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Direct image of a bright, blue swirl of material forming a spiral disk with long streamers.

You’re looking at a photograph of a swirling disk of gas and dust that surrounds a star more than 500 light-years away. This stunning image (click for the full view!) of SU Aurigae’s circumstellar disk was brought to you by the ESO Very Large Telescope’s SPHERE instrument, which is working to capture up-close looks at planetary birthplaces like this one as part of the DESTINYS program. The results for SU Aur are presented in a recent publication led by Christian Ginski (University of Amsterdam and Leiden Observatory, the Netherlands). Here, the disk of SU Aur is resolved down to scales of just ~7 au, showing the extended dust structures around the young star in unprecedented detail. The image reveals the spiral structure of the disk and a shadow lane cast by an inner, misaligned disk component. These observations provide evidence that accretion can shape the disks around stars even in later stages of a star’s formation, possibly leading to planetary systems that have their spins and orbits misaligned. For more information, check out the annotated image and the authors’ original article below.

annotated version of the cover image marks the shadowed region and tails of dust.

Annotated VLT/SPHERE image of SU Aur. [Ginski et al. 2021]

Citation

“Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Late Infall Causing Disk Misalignment and Dynamic Structures in SU Aur,” Christian Ginski et al 2021 ApJL 908 L25. doi:10.3847/2041-8213/abdf57

Two plots, one with a wireframe model overlaid, show a white-light image of a coronal mass ejection erupting from the sun.

Learning about enormous solar explosions requires both observations that span the electromagnetic spectrum and careful modeling. The figure above shows a white-light image taken during a radio burst that was accompanied by a coronal mass ejection — a rapid release of plasma and radiation from the Sun’s outer atmosphere — in 2015. A new study led by Sherry Chhabra (New Jersey Institute of Technology and NASA Goddard SFC) presents long-wavelength radio images of this burst captured with the Owens Valley Radio Observatory. The team then uses the radio observations and white-light images from SOHO/LASCO to reconstruct the coronal mass ejection as it is released from the Sun; the model is shown above in the right panel as the green wireframe overlaid on the LASCO image (which is roughly 3° x 3°). The combined information about this burst tells us more about its properties and emission mechanisms, helping us to understand how energy is released from the Sun. For more information, check out the original article below.

8 panel plot showing 4 stages of eruption in both white light and radio light.

The different stages of eruption can be seen from left to right in these white-light (top) and radio (contours and bottom) images tracking the radio burst and associated CME. [Chhabra et al. 2020]

Citation

“Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA,” Sherry Chhabra et al 2021 ApJ 906 132. doi:10.3847/1538-4357/abc94b

ALMA image of two protostellar systems, one a triple with a disk and the other a wide companion.

How do systems of multiple stars form in the dense cores inside molecular clouds? Systems like the one captured above, L1448 IRS3B and A, may help us to better understand this process. In the image shown above (and again below, with scales and color bars), the triple protostar system IRS3B is seen in the process of forming from a surrounding (circum-triple) disk of molecular gas and dust. An additional disk can be seen at the opposite end of the image: IRS3A, a wide companion that lies 2,300 au away. In a recent study led by Nickalas Reynolds (University of Oklahoma), a team of scientists peered deep into the Perseus molecular cloud with the Atacama Large Millimeter/submillimeter Array (ALMA) to produce these images and study IRS3B and A. Reynolds and collaborators determine from their observations that the disk of IRS3B is gravitationally unstable at radii of 200–500 au, and its fragmentation may have recently produced the third protostar in IRS3B (visible as the outer bright spot in the circum-triple disk), which lies at 230 au. For more information, check out the full figure and the article below.

ALMA image of a triple star system with a wide companion, each surrounded by a disk.

