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14 different outputs from a supernova model

A research team led by Adam Burrows (Princeton University and the Institute for Advanced Study) has created the largest collection yet of state-of-the-art, three-dimensional core-collapse supernova simulations. The image above shows the results of several of the team’s simulations, showcasing the wide variety of structures and sizes attained by exploding stars just a few seconds after the stars’ outer layers rebounded off their collapsed cores. The smooth outer blue bubble shows the location of the expanding shock, while the more complex inner bubbles show the location of the ejected material. Red material is moving outward and blue material is moving inward. These simulations, which follow the collapse of stars with masses between 9 and 60 solar masses, allowed the team to find correlations between the properties of the explosions and the properties of the stars they came from. For example, the mass of the resulting neutron star is correlated with the compactness of the star. The simulations also predicted a correlation between the energy of the explosion and how asymmetrical it is, which can be tested in future studies. To learn more about the results of this study, be sure to check out the full research article linked below.

Citation

“Physical Correlations and Predictions Emerging from Modern Core-Collapse Supernova Theory,” Adam Burrows et al 2024 ApJL 964 L16. doi:10.3847/2041-8213/ad319e

star-forming region NGC 3603

The brightest giant star-forming region in the Milky Way has a new portrait, thanks to observations from a telescope flying through the stratosphere. A team led by James De Buizer (NASA Ames Research Center) paired new data from the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) with archival observations from the venerable Spitzer and Herschel infrared space telescopes to create the new image, shown above. The new observations yielded the highest-resolution data of the region at a wavelength of 25 microns (1 micron = 10-6 meter) and enabled the researchers to study star formation and search for structures around young stars. The clump of stars at the center of the image, HD 97950, is a starburst cluster that contains some of the most massive stars known. De Buizer’s team identified new massive young stellar objects, studied the dusty outflow of an evolved blue supergiant, and found several candidate high-mass proplyds: baby stars surrounded by dusty disks that are being blown away by intense radiation. To learn more about this enormous, dynamic star-forming region, be sure to check out the full article linked below.

Citation

“Surveying the Giant H II Regions of the Milky Way with SOFIA. VI. NGC 3603,” James M. De Buizer et al 2024 ApJ 963 55. doi:10.3847/1538-4357/ad19d1

map of matter in the universe, showing matter concentrations derived from measurements of the cosmic microwave background in grayscale and measurements of dusty galaxies in blue and orange contours

This image may look like a work of modern art, but it’s actually a map of the matter in our universe. A team led by Mathew Madhavacheril (University of Pennsylvania and Perimeter Institute for Theoretical Physics) developed this map from new measurements of the cosmic microwave background — the oldest light in the universe, which was emitted not long after the Big Bang. As this ancient light wends its way to us, it curves around the gravitational wells of intervening galaxies and galaxy clusters. By measuring the degree to which the microwave background is warped, researchers can determine how matter is scattered throughout the universe. The image above shows regions with lots of matter in white and regions without much matter in black. The orange and blue contours show the locations of dusty galaxies, which appear to be correlated with the location of matter measured from the microwave background. Researchers can test cosmological models with this new dataset, which covers nearly a quarter of the sky — the image here shows just a tiny fraction of the available data. To learn more about how researchers map matter and study structures in our universe, be sure to check out the original research article linked below.

Citation

“The Atacama Cosmology Telescope: DR6 Gravitational Lensing Map and Cosmological Parameters,” Mathew S. Madhavacheril et al 2024 ApJ 962 113. doi:10.3847/1538-4357/acff5f

simulation results showing a variety of minidisk behaviors

From millions of light-years away, how can we tell if a galaxy contains one supermassive black hole or two? It’s a tricky problem: the gas around single supermassive black holes glows across the electromagnetic spectrum and varies on timescales from hours to years, and it’s not obvious how adding a second black hole changes these behaviors. As a step toward differentiating the two scenarios, a team led by John Ryan Westernacher-Schneider (Leiden University and Clemson University) simulated the gas surrounding pairs of black holes. When binary black hole systems ensnare gas from their surroundings, the gas collects in a large accretion disk around both black holes and in smaller disks around the individual black holes. These smaller disks are called minidisks. Each frame above shows a simulated minidisk with different physical parameters. Because of instabilities, the simulated minidisks sometimes become extremely elongated, and if future work suggests that this elongation is likely to happen in real disks, it may provide a way to interpret variations in the light from distant sources and pinpoint binary black holes. To learn more about these minidisk simulations, be sure to check out the full article linked below.

Citation

“Eccentric Minidisks in Accreting Binaries,” John Ryan Westernacher-Schneider et al 2024 ApJ 962 76. doi:10.3847/1538-4357/ad1a17

Two diagrams illustrating the radiation and particles generated by a kilonova

The image above shows the radiation and particles generated by a kilonova, the explosion produced when the remnants of two massive stars collide. Kilonovae made headlines in 2017, when scientists observed gravitational waves and a kilonova from colliding neutron stars for the first time. Recently, a research team led by Haille Perkins (University of Illinois Urbana-Champaign) used information gleaned from the 2017 event to estimate the threat posed by a kilonova’s X-rays, gamma rays, and cosmic rays. Fortunately for us, a kilonova would have to be quite close for life on Earth to be endangered by its X-rays or gamma rays — within about 3 light-years for X-rays or 13 light-years for gamma rays. Even after the initial glow of the collision fades, though, there’s still danger: high-energy charged particles called cosmic rays pose a threat years after the dangerous radiation has passed, and a kilonova’s cosmic rays can be lethal out to 36 light-years away. Luckily, kilonovae are extremely rare, and the danger to life on Earth is minimal. As researchers observe more kilonovae and improve their models, we’ll be able to refine our understanding of how close is too close when it comes to kilonovae, the threat they pose to Earth, and the role they play in determining where in the universe life can form and flourish.

