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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

Ho II X-1

This complex composite image reveals Holmberg II X-1, an example of an ultraluminous X-ray source (ULX). As the name suggests, ULXs are objects that shine anomalously bright in X-rays; they’re not as bright as active galactic nuclei, but they’re brighter than any known isotropic stellar process. What powers these unusual sources? Led by Ryan Lau (Japan Aerospace Exploration Agency and California Institute of Technology), a team of scientists is searching for more details by studying ULXs in a different wavelength: infrared. The false-color image above shows what the ULX Ho II X-1 looks like in combined Spitzer/IRAC 4.5 μm (red), HST/WFC Hα (green), HST/WFC V-band (blue) wavelengths. The source and its nebula — roughly 60 light-years across — are contained within the white box. Lau and collaborators’ search for infrared counterparts to nearly 100 ULXs show that some ULXs are redder in infrared than others, which the authors propose is a consequence of thermal emission from circumstellar or circumbinary dust. To learn more about we’ve discovered about these odd sources, check out the article below.

Citation

“Uncovering Red and Dusty Ultraluminous X-Ray Sources with Spitzer,” Ryan M. Lau et al 2019 ApJ 878 71. doi:10.3847/1538-4357/ab1b1c

pre-planetary nebulae

This collection of ten spectacular Hubble images (click for a closer look) reveals what are known as pre-planetary nebulae: glowing clouds of gas formed shortly after a star reaches the end of the asymptotic giant branch (AGB) evolutionary phase. During a star’s AGB phase, gas flows off of the star in the form of slow winds, filling the environment around it. After the end of the star’s AGB lifetime, it can emit jets that punch through the winds — shaping the surrounding gas into the hollow, candle-flame-shaped lobes seen in these images. In a recent study led by Bruce Balick (University of Washington, Seattle), a team of scientists has used models to explore the formation histories of these candle-like pre-planetary nebulae. To learn more about the team’s work, check out the article below.

Citation

“Models of the Mass-ejection Histories of Pre-planetary Nebulae. III. The Shaping of Lobes by Post-AGB Winds,” Bruce Balick et al 2019 ApJ 877 30. doi:10.3847/1538-4357/ab16f5

SNR CTB 1

In the dramatic false-color radio images above, captured by the Canadian Galactic Plane Survey (background) and the Very Large Array (zoomed-in inset), a pulsar — a rapidly spinning, magnetized neutron star — is seen plunging out of a supernova remnant and taking off into interstellar space. The green cross marks the center of the supernova remnant CTB 1, and the green circle marks the location of the pulsar PSR J0002+6216. The tail of radio-emitting gas extending behind the pulsar toward the nebula is a dead giveaway to this object’s origin: the pulsar was likely born from the very same supernova explosion that produced the remnant. Supernova explosions don’t have perfect symmetry, and the pulsar likely received a natal kick that sent it tearing away from its birthplace at tremendous speeds, causing it to eventually overtake the expanding shell of gas and dust. In a recent study led by Frank Schinzel (National Radio Astronomy Observatory), a team of scientists presents and discusses the evidence that this runaway pulsar came from CTB 1. To read more, check out the article below.

Citation

“The Tail of PSR J0002+6216 and the Supernova Remnant CTB 1,” F. K. Schinzel et al 2019 ApJL 876 L17. doi:10.3847/2041-8213/ab18f7

solar cavity eruption

The dramatic image above reveals the expansion of a large coronal cavity as it erupts from the Sun’s surface in the form of a coronal mass ejection. This is a combination of LASCO (background) and SWAP (overlay) observations; click to see the larger field, which spans 3 x 5 solar radii (the white quarter-circle marks one solar radius). To better understand what triggers powerful solar ejections, a team of scientists led by Ranadeep Sarkar (Udaipur Solar Observatory, India) has pieced together observations over time of a coronal cavity that was witnessed in 2010. This low-density cavity formed above the Sun’s surface and hung peacefully in the lower corona for nearly two weeks before erupting violently in a surge of plasma and radiation.

coronal cavity

This image of the cavity was taken with SDO nearly two weeks before the LASCO/SWAP image above. Here, the cavity is much smaller and sits in the lower corona above a prominence. [Adapted from Sarkar et al. 2019]

Sarkar and collaborators used observations from multiple vantage points — from the SDO, STEREO, SWAP, and LASCO observatories — to track the cavity’s evolution from a quiet bubble in the lower corona (see image to the right) to eruption into space. To see more images of the cavity and find out more about what the authors learned, check out the article below.

Citation

“Evolution of the Coronal Cavity From the Quiescent to Eruptive Phase Associated with Coronal Mass Ejection,” Ranadeep Sarkar et al 2019 ApJ 875 101. doi:10.3847/1538-4357/ab11c5

NGC 6946

NGC 6946 SNRs

Supernova remnants in the spiral galaxy NGC 6946. Field is the same as that shown in the full image above. [Long et al. 2019]

The face-on spiral galaxy NGC 6946 is revealed in the stunning false-color image above (click for the full view), constructed from observations of three emission lines with the WIYN telescope at Kitt Peak Observatory. NGC 6946 is undergoing a major starburst, earning it the moniker “the Fireworks Galaxy”; evidence of its star-forming activity can be seen in the 10 supernovae (labeled in yellow) that have been observed within it since 1917. In a recent study led by Knox Long (Space Telescope Science Institute and Eureka Scientific, Inc.), scientists have undertaken a new optical search of NGC 6946 for supernova remnants — the ghostly remains of past stellar explosions. The resulting data to the right shows that NGC 6946 is positively rich with supernova remnants; green circles indicate remnant candidates found in a previous study, and blue circles indicate new remnant candidates discovered in optical in the current study. Red markers indicate objects for which the authors obtained spectra, reported in this study. To learn more, check out the article below.

