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jellyfish galaxy

Feeling jelly? This detailed image (click for a wider view) reveals the molecular gas in the long tail of the jellyfish galaxy ESO 137-001. In this image, red emission is molecular gas newly detected with the Atacama Large Millimeter/submillimeter Array (ALMA), green shows MUSE Hα emission, and the background image (blue, green, and red) shows the galaxy as imaged by the Hubble Space Telescope. This jellyfish galaxy is located 220 million light-years away in the Norma galaxy cluster, and its tail is caused by ram pressure stripping — the stripping of its gas as the galaxy falls through the surrounding intracluster medium, the material that lies in the space between galaxies. In a new publication led by Pavel Jáchym (Astronomical Institute, Czech Academy of Sciences), astronomers present ALMA’s unprecedented high-resolution maps of this jellyfish galaxy’s molecular-gas tail and show how this helps us to understand star formation in these dynamic, intense environments. To learn more about star formation in cosmic jellyfish (and to view the full original image), check out the article below.

Citation

“ALMA Unveils Widespread Molecular Gas Clumps in the Ram Pressure Stripped Tail of the Norma Jellyfish Galaxy,” Pavel Jáchym et al 2019 ApJ 883 145. doi:10.3847/1538-4357/ab3e6c

hydrocarbons in Titan's atmosphere

This illustration shows some of the molecules that have been discovered in the hazy atmosphere of Saturn’s largest moon, Titan. Though nearly 98% of Titan’s stratosphere is molecular nitrogen, there’s just enough methane — CH4 — for some interesting chemistry to happen when ultraviolet light is thrown into the mix. After this light breaks apart the methane molecules, complex hydrocarbons can form as these newly freed fragments link together in chains. A team of scientists led by Nicholas Lombardo (U. of Maryland, NASA Goddard SFC, Yale U.) has now made the first unambiguous detection on Titan of a hydrocarbon known as propadiene (CH2CCH2; also called allene). This colorless, flammable gas had, before now, never been detected beyond Earth. Scientists believe that Titan’s atmosphere may resemble Earth’s primordial atmosphere, so understanding its component molecules is an important step to learn more about how our own planet evolved. To read more, check out the original article below.

Citation

“Detection of Propadiene on Titan,” Nicholas A Lombardo et al 2019 ApJL 881 L33. doi:10.3847/2041-8213/ab3860

ion loss and magnetic obliquities

How does tilting a planet affect its ability to hold on to its atmosphere in the face of intense stellar radiation? The above images are from a series of numerical simulations run by a team of scientists led by Chuanfei Dong (Princeton University), which explore the role of magnetic obliquity — the tilt of the planet’s magnetic field — in regulating the loss of ions from an exoplanet’s atmosphere. In particular, Dong and collaborators modeled Earth-like planets in the habitable zones of two different host stars: a Sun-like G dwarf (top row) and a TRAPPIST-1-like M dwarf (bottom row). The simulation frames above show the ion loss from these two planets with four different tilts: 0°, 45°, 90°, and 135° (columns from left to right). While obliquity doesn’t much affect mass loss for a planet around a Sun-like star, the planet around the M-dwarf loses twice as much mass when its obliquity is oriented at 90° than it does when it’s aligned at 0° — which could matter for such a planet’s potential habitability! For more information on the authors’ conclusions, check out the article below.

Citation

“Role of Planetary Obliquity in Regulating Atmospheric Escape: G-dwarf versus M-dwarf Earth-like Exoplanets,” Chuanfei Dong et al 2019 ApJL 882 L16. doi:10.3847/2041-8213/ab372c

disk dominated galaxy

What drives galaxies into different shapes and structures? To answer this question, we have to understand how the different components of galaxies form. In general, galaxies are made up of two main parts that form in different ways: a thin disk of stars, gas, and dust; and a thick spheroid of stars comprising a dense bulge and sparser halo. In a new study led by Min-Jung Park (Yonsei University, Republic of Korea), a team of scientists used a high-resolution cosmological simulation to explore these components of massive galaxies in more detail. In the image above, you’re seeing two views — face-on (top) and edge-on (bottom) — of a simulated massive, disk-dominated spiral galaxy. The left-most panels show the whole galaxy; the middle and right panels show the galaxy deconstructed into its spheroid (middle) and disk (right) components. By looking at these components separately, Park and collaborators are able to learn more about the processes that form these different parts of galaxies, shedding light on what causes galaxies’ final structures. To learn more about the authors’ conclusions, check out the article below.

Citation

“New Horizon: On the Origin of the Stellar Disk and Spheroid of Field Galaxies at z = 0.7,” Min-Jung Park et al 2019 ApJ 883 25. doi:10.3847/1538-4357/ab3afe

silicate grains

How do molecules form in the hostile environments of the circumstellar and interstellar medium? Laboratory experiments are helping us to better understand this process! The image above (click for the full view) shows a high-resolution electron microscopy image of the complex surfaces of silicate grains, representative of dust grains found in the space around and between stars. In a new study led by Alexey Potapov (Max Planck Institute for Astronomy, Germany), scientists deposited thin layers of carbon dioxide and ammonia ices on nanometer-sized silicate and carbon grains and explored the subsequent chemical reactions under conditions similar to those of the interstellar medium. In the team’s experiments, the reactions that form complex organic molecules happened three times as fast in the ice on the surface of dust grains as they did in the ice alone. This catalytic effect of dust surfaces is an important piece in the puzzle of how complex molecules — and ultimately, life — formed in our universe. You can read the full article below to find out more!

