rui Xue studied large glowing halos of Lyman-alpha emission that are seen around high-redshift galaxies. This emission is lighting up the gas around each galaxy and can be used to measure the “circum-galactic medium,” the stuff around galaxies extremely far away. SungWon Kwak ran new simulations to study how small (dwarf) galaxies can form central bars or spiral arms when they fall into clusters or collide with other galaxies. Dusan Keres closed out the session by talking about a new, very powerful simulation called FIRE, which uses very complicated star-formation models and tries to model galaxies with as high resolution as possible.

 

Small Telescope Research Communities of Practice (by Ashley Villar)

Although astronomers are building larger and larger telescopes to study the farthest reaches of space, recent advances in camera technology are opening the gates for backyard enthusiasts to explore cutting-edge science. Dave Rowe opened the session with a short talk on a technique called speckle interferometry. In short, this technique takes many quick (short exposure) images and averages them using the Fourier power spectrum of the images. This technique lets you separate stars a half arcsecond apart on the sky, or about 1/120th the size of the moon, for a few hundred dollars! Next, Dominic Ludovici explained how his research is bridging the gap between professional and ameateur spectroscopy by utilizing instruments called collimated grisms. Using custom 3D-printed parts, Ludovici is able to take high-quality spectra of everything from Wolf-Rayet stars to quasars for only a few hundred dollars. These tools allow Ludovici to bring science into his college classrooms at the University of Iowa through a series of hands-on observing labs. Virginia Trimble wrapped up the session with some thoughts on communities of practice and collaborations. She underscored the importance of creating an open and welcoming environment for incoming members of any collaboration, and she emphasized that we should build communities of inclusion.

Press Conference: Shaking Hands and Eruptive Variables (by Meredith Rawls)
Tuesday morning’s press conference highlighted two new papers. First, Brandon Carroll from Caltech and Brett McGuire from NRAO presented the first detection of a chiral molecule, propylene oxide, outside our Solar System. Chirality, or “handedness,” is a special property of some molecules that are found in one of two mirror-image versions. Chiral pairs generally have the same properties but different kinds of physical interactions. Biology has a tendency to prefer sugars and proteins that are one chirality only, but it is unknown whether this is a universal preference or a quirk of Earth-based life. Carroll and McGuire’s new detection in a star-forming cloud of material near the center of the Milky Way does not distinguish whether the propylene oxide is left- or right-handed, but it does show that the cosmos is capable of producing complex molecules that are essential to biology. In the future, they hope to use polarized light to directly measure chirality.

Next, Joel Green from STScI presented how a young star surrounded by a bright protoplanetary disk, FU Orionis, has changed since a bright outburst in 1936. Since then, it has consumed some 80 Jupiter’s worth of material! By comparing observations of the disk’s brightness taken twelve years apart, Green showed that the hottest inner regions of the disk have faded significantly while the cooler regions farther out have not. In other words, the star has consumed the hot parts of the disk closest to it and altered the chemical composition in the disk that remains. This is likely what our own Sun experienced as a young star, and has implications for planet formation because the chemical composition of the disk affects what materials are available for forming planets. Green hopes that future observations with the Webb telescope will complement existing Spitzer and SOFIA data.

Mt Etna

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Plenary Session: From Space Archeology to Serving the World Today: A 20-year Journey from the Jungles of Guatemala to a Network of Satellite Remote Sensing Facilities Around the World (by Michael Zevin)

In the conference’s second plenary session, NASA’s Daniel Irwin turned the eyes of the conference back to Earth by highlighting the huge impact that NASA missions play in protecting and developing our own planet.

Irwin came to be involved in NASA through his work mapping Guatemalan jungles, where he would spend 22 days at a time exploring the treacherous jungles on foot armed with a 1st generation GPS, a compass, and a machete. A colleague introduced Irwin to the satellite imagery that he was exploring, demonstrating how these images are a strong complement to field work. The sharing of this satellite data with nearby villages helped to show the encroachment of agriculture and the necessity of connecting space to the village. Satellite imagery also played a role in archeological endeavors, uncovering dozens of Mayan cities that have been buried for over a millennia by vegetation, and it provided evidence that the fall of the Mayan civilization may have been due to massive deforestation that led to drought.

IMG_1760

Glacial retreat in Chile imaged by ISERV.

