Images of the companion object (circled) taken over the course of a year. The companion object is detected with a signal-to-noise ratio ranging from 10 to 19. Click to enlarge. [Kuzuhara et al. 2022]
“Direct-imaging Discovery and Dynamical Mass of a Substellar Companion Orbiting an Accelerating Hyades Sun-like Star with SCExAO/CHARIS,” Masayuki Kuzuhara et al 2022 ApJL 934 L18. doi:10.3847/2041-8213/ac772f
In June 2012, the Sun released a powerful solar flare and an explosive burst of plasma and magnetic fields called a coronal mass ejection. Days later, this solar storm swept through the inner solar system, where multiple spacecraft sampled the passing plasma and magnetic fields. In a recent publication, a team led by Qiang Hu (University of Alabama in Huntsville) used a new quasi-three-dimensional fitting method to analyze spacecraft data of the event and deduce the structure of the passing bundle of magnetic field lines. The image above shows the simulated strength and direction — with yellow being strong and outward pointing and blue being strong and inward pointing — of the magnetic field lines that the Wind spacecraft crossed as the storm traveled past it. (In this image, the spacecraft would be located roughly halfway along the length of the field lines.) These simulations show three-dimensional winding behavior, highlighted by the red lines in the image above, that was not present in one- or two-dimensional models of the same event. To learn more about this event and the authors’ new modeling technique, be sure to check out the full article below!
“Validation and Interpretation of a Three-dimensional Configuration of a Magnetic Cloud Flux Rope,” Qiang Hu et al 2022 ApJ 934 50. doi:10.3847/1538-4357/ac7803
Even though the Andromeda Galaxy is among our nearest galactic neighbors, there’s still much about it that we don’t know. Since the 1950s, astronomers have debated whether Andromeda, similar to the Milky Way, hosts a central bar of stars. Discerning Andromeda’s structure is key to understanding how it formed and evolved, but its tilted orientation makes it difficult to do so from our vantage point. Now, a team led by Zi-Xuan Feng (Shanghai Astronomical Observatory and University of the Chinese Academy of Sciences) has presented new evidence that shows Andromeda is indeed a barred galaxy. The above image shows the new results superimposed atop observations from the Hubble Space Telescope and the Subaru and Mayall ground-based telescopes. The red and blue symbols indicate the locations of velocity jumps — shocks — identified in emission from oxygen and hydrogen gas. Using simulations, Feng and collaborators show that shocks of this type cannot form without a rotating bar of stars. To learn more about the observations and simulations that led to this conclusion, be sure to check out the full article below!
“Large-scale Hydrodynamical Shocks as the Smoking-gun Evidence for a Bar in M31,” Zi-Xuan Feng et al 2022 ApJ 933 233. doi:10.3847/1538-4357/ac7964
The 12 galaxies in the sample, ordered from high to low stellar mass. Click for high-resolution version. [Gilhuly et al. 2022]
“Stellar Halos from the Dragonfly Edge-on Galaxies Survey,” Colleen Gilhuly et al 2022 ApJ 932 44. doi:10.3847/1538-4357/ac6750
When galaxies clash, is star formation heightened or quenched? The Taffy galaxies (UGC 12914/5) provide an excellent setting to probe this question. These two galaxies, shown above in a representative-color optical image from the Sloan Digital Sky Survey, collided head on just 25–30 million years ago, resulting in a bridge of turbulent gas that stretches across the space between them. A team led by Philip Appleton (California Institute of Technology/Infrared Processing and Analysis Center) carried out new Atacama Large Millimeter/submillimeter Array (ALMA) observations, the locations of which are marked with red circles in the image above, to study this interacting pair of galaxies. The team’s observations of carbon monoxide gas suggest that the filaments and clumps within the bridge that connects the two galaxies are likely gravitationally unbound. Without a source of pressure to keep them together, these potentially star-forming features are likely to dissipate within 2–5 million years. Despite this, star formation presses on in isolated regions. To learn more about the results of this galactic interaction, be sure to check out the full article below!
