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This remarkable false-color, mid-infrared image (click for the full view!) was produced by the Wide-field Infrared Survey Explorer (WISE). It captures a tantalizing view of Sh 2-207 and Sh 2-208, the latter of which is one of the lowest-metallicity star-forming regions in the Galaxy. In a recent study led by Chikako Yasui (University of Tokyo and the Koyama Astronomical Observatory), a team of scientists has examined this region to better understand how star formation in low-metallicity environments differs from that in the solar neighborhood. The authors’ analysis suggests that sequential star formation is taking place in these low-metallicity regions, triggered by an expanding bubble (the large dashed oval indicated in the image) with a ~30 pc radius. You can find out more about their study by checking out the paper below!

Citation

Chikako Yasui et al 2016 AJ 151 115. doi:10.3847/0004-6256/151/5/115

RT turbulence

This image shows a computer simulation of the hydrodynamics within a supernova remnant. The mixing between the outer layers (where color represents the log of density) is caused by turbulence from the Rayleigh-Taylor instability, an effect that arises when the expanding core gas of the supernova is accelerated into denser shell gas. The past standard for supernova-evolution simulations was to perform them in one dimension and then, in post-processing, manually smooth out regions that undergo Rayleigh-Taylor turbulence (an intrinsically multidimensional effect). But in a recent study, Paul Duffell (University of California, Berkeley) has explored how a 1D model could be used to reproduce the multidimensional dynamics that occur in turbulence from this instability. For more information, check out the paper below!

Citation

Paul C. Duffell 2016 ApJ 821 76. doi:10.3847/0004-637X/821/2/76

TW Hya

This remarkable image (click for the full view!) is a high-resolution map of the 870 µm light emitted by the protoplanetary disk surrounding the young solar analog TW Hydrae. A recent study led by Sean Andrews (Harvard-Smithsonian Center for Astrophysics) presents these observations, obtained with the long-baseline configuration of the Atacama Large Millimeter/submillimeter Array (ALMA) at an unprecedented spatial resolution of ~1 AU. The data represent the distribution of millimeter-sized dust grains in this disk, revealing a beautiful concentric ring structure out to a radial distance of 60 AU from the host star. The apparent gaps in the disk could have any of three origins:

  1. Chemical: apparent gaps can be caused by condensation fronts of volatiles
  2. Magnetic: apparent gaps can be caused by radial magnetic pressure variations
  3. Dynamic: actual gaps can be caused by the clearing of dust by young planets.

For more information, check out the paper below!

Citation

Sean M. Andrews et al 2016 ApJ 820 L40. doi:10.3847/2041-8205/820/2/L40

Toothbrush Cluster

This stunning composite image shows the components of the galaxy cluster RX J0603.3+4214, located at a redshift of z=0.225. This image contains Chandra X-ray data (red), radio data from the Giant Metrewave Radio Telescope (green), and optical from the Subaru Telescope (background). The shape of the enormous (6.5 million light-years across!) radio relic, shown in green, gives this collection of galaxies its nickname: the “Toothbrush Cluster.”  A team of scientists led by Myungkook James Jee (Yonsei University and University of California, Davis) used Hubble and Subaru to study weak gravitational lensing by the Toothbrush Cluster, in order to determine how the cluster’s mass is distributed. Jee and collaborators found that most of the dark-matter mass is located in two large clumps on a north-south axis (shown by the white contours overlaid on the image), suggesting that the Toothbrush Cluster is the result of a past merger between two clusters. This violent merger is likely what caused the enormous “Toothbrush” radio relic. Check out the paper below for more information!

Citation

M. James Jee et al 2016 ApJ 817 179. doi:10.3847/0004-637X/817/2/179

common envelope simulation

This beautiful series of snapshots from a simulation (click for a better look!) shows what happens when two stars in a binary system become enclosed in the same stellar envelope. In this binary system, one of the stars has exhausted its hydrogen fuel and become a red giant, complete with an expanding stellar envelope composed of hydrogen and helium. Eventually, the envelope expands so much that the companion star falls into it, where it releases gravitational potential energy into the common envelope. A team led by Sebastian Ohlmann (Heidelberg Institute for Theoretical Studies and University of Würzburg) recently performed hydrodynamic simulations of this process. Ohlmann and collaborators discovered that the energy release eventually triggers large-scale flow instabilities, which leads to turbulence within the envelope. This process has important consequences for how these systems next evolve (for instance, determining whether or not a supernova occurs!). You can check out the authors’ video of their simulated stellar inspiral below, or see their paper for more images and results from their study.