Irwin displayed the constellation of NASA’s Earth-monitoring satellites that have played an integral role in conserving our planet and alerting the world of natural disasters. He also showed images from the The ISS / SERVIR Environmental Research and Visualization System Completed Operations (ISERV, which Irwin claimed as the instrument acronym that contains the most acronyms). ISERV is a monitoring camera aboard the ISS with 4m resolution of the ground and a 14.5 km by 10 km field of view. This camera is able identify indications of natural disasters to give early-warnings to areas that are potentially threatened, and help analyze disaster aftermath to aid in recoveries. Particularly striking was an image of the retreating glaciers in Chile due to rising global temperatures. 47,000 such images are available to the public at http://earthexplorer.usgs.gov/! The contributions by NASA to the well-being of our planet and civilization are certainly staggering.

110: Galaxy Clusters (by Ben Cook)

A short session on clusters of galaxies began with X-ray observations by David Buote studying the distribution of mass in a cluster. By measuring the X-ray temperature (using the spectral information) and the intensity of X-rays, Buote derived the amount of gas in each part of the cluster. By assuming hydrostatic equilibrium, this lets you derive the total mass (not just the gas, but also the stars and dark matter!) of the cluster. But it’s unclear so far whether that assumption is valid here. Jack Burns followed this up by discussing the ways we can observe the wreckage when galaxy clusters merge together. These mergers, as Burns puts it, are “the most energetic events since the Big Bang”. When two clusters crash together, their gas is heated to very high temperatures, producing radio emission that is visible as “radio relics”. Reinout Van Weeren used similar observations in the radio to attempt to measure the magnetic fields in a few clusters. Christine Jones looked at the two primary ways of locating clusters — through X-rays and through the Sunyaev–Zel’dovich (SZ) effect in the radio — and concluded that the two methods are different: one method will easily find clusters the other is less likely to see, and vice versa. Angela Berti detected the signal of “galactic conformity” all the way to redshift z=1, an effect that makes galaxies more likely to be found around neighbors that are very similar (in terms of color or shape) than different kinds. Georgiana Ogrean closed the session by showing a merger between two galaxies that is not producing a strong shock front.

112: Astronomy Education for All: The 2017 Eclipse, Accessibility and NASA (by Meredith Rawls)

This afternoon session kicked off with an advertisement for US-based astronomers’ favorite upcoming event: the 2017 Solar Eclipse. Jay Pasachoff reviewed plans for the August 21, 2017 event and pointed us to resources about choosing the best viewing site and what to expect on the momentous day. We also heard from Denise Smith, Jim Manning, and Daniel McIntosh about various NASA-funded efforts for education and outreach in the classroom and beyond.

The other two talks from this session focused on the newly-formed AAS Working Group for Accessibility and Disability and what the astronomical community can do to cultivate a more accessible culture. Speakers Jackie Monkiewicz and Lauren Gilbert described how and why inaccessibility is driving people away from the field: by requiring people with disabilities to disclose those disabilities, by maintaining inaccessible buildings and observatories, by acting inappropriately when accommodations are requested, and by not working well in advance of a course or event to anticipate the needs of people with disabilities. To learn more about what you can do to make astronomy accessible, and what efforts are already underway (including right here at AAS 228), see these resources compiled by AstroBetter.

Press Conference: From Molecules to Galaxies (by Leonardo dos Santos)

Chris Arumainayagam (Wellesley College) opens up the press conference with a research being carried on exclusively by undergraduate students. He shows that the formation of complex molecules in space is currently explained by high energy cosmic rays and ultra-violet (UV) photons, but then presents their suggestion that low-energy UV photons may also play a significant role in this process. Additionally, if detected, the presence of the molecule Methoxymethanol could help to prove their hypothesis.

IMG_0262 (1)

Philip Hopkins showing results from press release.

Philip Hopkins (Caltech) shows the work on FIRE, a new galaxy evolution simulation that is pushing the limits of the field, and is very successful in resolving some of its biggest issues, such as the abundance of fluffy galaxies, the cold dark matter hypothesis and the missing satellites problem.

Gregory Walth (University of California, San Diego) and collaborators discovered an unexpected giant luminous star-forming clump on a galaxy at redshift z = 0.61 — which, incidentally, is gravitationally lensed by the galaxy cluster Abell S1063 (z = 0.35). Such clumps are much more common at higher redshifts (z > 2), so this discovery raises questions on how common these objects are in the more local universe, and how they were formed.