Citation

“A New, Larger Sample of Supernova Remnants in NGC 6946,” Knox S. Long et al 2019 ApJ 875 85. doi:10.3847/1538-4357/ab0d94

Cosmic Horseshoe

These beautiful images reveal the Cosmic Horseshoe, a gravitational lens system, in a 20-square-arcsecond field in five different Hubble filter bands. The lovely arc — a nearly complete Einstein ring — is created by the strong gravitational lensing of a background source (or sources) by a foreground object. In this case, the foreground object is a luminous red galaxy, visible as the bright source in the center of the ring. But what is the background, lensed source? Complex modeling of the lens system is necessary to disentangle the observations and reconstruct the source. A study led by Jun Cheng (Purdue University) uses a new method to fit different lens models to Hubble images of the Cosmic Horseshoe. While past models have focused on a scenario in which a single star-forming galaxy is lensed to form the Einstein ring, Cheng and collaborators show that there may be at least two background sources contributing to the total Einstein-ring flux of the Cosmic Horseshoe. For more information, check out the article below!

Citation

“Adaptive Grid Lens Modeling of the Cosmic Horseshoe Using Hubble Space Telescope Imaging,” Jun Cheng et al 2019 ApJ 872 185. doi:10.3847/1538-4357/ab0029

TOAST projection

This unique way of looking at the sky (click for the full view) shows an octahedron-based projection of the 408 MHz all-sky map. Map projections are how we represent a spherical surface like the sky on flat surfaces like sheets of paper and computer monitors. Different projections are designed to meet different goals — and because astronomers use many different projections, large data sets should ideally be stored in a way that can easily be converted to the projection of choice. The Tessellated Octahedral Adaptive Spherical Transformation (TOAST) Projection, demonstrated above, is used by projects like the WorldWide Telescope to store data. In a recent study, a team of scientists led by Thomas McGlynn (NASA Goddard SFC) proposes that octahedron-based projections like this one make for an ideal intermediate representation; from this, it’s easy to convert the data to whatever projection is requested by the user. For a closer look at the fascinating math acrobatics behind projections — and for more awesome images of what those projections look like — check out the article below.

Citation

“Octahedron-based Projections as Intermediate Representations for Computer Imaging: TOAST, TEA, and More,” Thomas McGlynn et al 2019 ApJS 240 22. doi:10.3847/1538-4365/aaf79e

W51A

The image above (click for the full view) is a false-color, three-wavelength infrared look at an enormous ionized cloud in which new, large stars are just beginning to form. When young, massive stars are first born within a cloud of gas and dust, they eventually become hot enough to ionize a bubble of gas around them. When stars form near each other, as in a massive cluster, the individual bubbles can combine, producing large ionized regions known as giant H II regions. In a new survey, scientists are using the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) to map out all of the Milky Way giant H II regions in the mid-infrared, in order to better understand the earliest stages of massive and clustered star formation. W51A, shown above in two FORCAST wavelengths (20 µm shown in blue, 37 µm in green) and one Herschel (70 µm, shown in red), is one of the largest and brightest giant H II regions in our galaxy, and one of the first regions observed as part of the survey. A recent publication by SOFIA scientists Wanggi Lim and James De Buizer details what we’ve learned so far; check out the article below for more information, and keep an eye on AAS Nova for more on SOFIA science soon!

Citation

“Surveying the Giant H ii Regions of the Milky Way with SOFIA. I. W51A,” Wanggi Lim and James M. De Buizer 2019 ApJ 873 51. doi:10.3847/1538-4357/ab0288

galaxy gas simulations

These beautiful images (click for the full view) from a simulation of a Milky-Way-sized, isolated disk galaxy capture how the presence of gas affects a galaxy’s formation and evolution over time. The simulations, run by a team of scientists led by Woo-Young Seo (Seoul National University and Chungbuk National University, Republic of Korea), demonstrate that the amount of gas present in a forming galaxy influences the formation of features like spiral structure, a central bar, and even a nuclear ring — a site of intense star formation that encircles the very center of the galaxy. The images above (sized at 20 x 20 kpc) and below (same simulation, but zoomed to the central 2 x 2 kpc region) follow a warm galaxy model with a 5% gas fraction over the span of 5 billion years. For more information about the authors’ discoveries — and more gorgeous images of simulated, evolving galaxies — check out the article linked below.

galaxy gas simulations zoom

Citation

“Effects of Gas on Formation and Evolution of Stellar Bars and Nuclear Rings in Disk Galaxies,” Woo-Young Seo et al 2019 ApJ 872 5. doi:10.3847/1538-4357/aafc5f

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