Citation

Sebastian T. Ohlmann et al 2016 ApJ 816 L9. doi:10.3847/2041-8205/816/1/L9

SDO AIA prominences

STEREO prominenceIn these images from the Solar Dynamics Observatory’s AIA instrument (click for the full resolution!), two solar prominence eruptions (one from June 2011 and one from August 2012) are shown in pre- and post-eruption states. The images at the top are taken in the Fe XII λ193 bandpass and the images at the bottom are taken in the He II λ304 bandpass. When a team of scientists searched through seven years of solar images taken by the STEREO (Solar Terrestrial Relations Observatory) spacecraft, these two eruptions were found to extend all the way out to a distance of 1 AU. They were the only two examples of clear, bright, and compact prominence eruptions found to do so. The scientists, led by Brian Wood (Naval Research Laboratory), used these observations to reconstruct the motion of the eruption and model how prominences expand as they travel away from the Sun. The image to the right shows a STEREO observation compared to the team’s 3D model of the prominence’s shape and expansion. To learn more about the results from this study, check out the paper below.

Citation

Brian E. Wood et al 2016 ApJ 816 67. doi:10.3847/0004-637X/816/2/67

Malin 1

Malin 1 inverted

Monochrome, inverted version of Malin 1. [Adapted from Galaz et al. 2015]

The above image of Malin 1, the faintest and largest low-surface-brightness galaxy ever observed, was obtained with an instrument called Megacam on the 6.5m Magellan/Clay telescope. Gaspar Galaz (Pontifical Catholic University of Chile) and collaborators used Megacam to obtain deep optical observations of Malin 1. They then used novel noise-reduction and image-processing techniques to create this spectacular image of the spiral galaxy — located roughly 1.2 billion light-years away. This new view of Malin 1 reveals details we’ve never before seen, including a stream within the disk that may have been caused by a past interaction between Malin 1 and another galaxy near it. Check out the image to the right for a monochrome, inverted version that makes it a little easier to see some of Malin 1’s features. To see the full original images and to learn more about what the images reveal about Malin 1, see the paper below.

Citation

Gaspar Galaz et al 2015 ApJ 815 L29. doi:10.1088/2041-8205/815/2/L29

M31 UV

As distant light travels on a path toward us, it can be absorbed by intervening, interstellar dust. Much work has been done to understand this “dust extinction” in the Milky Way, providing us with detailed information about the properties of the dust in our galaxy. Far less, however, is known about the dust extinction of other galaxies. The image above, taken with the ultraviolet space telescope GALEX, identifies the locations of four stars in the nearby Andromeda galaxy (click for a full view!) that are reddened due to extinction of their light by dust within Andromeda. In a recent study led by Geoffrey Clayton (Louisiana State University), new, high-signal-to-noise spectra were obtained for these four stars using Hubble’s Space Telescope Imaging Spectrograph. These observations have allowed the authors to construct dust extinction curves to carefully study the nature of Andromeda’s interstellar dust. To learn about the results, see the paper below.

Citation

Geoffrey C. Clayton et al 2015 ApJ 815 14. doi:10.1088/0004-637X/815/1/14

S4G galaxies

These three galaxies (click for a full view!) were imaged as a part of the Spitzer Survey of Stellar Structure in Galaxies (S4G), a recent survey of 2352 nearby galaxies with deep imaging at 3.6 and 4.5 μm. The bottom panels show false-color near-UV and far-UV images previously obtained with GALEX. The top panels show the new images obtained with Spitzer as part of S4G. The three galaxies shown here represent three types of galaxies that have a high concentration of mass in their centers, yet still have a high specific star-formation rate (the star formation rate per unit stellar mass):

  1. Barred galaxies with a prominent ring around their nucleus, like NGC 7552
  2. Interacting systems, like NGC 2782
  3. Galaxies with compact bulges and smooth extended disks, like NGC 3642

To learn why this is the case, and to see more results from S4G, see the original paper below.

Citation

Juan Carlos Muñoz-Mateos et al 2015 ApJS 219 3. doi:10.1088/0067-0049/219/1/3

Westerlund 2 Cluster

This is a color composite image from Hubble of the very young star cluster Westerlund 2, seen near the center of the image (click for the full view!). The image was produced using visible-light data from the Advanced Camera for Surveys and near-infrared data from the Wide Field Camera 3. A recently-published study, led by Peter Zeidler (Center for Astronomy at Heidelberg University), reports the results of a high-resolution multi-band survey of the Westerlund 2 region with Hubble. In their detailed analysis of the cluster, the authors cataloged over 17,000 objects in six different filters! They find that the cluster actually consists of two separate clumps that were born at the same time but have different stellar densities. For more information and the original image, see the paper here:

Citation

Peter Zeidler et al 2015 AJ 150 78. doi:10.1088/0004-6256/150/3/78

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