Plenary Session: The Brightest Pulses in the Universe (by Michael Zevin)

Fast radio bursts are one of the biggest mysteries in modern astronomy. Attempts to explain their astrophysical origin span from the merging of relativistic objects to pesky aliens (one of these explanations is more accepted than the other). Maura McLaughlin took the audience on a walk through the history of FRBs and how we’ve built our current understanding of these perplexing occurrences.

The story started with the discovery of radio pulsars by Jocelyn Bell in 1967. Due to the periodicity of the radio beam in these newly-discovered objects, the time-series data of the radio sky was almost always Fourier transformed before analysis and burst events were lost in this transformation. McLaughlin believed that FRBs could have been detected as early as the 1970s if this were not the case! The story then jumped ahead to the 2000s, when astronomers (including McLaughlin) took a look back at archival data from as early as 1967 to search for short duration radio transients in our galaxy. In 2007, a Parkes telescope search for such objects in the Small Magellanic Cloud found a very bright radio burst with a strikingly high dispersion measure (which can be correlated to distance) – the first FRB candidate!

figure

McLaughlin admits that even she had her doubts about the astrophysical origin of the Lorimor Burst.

This became known as the Lorimer Burst, and though some skepticism about its astrophysical origin pervaded over the next few years (primarily because to microwave ovens…no joke), the discovery of more FRBs using Parkes, Arecibo, and Green Bank Telescope after 2013 solidified these events as full-fledged astrophysical phenomena! A very recent study (published in 2016) even found that FRBs can repeat, with no obvious periodicity.

 Though there are many theories as to what might cause FRBs, it is clear that there is no viable model that we know of to explain all FRBs. McLaughlin did, however, confirm that hungry aliens operating microwaves is energetically unrealistic.

Editor’s Note: This week we’re at the 228th AAS Meeting in San Diego, CA. Along with a team of authors from astrobites.com, I will be writing updates on selected events at the meeting and posting twice each day. Follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

Come visit Astrobites at the AAS booth ... we have swag!

Come visit astrobites at the AAS booth … we have swag!

Things kicked off last night at our undergraduate reception booth. Thanks to all of you who stopped by — we were delighted to hear from undergrads who already know and love the site, educators who want to use it in their classrooms, and students who had not yet been introduced to astrobites and were excited about a new resource!

For the rest of the meeting we will be stationed at the AAS booth in the exhibit hall (booth #211-213), so drop by if you want to learn more (or pick up swag: we’ve got lots of stickers and sunglasses)!

Monday morning was the official start of the meeting. Here are just a few of the talks and workshops astrobiters attended this morning.

Opening Address (by Susanna Kohler)

AAS President Meg Urry kicked off the meeting this morning at 8am with an overview of some of the great endeavors AAS is supporting. We astrobiters had personal motivation to drag ourselves out of bed that early: during this session, Urry announced the new partnership between AAS and astrobites!

Urry touched on some difficult topics in her welcome, including yesterday’s tragedy in Orlando. She reiterated the AAS’s support for the Committee for Sexual-Orientation and Gender Minorities in Astronomy (SGMA). She also reminded meeting attendees about the importance of keeping conference interactions professional, and pointed to the meeting’s anti-harassment policy.

Partnership Announcement (by Michael Zevin)

This morning, the American Astronomical Society announced the new partnership that it will have with Astrobites! We are beyond excited to embark on this new partnership with the Society, which was the culmination of several years of supportive interaction. This new relationship is described further in the press release just issued by AAS.

First plenary: The Ocean World Enceladus (by Chris Faesi)

Enceladus lineup

Enceladus takes its place in the lineup of potential life-bearing solar system bodies.

In the first plenary session of the AAS 228th meeting, Christopher Glein of the University of Toronto took the audience on an exciting tour of the ocean world Enceladus. This small, icy moon of Saturn had been thought rather unremarkable for most of the 2+ centuries since its discovery in 1789, but the Cassini spacecraft’s extended visit over the last decade has revealed it to be a surprisingly dynamic and unique little world. From Cassini’s 23 flybys, we now know that Enceladus is composed of roughly equal parts rock and ice, and, with an albedo of 99%, is the most reflective body in the solar system.

The moon’s surface is not entirely cratered, as are most solar system objects such as our own Moon, but has a southern hemisphere with long fissures that look like tiger stripes on an otherwise smooth surface. Follow-up with the satellite’s highly sensitive instruments revealed that these stripes were heated up to 200 K – much hotter than Enceladus’s typical 75 K surface temperature. There seems to be an energy shortage: the heating expected from Saturn’s tidal influence on the moon is a factor of about ten smaller than what would be required to heat the surface this much. Unraveling this discrepancy is still an area of active study today.