Left: ALMA 879 μm continuum observation of L1448 IRS3B (bottom) and A (top). Right: zoomed-in view of each of the two sources. Both protostellar systems are surrounded by disks, and the images of IRS3B reveal three bright sources forming within the circum-triple disk. [Reynolds et al. 2021]

Citation

“Kinematic Analysis of a Protostellar Multiple System: Measuring the Protostar Masses and Assessing Gravitational Instability in the Disks of L1448 IRS3B and L1448 IRS3A,” Nickalas K. Reynolds et al 2021 ApJL 907 L10. doi:10.3847/2041-8213/abcc02

Oph 98AB

A new pair of free-floating planetary-mass objects has recently been identified via direct imaging: Oph 98 AB. In a study led by Clémence Fontanive (University of Bern, Switzerland), a team of scientists presents their observations of this set of two bodies locked in an exceptionally wide orbit. In the three views above (click for a closer look), captured at different times with different telescopes, you can see Oph 98 A and B as the two bright objects at the centers of the images. The additional source at the top right is a background star. Fontanive and collaborators show that this binary system consists of two bodies of perhaps 15 and 8 Jupiter masses, separated by around 200 au (for reference, Pluto’s semimajor axis is just 39 au!). The low masses and wide separation of Oph 98 AB make it the lowest binding energy system imaged to date, and it’s sure to offer us new insight into young, free-floating planetary-mass objects. To learn more, check out the original article below.

Citation

“A Wide Planetary-mass Companion to a Young Low-mass Brown Dwarf in Ophiuchus,” Clémence Fontanive et al 2020 ApJL 905 L14. doi:10.3847/2041-8213/abcaf8

star cluster locations

Did you know that the stars around us are organized into a tangle of threads and strings? The unprecedented precision and sensitivity of the Gaia second data release has given us the ability to map the precise locations of and distances to the stars around us, allowing us to piece together these clusters and structures. In a new study led by Marina Kounkel (Western Washington University), a team of scientists has conducted clustering analysis to identify a total of 8,292 structures of stars within about 10,000 light-years of us. These threads have a typical length of ~650 light-years and width of ~30 light-years, and they likely trace the shape of the filamentary giant molecular clouds from which they formed. The image above shows the 2D projection of the locations of some of these clustered stars, but to really dive into the data, you need to see it in 3D. For that, you can check out the authors’ interactive figure, which allows you to manipulate their data and view the strings from your angle of choice. We’ll be discussing interactive figures further on this site soon! In the meantime, you can check out the authors’ work (and their figures) in the article below.

Citation

“Untangling the Galaxy. II. Structure within 3 kpc,” Marina Kounkel et al 2020 AJ 160 279. doi:10.3847/1538-3881/abc0e6

neon microcrystal

Some astronomical mysteries are found deep in the interiors of stars. Such is the case with the puzzle of Q-branch white dwarfs, a population of these evolved, dense stars that seems to have an unexpected heat source, causing them to cool more slowly than a typical white dwarf. One hypothesis proposes that Q-branch white dwarfs gain extra heat from the rapid sedimentation — sinking to the center of the star — of neutron rich neon, 22Ne. But recent molecular dynamics simulations conducted by Matt Caplan (Illinois State U.), Charles Horowitz (Indiana U.), and Andrew Cumming (McGill U., Canada) show that the tiny crystals of neon needed to speed up this sedimentation can’t exist in a stable state in the interior of a typical white dwarf — which means there must be some other mechanism at work heating Q-branch white dwarfs. The image above shows the initial state of the authors’ simulations, in which a 22Ne microcrystal (red) lies within a soup of carbon and oxygen (white) under the dense, high-pressure conditions that exist inside a white dwarf. To read more about the authors’ work, check out the article below.