Citation

“Evidence of Surface Catalytic Effect on Cosmic Dust Grain Analogs: The Ammonia and Carbon Dioxide Surface Reaction,” Alexey Potapov et al 2019 ApJL 878 L20. doi:10.3847/2041-8213/ab2538

Uranus ring

This remarkable image of Uranus, taken at 3.1 mm with the Atacama Large Millimeter/submillimeter Array (ALMA), reveals thermal emission from the dust that makes up Uranus’s narrow ring system (Uranus itself is masked because it’s so bright compared to the rings). We know that Uranus’s rings are made up of centimeter- to meter-sized particles, but little is known about the composition, mass, or the detailed size distribution of these particles or the amount dust in between them. In a new study led by Edward Molter (University of California, Berkeley), a team of scientists presents ALMA and Very Large Telescope observations of the rings’ thermal emission for the first time. These observations indicate that Uranus’s epsilon ring — the primary ring — is devoid of dust. This stands in stark contrast to the rings around Saturn or Jupiter, for instance, which contain lots of micrometer-sized dust — raising the question of why Uranus’s epsilon ring is so unusual! For more information, check out the article below.

Citation

“Thermal Emission from the Uranian Ring System,” Edward M. Molter et al 2019 AJ 158 47. doi:10.3847/1538-3881/ab258c

dwarf galaxy merger simulation

How do globular clusters — massive and dense gravitationally bound stellar systems — form? A team of scientists led by Natalia Lahén (University of Helsinki, Finland) explores the possibility that the mergers of gas-rich dwarf galaxies can result in the formation of massive, low-metallicity clusters of stars much like the local globular clusters we observe today. The beautiful series of images above are frames from the authors’ hydrodynamical simulations of the aftermath of a dwarf-galaxy merger. The three sets of panels show surface density of stars (left) and gas (center), and the thermal gas pressure (right), at two times during the simulation (the bottom panels are from 2 million years later than the top). The simulations demonstrate the formation of hundreds of stellar clusters in the filamentary gas structures after merger, including some with properties like local globular clusters. For more information, you can check out the article below.

Citation

“The Formation of Low-metallicity Globular Clusters in Dwarf Galaxy Mergers,” Natalia Lahén et al 2019 ApJL 879 L18. doi:10.3847/2041-8213/ab2a13

SMBH merger

What happens to accreting gas when two supermassive black holes merge? The dramatic scene above shows the behavior of disk gas in a still from a simulation of such a merger; the two smaller black disks represent the black holes, and the larger disk in the center is a cutout at the center of mass. In this new study, a team of scientists led by Dennis Bowen (Los Alamos National Laboratory and Rochester Institute of Technology) have conducted the first exploration of how magnetized mini-disks around supermassive black holes can couple to the accreting gas surrounding the binary in the moments shortly before the black holes merge. The team’s simulations show that asymmetries in this coupling can drive strong oscillations in the system — and these could introduce distinctive, increasingly rapid fluctuations in the electromagnetic emission that we might be able to detect from supermassive black hole mergers that are surrounded by gas. To learn more about the authors’ discoveries, check out the article below.

Citation

“Quasi-periodicity of Supermassive Binary Black Hole Accretion Approaching Merger,” Dennis B. Bowen et al 2019 ApJ 879 76. doi:10.3847/1538-4357/ab2453

PDS 70 system

The panels above show 10” x 14” images of dust emission from the disk that surrounds the young star PDS 70, captured with the Atacama Large Millimeter/submillimeter Array (ALMA). See that purple blob of emission on the inside-right of the disk in the center panel? According to a new study led by Andrea Isella (Rice University), that’s dust emission from what is likely a circumplanetary disk — a disk of gas and dust surrounding the newly forming giant planet PDS 70c, feeding its growth and possibly providing the material that will later form into one or more moons around the planet.

The PDS 70 system made headlines last year when its first planet, PDS 70b, was directly imaged (you can see it best in the background VLT/SPHERE image in the right panel).

In the grand scheme of a giant planet’s lifetime, the period of time when it is still surrounded by a circumplanetary disk is short, so PDS 70 system is one of the few instances where we’ve managed to capture this moment. By studying PDS 70, we hope to learn more about how gas giants — like our own Jupiter or Saturn — and their moon systems form. To learn more, check out the article below.

Citation

“Detection of Continuum Submillimeter Emission Associated with Candidate Protoplanets,” Andrea Isella et al 2019 ApJL 879 L25. doi:10.3847/2041-8213/ab2a12

T 37 cluster

This 53’-wide, false-color infrared image reveals the field containing the star cluster Trumpler 37, located ~3,000 light-years away. Here, T 37 can be seen near the head of IC 1396A, the colorful, bright-rimmed globule near the center of the image. In a recent study led by Huan Meng (Steward Observatory, University of Arizona), a team of scientists has used observations from the United Kingdom Infrared Telescope (UKIRT) spanning two full years to study the variability of stars in this young stellar cluster. The length of their study allowed them to identify 119 members of the cluster — discovering even low-mass members down to brown-dwarf size. By studying the stars in this cluster, Meng and collaborators hope to better understand what different factors drive young stellar objects like these to vary in emission — could it be changing accretion rates? Magnetic activity? Flares? Starspots? The effects of circumstellar disks? To find out what the authors learned, you can check out the article below.

Citation

“Near-infrared Variability of Low-mass Stars in IC 1396A and Tr 37,” Huan Y. A. Meng et al 2019 ApJ 878 7. doi:10.3847/1538-4357/ab1b14

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