Enceladus also spews powerful jets of salty water and water ice far into space via cryovolcanism, making it the smallest geologically active body in the solar system. Perhaps most intriguingly, this 500 km-diameter moon may be a promising target in the search for extraterrestrial life. The jets are highly alkaline and may contain molecular hydrogen, which links the inorganic and living worlds as a reactant and energy source. Although Cassini’s very fruitful mission will come to a close in 2017 with a death spiral into Saturn, the future is still bright for Enceladus. Glein closed with a preview of the next mission to this special moon: “ELF”, the Enceladus Life Finder, will fly through and analyze Enceladus’s icy plume in unprecedented detail using state-of-the-art instruments and is predicted to fly in 2031.

102: The NASA K2 Mission (by Meredith Rawls)

Everyone’s favorite planet finding telescope continues to impress. In this morning session, we heard highlights about how the repurposed Kepler mission (K2) is contributing to research in areas ranging from nearby brown dwarfs to extragalactic supernovae. The session kicked off with an overview by Knicole Colon, who happily reported extended funding for K2 through 2018, when its fuel is projected to run out.

Bradley Tucker discussed recent extragalactic results from K2, and supernovae in particular. So far, the Kepler Extragalactic Survey has found 17 supernovae and they hope to find at least 20 more in the next three years. Because Kepler observations are so frequent, they reveal previously hidden subtleties in how supernovae fade over time.

Of course, exoplanet science is still a primary goal for the K2 team. Matthew Penny updated us on the status of the in-progress microlensing campaign, which uses Kepler to search for one-off brightening events that indicate the presence of a planet due to gravitational microlensing. Work is also underway by Jeffrey Coughlin and colleagues to improve our ability to automatically detect and confirm exoplanet candidates with the traditional transit technique. They have developed a robotic technique called DAVE (Discovery And Vetting of K2 Exoplanets), which does an impressive job of eliminating false positive eclipse signals. To complement K2 observations of exoplanet transits, astrobites alumna Courtney Dressing presented a method which incorporates observations from the infrared Spitzer Space Telescope to better refine planet properties such as radius.

One of the challenges of K2 compared to Kepler is noise introduced by the spacecraft’s less precise ability to point. Derek Buzasi implored us to not consider any one pipeline that removes this jitter as necessarily “best,” but rather to try several and recognize that different science goals will need different approaches to data processing.

Jeffrey Van Cleve showed examples of what can be accomplished when K2 data is appropriately processed: just like Kepler, K2 can use asteroseismology to see the ringing oscillations of acoustic waves inside evolved stars.

Finally, several speakers including Buzasi presented their work on stellar astrophysics with K2. In addition to stellar activity and asteroseismology, presenters discussed spots and flares on cool brown dwarfs (John Gizis) and using eclipses together with stellar models to measure distances to star clusters (Keivan Stassun). Not a bad roundup for a broken space telescope!

103: Galaxies Big and Small (by Ben Cook)

This session (one of the first parallel sessions of the conference) included a variety of presentations studying galaxies, primarily using observations but ending with a unique purely analytical study. Stephen McNeil began the session by discussing a survey looking for dwarf galaxies in “voids” — the most empty spaces in the universe. Candidate objects can be looked for using a smart choice of photometric color bands, but more work is ongoing to confirm the locations of (and distances to) the objects with spectroscopy. Aaron Romanowsky gave an overview of the field of Ultra-Diffuse Galaxies, a new class of galaxies only discovered within the last 2 years. Some of these galaxies are as large as the Milky Way and seem to have almost as much dark matter, but they contain 1000x fewer stars.

A high-redshift galaxy which is "gravitationally lensed" by a large cluster is shown to the left. The right image shows how big it would look without the magnification. [Slide by Greg Walsh]

A high-redshift galaxy which is “gravitationally lensed” by a large cluster is shown to the left. The right image shows how big it would look without the magnification. [Slide by Greg Walsh]

Greg Walsh presented a longer “dissertation presentation” on his work observing dusty star-forming galaxies. One of the best tools for this job is using galaxy clusters as gravitational lenses to help magnify very distant galaxies. Tianxing Jiang showed a variety of observations and simulations that suggest that the level star formation in a galaxy may have to do with the amount of gas pressure, and Aaron Barth showed new measurements of the masses of Super Massive Black Holes using radio measurements. Barth argues that the key to getting good (10%) accuracy is having very high spatial-resolution.