Citation

“Neon Cluster Formation and Phase Separation during White Dwarf Cooling,” M. E. Caplan et al 2020 ApJL 902 L44. doi:110.3847/2041-8213/abbda0

giant impact

The panels in the image above (click the cover image for the full view, or click the video below to watch the animated version) show frames from a dramatic simulation of the collision of a planetary-mass impactor with the proto-Earth in the early solar system. In the chaos that follows the collision, the debris that doesn’t escape settles into a disk around the young Earth — a disk that will later form into our Moon. While the giant impact described here has been simulated in detail in the past, most models have yet to incorporate the effects of magnetic fields into the giant impact and the subsequent evolution of the protolunar disk. In a new study, scientists Patrick Mullen and Charles Gammie (University of Illinois at Urbana-Champaign) develop state-of-the-art simulations that include weak initial magnetic fields. The authors show how these fields are amplified by turbulence in the collision, impacting the how the disk — and, ultimately, the Moon — evolves. To read more about their results, check out the original article below.

Citation

“A Magnetized, Moon-forming Giant Impact,” P. D. Mullen and C. F. Gammie 2020 ApJL 903 L15. doi:10.3847/2041-8213/abbffd

SDO AIA active region

How can we tell how much energy is leaking out of active regions on the Sun like the one shown in this Solar Dynamics Observatory (SDO) image above? Active regions are areas with especially strong magnetic fields, and they’re often associated with solar activity. But even when the Sun is generally quiet, these regions radiate energy away — and it’s important to understand how much.

To answer this question, scientists Maria Kazachenko (University of Colorado Boulder; National Solar Observatory) and Hugh Hudson (UC Berkeley; University of Glasgow, UK) used the Extreme Ultraviolet Variability Experiment on board SDO to measure unresolved spectra of the Sun as though it were a distant star. Kazachenko and Hudson compared data from periods when the Sun had no active regions to data from when only one active region was present, allowing them to identify the radiation specifically associated with the active region.

To learn more about the authors’ work, check out the original article below. And if you want to read more about “Sun-as-a-star” studies — studies like this one that treat the Sun as an unresolved source — you can check out this other recent ApJ study, which was announced in a press release today.

SDO data of active region

This full image from the article shows the magnetic fields (top two images) and SDO AIA 211 Å maps (bottom two images) for the Sun when one active region is present (left) and no active regions are present (right). The right column shows the disk-integrated magnetic flux (top) and a line-integrated spectrum (bottom) as the active region crosses the disk. [Kazachenko & Hudson 2020]

Citation

“Active Region Irradiance during Quiescent Periods: New Insights from Sun-as-a-star Spectra,” Maria D. Kazachenko and Hugh S. Hudson 2020 ApJ 901 64. doi:10.3847/1538-4357/abada6

plasmoid ejection

How could a magnetar — a powerfully magnetized neutron star — produce the brief flashes of radio emission and X-rays we’ve recently spotted from SGR 1935+2154, the first equivalent of a fast radio burst in our own galaxy? Magnetars have crusts that can suddenly crack and shear, shaking the magnetic fields of the star in what’s known as a magnetar quake. Using numerical simulations, a team of scientists led by Yajie Yuan (CCA, Flatiron Institute) has shown that waves from a magnetar quake can propagate to the star’s magnetosphere, converting into blobs of magnetized plasma. These plasmoids accelerate outward from the star, driving blast waves into the surrounding magnetar wind that generate simultaneous X-ray and radio bursts.

plasmoid ejection zoom-in

A zoom-in of ejecta propagating through the magnetosphere surrounding a magnetized neutron star. [Adapted from Yuan et al. 2020]

The simulation frame above spans roughly 15 x 108 cm by 30 x 108 cm. It provides a large-scale view of the magnetar and its magnetosphere 50 milliseconds into the authors’ simulation, as the ejected plasmoid blobs reach the outer regions of the magnetosphere. The image to the right is from just 10 milliseconds into the simulation, showing a detailed view of the ejecta early on. Both images are adapted from the original figures; to see the originals and to learn more about the authors’ results, check out the original article below.

Citation

“Plasmoid Ejection by Alfvén Waves and the Fast Radio Bursts from SGR 1935+2154,” Yajie Yuan et al 2020 ApJL 900 L21. doi:10.3847/2041-8213/abafa8

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

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