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twin jets in close binaries

The stills above (click for the full view!) represent different time stages in the formation of a close stellar binary from a collapsing cloud of gas. In a recent study, two researchers from Kyushu University in Japan, Yu Saiki and Masahiro Machida, conduct numerical simulations to track the complicated process of a binary’s formation and evolution over ~400 years. In the above frames, the top left panel shows the fragmentation of the gas cloud into two cores roughly 9,000 years after the cloud initially begins to collapse. The succeeding panels show how the separation between these two protostars shrinks over the next several hundred years and disks of gas form around each star and around the binary pair. Saiki and Machida’s simulations also show the high-velocity jets driven from each protostar in the process (see the video below), and how the twin jets tangle on large scales as the stars orbit one another. The characteristics revealed in these simulations neatly reproduce our observations of protobinary systems. For more information, check out the original article linked below the video.

Citation

“Twin Jets and Close Binary Formation,” Yu Saiki and Masahiro N. Machida 2020 ApJL 897 L22. doi:10.3847/2041-8213/ab9d86

dusty ring evolution

These stills from a 2D hydrodynamic simulation show how a ring of dust and gas surrounding a newly born star might behave as it evolves. The frames illustrate the dust-to-gas ratio after 260 (left), 600 (center), and 1,740 (right) orbits of the dusty ring around the star. These simulations were conducted as part of a study led by Pinghui Huang (Chinese Academy of Sciences and Tsinghua University, China; Los Alamos National Laboratory; Rice University). The results demonstrate how such a ring can become unstable at its edges, forming small vortices that develop into many clumps of dust. Each of these clumps contains at least 10% of Earth’s mass, potentially forming the seeds from which baby planets can grow in the environment around the young star. For more information on the authors’ results, check out the original article below.

Citation

“Meso-scale Instability Triggered by Dust Feedback in Dusty Rings: Origin and Observational Implications,” Pinghui Huang et al 2020 ApJ 893 89. doi:10.3847/1538-4357/ab8199

eclipse composite

This stunning image of the Sun and its corona (click for a closer look) is composited from hundreds of individual frames captured by Nicolas Lefaudeux at the Cerro Tololo Inter-American Observatory in Chile. The occasion: a team effort to image a total solar eclipse in July 2019.

In a recent Research Note led by Christian Lockwood (Williams College), you can read about how the team gathered images (like those composited above) using three different observatories in Chile during the eclipse. Lockwood and collaborators then combined these ground-based images — which had high resolution and a wide field of view — with close-in observations of the solar disk made by space-based satellites.

By putting these overlapping observations together, the team could paint a full picture of the Sun’s tenuous, extended outer atmosphere during solar minimum. To learn more about the project, check out the article below.

Citation

“Compositing Eclipse Images from the Ground and from Space,” Christian A. Lockwood et al 2020 Res. Notes AAS 4 133. doi:10.3847/2515-5172/abacb5

basalt oxidization

Is Venus still volcanically active today? A new study led by Kyra Cutler (USRA’s Lunar and Planetary Institute; University of Birmingham, UK) investigated this question in an unusual way: by examining how rocks age in a laboratory. The photo above shows a sample of alkali basalt before and after it was exposed to 7 weeks of oxidization in a furnace to reproduce conditions similar to those on Venus’s surface. The mineralogical changes of the rock can be easily seen here — particularly the formation of hematite, visible as small white specks — and it’s even more dramatically evident in the reflectance spectra captured to mimic remote observations of Venus. Cutler and collaborators’ experiments indicate that if the basalt on the surface of Venus contains olivine or glass, some lava flows we’ve observed can only be a few years old. And even in the unlikely event that the basalt is fully crystalline instead, it’s still at most decades to hundreds of years old. These results strongly indicate that Venus is currently volcanically active. To learn more about the authors’ work, check out the article below.

Citation

“Experimental Investigation of Oxidation of Pyroxene and Basalt: Implications for Spectroscopic Analyses of the Surface of Venus and the Ages of Lava Flows,” K. S. Cutler et al 2020 Planet. Sci. J. 1 21. doi:10.3847/PSJ/ab8faf

hollow ice sphere

You’re looking at a frozen, hollow shell of ice roughly 20 cm in diameter and 3 cm thick. In a new laboratory study, scientists Kathryn Harriss and Mark Burchell (University of Kent, UK) have studied what happens when a shell like this is shot with a small, high-speed projectile, causing the ice shell to explode into pieces. You can watch a slow motion video of their experiment below!

This process simulates the possible high-speed collisions and catastrophic disruptions of icy bodies — like the frozen moons of Saturn and Jupiter — in the early solar system. By exploring how a hollow ice sphere responds to impact, Harriss and Burchell hope to better understand the relative roles of a body’s core and its surface layers in determining what happens during a catastrophic disruption. Which is more important in a collision: an icy object’s crust or its core? Check out the original article, linked below, for more information on what the authors learned.