Bill Forman discussed how many galaxies have extremely hot, ionized gas surrounding them, and Bruce Rout argued that dark matter may not be necessary to explain the rotation curves of galaxies; a complicated analytical model using general relativity can do the job without any dark matter at all.

Press Conference: Exoplanets and Brown Dwarfs (by Susanna Kohler)

The first press conference of the meeting featured four speakers discussing some of the latest developments in the field of exoplanet and brown dwarfs.

rocky body surface

Artist’s impression of the surface of a massive, planet-like body being devoured by a white dwarf. [A. Hara/C. Melis/W. M. Keck Observatory]

First up was Carl Melis (UC San Diego), who discussed the discovery of a rocky exoplanetary body currently being shredded by a white dwarf. As the white dwarf’s strong gravitational pull tears the body apart, we can observe the material pulled from its surface layers. These observations — made by Keck Observatory and Hubble — indicate that the body might have been Earth-like, with an outer surface of made up of limestone. Here’s the press release.

Next, Avi Shporer (NASA Jet Propulsion Laboratory) spoke about the first transiting brown dwarf found in K2 mission data. Stars like companionship, but the companions are usually other massive stars, or Jupiter-size or smaller planets. Companions with the mass and size of brown dwarfs are uncommon, leading to the term “brown dwarf desert”. The brown dwarf found by K2 marks the 12th transiting brown dwarf we have discovered.

Jerome Orosz (San Diego State University) was up next, presenting the largest and longest-period circumbinary planet yet discovered. This planet is in an orbit with a 3-year period around a two-star binary system (think Tatooine!). This is the longest orbital period of any confirmed transiting exoplanet, and this Jupiter-sized planet, which is in the circumbinary’s habitable zone, is the largest circumbinary planet we’ve observed. Here’s the press release.

Finally, Sean Mills (University of Chicago) spoke about Kepler-108, a giant planet system in which the two exoplanets don’t orbit within the same plane. This is detectable because the transits of these planets occur at different times and have different depths in the light curve each time they orbit. Their misalignment may have been caused by a past collision with another planet, which was kicked out of the system in the process.

The LIGO-VIRGO Forum on Hunting Gravitational Wave Counterparts (by Gourav Khullar)

This parallel session, organized by Peter Shawhan (University of Maryland, advancedLIGO) discussed the first major followup campaign of the GW150914 gravitational wave (GW) discovery event by the physics and astronomy community around the world. It was extremely exciting to hear the speakers talk of the actual process behind the mega-collaborative effort following the first GW event. news_project_07032016b_lgThis paper, published on June 3rd this year, was described by Peter, with a strong emphasis on the timeline following the GW alert in raw LIGO data back in September 2015, along with description of the sky map and raw data given to different facilities and collaborations that LIGO-VIRGO had signed Memorandums of Understanding (MOUs) with for rapid and robust followups. The talk also focussed on resources and tutorials available now to unpack and characterize future alerts data from LIGO-VIRGO. This talk was followed by the description of the all sky survey PAN-STARRS, and its joint efforts with LIGO. It was pointed out that PAN-STARRS had already scanned the sky multiple times, which gave the program an edge in determining transients, i.e. recent features appearing on their new maps but not the old. This extensive survey also allowed better characterization of the transient source, which would be the next step for PAN-STARRS and other similar projects.


Following this was a talk by Andy Howell, of the newly formed Las Cumbres Observatory – A Global Telescope Network (LCOGT), made up of multiple telescopes across the US, Chile, Spain, South Africa, China and Australia. Howell emphasized that a robotic pointed-search facility could be extremely crucial in automated alert triggering of GW events in the future. Their galaxy and transient catalog is one to look out for.

Greetings from the 228th American Astronomical Society meeting in San Diego, California! This week, along with a team of fellow authors from astrobites, I will be writing updates on selected events at the meeting and posting twice each day. You can follow along here or at astrobites.com, or catch our live-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resume next week.

If you’re at the meeting, come stop by the AAS booth (Booth #211-213) to learn about the newly-announced partnership between AAS and astrobites and pick up some swag. And don’t forget to visit the IOP booth in the Exhibit Hall (Booth #223) to learn more about the new corridors for AAS Journals and to pick up a badge pin to represent your corridor!

corridors

1 … 17 18 19 20 21