“The CO Emission in the Taffy Galaxies (UGC 12914/15) at 60 pc Resolution. I. The Battle for Star Formation in the Turbulent Taffy Bridge,” P. N. Appleton et al 2022 ApJ 931 121. doi:10.3847/1538-4357/ac63b2
What do you see when you look at these images? Clouds? Islands? Legos? Think smaller: simulated dust particles! Modelers often approximate dust grains as spheres, but real dust grains likely come in a range of shapes. A new publication led by Jessica Arnold (Army Research Laboratory) explores the impact of dust shapes on models of debris disks around young stars. Irregularly shaped dust grains, like those shown above, have been used to reproduce spectra of dust grains in a lab setting as well as those of dusty comets, making them a promising tool for modelers. Arnold and collaborators modeled dust grains three ways — as solid spheres, porous spheres, and randomly generated irregular shapes — to constrain the properties of the debris disk surrounding AU Microscopii. The three shapes yielded different best-fitting dust grain size distributions for AU Microscopii’s disk, suggesting that future modeling should account for the uncertainties introduced by grain shapes. To learn more about how astronomers decipher distant dust, be sure to read the full article below!
“Stumbling over Planetary Building Blocks: AU Microscopii as an Example of the Challenge of Retrieving Debris-disk Dust Properties,” Jessica A. Arnold et al 2022 ApJ 930 123. doi:10.3847/1538-4357/ac63a9
Though it’s not uncommon for stars to snack on their stellar companions from time to time, it’s rare for them to eat their associates entirely. This is the scenario proposed for black widow pulsars — tiny, dense stellar remnants that rotate rapidly, produce beams of radio emission and fierce winds, and, like the spiders from which they get their name, eventually consume their companions. Black widow pulsars may be the missing link in the creation of single millisecond pulsars — those that rotate hundreds to thousands of times a second but lack a neighboring star to lend them the angular momentum to do so. In a new article, a team led by Roger Romani (Stanford University) used images and spectra to study the first known black widow pulsar, PSR J1959+2048. The image above (click for the full view) reveals the shock created by the pulsar’s outflowing wind colliding with interstellar material. Romani and collaborators used this rare sight — there are only nine known pulsar wind nebulae with associated shocks — to begin the investigation into whether this pulsar will lose too much energy to fully consume its companion. To learn more about this unusual object, check out the full article below!
“The Bow Shock and Kinematics of PSR J1959+2048,” Roger W. Romani et al 2022 ApJ 930 101. doi:10.3847/1538-4357/ac6263
New radio observations from uGMRT (red) highlight the detailed structure of the radio relic that curves around the diffuse X-ray emission seen by the Chandra X-ray Observatory (blue). Various regions of the radio relic are labeled. Click for high-resolution version. [Rajpurohit et al. 2022]
“Deep Low-frequency Radio Observations of A2256. I. The Filamentary Radio Relic,” K. Rajpurohit et al 2022 ApJ 927 80. doi:10.3847/1538-4357/ac4708
Composite-color images of 20 of the galaxy clusters from the study. The contour lines show levels of mass density (white), magnification (cyan), and distance from the brightest galaxy in the cluster (green). Click for the high-resolution version. [Fox et al. 2022]
“The Strongest Cluster Lenses: An Analysis of the Relation between Strong Gravitational Lensing Strength and the Physical Properties of Galaxy Clusters,” Carter Fox et al 2022 ApJ 928 87. doi:10.3847/1538-4357/ac5024
Left: XMM-Newton X-ray observations (blue) overlaid on optical observations (red and green). Right: X-ray emission detected by the Chandra X-ray Observatory (blue) overlaid on the same optical image. Click to enlarge. [Toalá et al. 2022]
“An XMM-Newton EPIC X-Ray View of the Symbiotic Star R Aquarii,” Jesús A. Toalá et al 2022 ApJL 927 L20. doi:10.3847/2041-8213/ac589d