Citation

“Catastrophic Disruption of Hollow Ice Spheres,” Kathryn H. Harriss and Mark J. Burchell 2020 Planet. Sci. J. 1 19. doi:10.3847/PSJ/ab8f34

atmospheric ion loss

Could TOI-700 d, an Earth-sized planet in the habitable zone of an early-type M-dwarf star, have held on to its atmosphere over long timescales? This question is crucial to understanding whether this recent discovery from the Transiting Exoplanet Survey Satellite (TESS) is likely to have a habitable surface. In a recent study led by Chuanfei Dong (Princeton University), a team of scientists conducted a series of state-of-the-art simulations to model the atmospheric escape from TOI-700 d as the planet is bombarded by its host’s stellar wind. The plots above show the O+ ion density and magnetic field lines in various cases from the authors’ simulations (see the original image for scales and additional detail). Though TOI-700 d’s atmospheric ion escape rates could be a few orders of magnitude higher than the rates typical of the terrestrial planets in our own solar system, the authors show that TOI-700 d could still retain a substantial atmosphere for more than a billion years — so it may well be worth exploring this planet further in the future! For more information, check out the full article below.

Citation

“Atmospheric Escape From TOI-700 d: Venus versus Earth Analogs,” Chuanfei Dong et al 2020 ApJL 896 L24. doi:10.3847/2041-8213/ab982f

Betelgeuse binary merger

This image from a simulation shows how the the large, red supergiant star Betelgeuse may have been created by the tidal disruption and merger of a binary star within the past few hundred thousand years. Betelgeuse — a prominent star in our night sky — has recently made headlines due to its unexpected, sudden dimming and rebrightening. But the supergiant has other quirks, like how it’s hurtling rapidly through space as a “runaway” star, or how it spins unusually fast for its size. A team of Louisiana State University researchers led by Manos Chatzopoulos has now performed simulations that show that Betelgeuse’s odd properties could be explained if the supergiant was formed by the merger of an unequal-mass binary star system in the relatively recent past. To learn more about the authors’ results, check out the original article below.

Betelgeuse merger full

The full view of two frames from one of the authors’ simulations. The left image shows the original configuration of the unequal-mass binary star system; the right image shows the tidal disruption of the secondary around the core of the primary. [Chatzopoulos et al. 2020]

Citation

“Is Betelgeuse the Outcome of a Past Merger?,” E. Chatzopoulos et al 2020 ApJ 896 50. doi:10.3847/2041-8205/820/2/L40

turbulent mixing layer simulation

What happens in galactic and intergalactic settings when cold, dense gas moves through hot, diffuse gas? You can see the result in the complex simulations shown above (click for a closer look), as reported in a recent publication led by scientist Drummond Fielding (Center for Computational Astrophysics, Flatiron Institute). Turbulent mixing layers like those simulated by Fielding and collaborators form in a vast variety of cosmic environments: the interstellar medium, the circumgalactic medium, expanding supernova remnants, cosmic filaments, galactic winds, protoplanetary disks, the solar corona, and many more. The authors’ new models show the fractal nature of the cooling surface that arises within these layers as the gases mix.

You can watch the animated version of the simulation below, which shows how eight different fluid properties evolve over time in a turbulent layer containing mixing cold and hot gas. For more information, check out the original article, linked below.

Citation

“Multiphase Gas and the Fractal Nature of Radiative Turbulent Mixing Layers,” Drummond B. Fielding et al 2020 ApJL 894 L24. doi:10.3847/2041-8213/ab8d2c

BUFFALO image of A370

Be sure to click on the above image and enlarge it for the full view of the stunning, rich galaxy cluster Abell 370 (top right) and its surrounding area. This image was captured as part of the Beyond Ultra-deep Frontier Fields and Legacy Observations (BUFFALO) program, which is using 101 orbits of Hubble Space Telescope time to revisit the six Hubble Frontier Fields galaxy clusters and their flanking regions. Expanding on the Frontier Fields study, each set of BUFFALO images covers a region that’s four times larger than the previous coverage — the red-shaded section above shows the area that was previously imaged through Frontier Fields. BUFFALO’s wide, deep look will take advantage of gravitational lensing from these massive galaxy clusters to do two things: discover distant, high-redshift galaxies that lie behind the clusters, and study dark matter and galaxy assembly using the foreground clusters. For more information, check out the below article led by Charles L. Steinhardt (Cosmic Dawn Center (DAWN) and University of Copenhagen) that describes the study.

Citation

“The BUFFALO HST Survey,” Charles L. Steinhardt et al 2020 ApJS 247 64. doi:10.3847/1538-4365/ab75ed

MCPM cosmic web reconstruction

The image above and its zoomed-in insets show a reconstruction of the cosmic web — a vast network of filamentary structures of matter spanning the universe. Simulations indicate that the universe’s matter should be organized into these complex threads, but this model has proven difficult to test observationally; most of the material is invisible dark matter, and the remainder is diffuse and distant, making it challenging to detect. A team of scientists led by Joseph Burchett (UC Santa Cruz) has now taken an unusual approach to modeling the cosmic web: they use the growth patterns of slime mold as a foundation. Slime mold has been shown to be very efficient when forming networks between sources of food — and when Burchett and collaborators model slime-mold-like networks forming between a sample of nearly 38,000 galaxies (the “food”) observed with the Sloan Digital Sky Survey, the model produces a web of filaments that well matches simulations of the cosmic web. The team further tests their model against Hubble observations of intergalactic medium (IGM) density, finding that the bulk of the IGM is, indeed, concentrated along cosmic web filaments traced by the slime mold model. To read more about this unusual study, check out the article below.

Citation

“Revealing the Dark Threads of the Cosmic Web,” Joseph N. Burchett et al 2020 ApJL 891 L35. doi:10.3847/2041-8213/ab700c

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