Citation

“Could a Kilonova Kill: A Threat Assessment,” Haille M. L. Perkins et al 2024 ApJ 961 170. doi:10.3847/1538-4357/ad12b7

three side-by side images of galaxy clusters and lensed quasar images

three side-by side images of galaxy clusters and lensed quasar images

Hubble Space Telescope images of the three lensed quasars studied in this work. The multiple lensed images of the quasars are indicated by the cyan letters. [Napier et al. 2023]

How fast is the universe expanding? Currently, the measured expansion rate of the universe, described by the Hubble constant, depends on how you measure it, creating a clash of constants called the Hubble tension. The apparent disagreement between the rate measured from fluctuations in the cosmic microwave background — the oldest light in the universe — and the rate obtained from measurements of certain types of exploding stars suggests that either new physics is afoot, or these measurements are muddied by systematic errors.

Finding other ways to measure the Hubble constant may help alleviate the tension. In a recent article, Kate Napier (University of Michigan) and collaborators describe their derivation of the Hubble constant from observations of distant quasars: extremely luminous galactic centers in the early universe that are powered by matter falling onto a supermassive black hole. The quasars in the team’s sample are gravitationally lensed by clusters of galaxies, meaning that their light has been bent and magnified by the immense gravity of the clusters. The resulting value of the Hubble constant is consistent with measurements made from both the cosmic microwave background and supernovae, but the technique isn’t yet precise enough to favor one value over the other. To learn more about the use of lensed quasars for measuring the Hubble constant, be sure to check out the full article linked below.

Citation

“Hubble Constant Measurement from Three Large-Separation Quasars Strongly Lensed by Galaxy Clusters,” Kate Napier et al 2023 ApJ 959 134. doi:10.3847/1538-4357/ad045a

results of the Swift Deep Galactic Plane Survey

results of the Swift Deep Galactic Plane Survey

The plane of the Milky Way through the eyes of the Swift Observatory. Click to see a high-resolution version. [O’Connor et al. 2023]

Researchers often discover faint X-ray sources only by chance, when they happen to occupy the same field of view as a bright source under investigation. Recently, as described in a research article led by Brendan O’Connor (Carnegie Mellon University), the team behind the Swift Deep Galactic Plane Survey took a more purposeful approach to finding faint X-ray sources in our galaxy, spending a collective 22 days observing the plane of the Milky Way with the Neil Gehrels Swift Observatory to do just that. Bright galactic X-ray sources tend to be flaring X-ray binaries — neutron stars or black holes that siphon material from a companion star, creating a super-hot accretion disk — and faint X-ray sources are likely cataclysmic variable stars, or magnetars and X-ray binaries in their quiescent state. The images above and to the right give a broad view of the results of the survey, which led to the discovery of 348 previously uncatalogued X-ray sources. The team found many objects near the brightness limit of their survey, suggesting that even more sensitive telescopes are needed to fully understand the X-ray sources in our galaxy. To learn more about the Milky Way’s population of faint X-ray sources, be sure to check out the full article below for more information about the first phase of the Swift Deep Galactic Plane Survey.

Citation

“The Swift Deep Galactic Plane Survey (DGPS) Phase I Catalog,” B. O’Connor et al 2023 ApJS 269 49. doi:10.3847/1538-4365/ad0228

up-close image of a solar flare

Solar flares, like the one photographed by the Solar Dynamics Observatory and shown above, are flashes of solar radiation powered by magnetic reconnection. Many solar flares are accompanied by immense eruptions of magnetized plasma called coronal mass ejections. In a recent research article, Maria Kazachenko (University of Colorado Boulder and National Solar Observatory) explored why some solar flares, called eruptive flares, come with a coronal mass ejection, while others, called confined flares, do not. Kazachenko analyzed 480 solar flares, from middle-of-the-pack C-class flares to the most energetic X-class flares, cataloging the thermodynamic and magnetic properties of each flare and noting whether it was eruptive or confined. Confined flares tend to arise from active regions — areas of the solar surface with strong magnetic fields — that are larger and more strongly magnetic, and a smaller fraction of the active region’s magnetic field undergoes magnetic reconnection during a confined flare. For the first time, Kazachenko showed that magnetic reconnection happens more rapidly in confined flares than eruptive flares. To learn more about the properties of confined and eruptive flares, be sure to check out the full research article linked below

Citation

“A Database of Magnetic and Thermodynamic Properties of Confined and Eruptive Solar Flares,” Maria D. Kazachenko 2023 ApJ 958 104. doi:10.3847/1538-4357/ad004e

four sunspot umbrae within a single penumbra

Sunspots are dark, relatively cool regions of the Sun where magnetic flux pokes through the Sun’s surface. Sunspots have a two-toned appearance consisting of one or more dark regions, or umbrae (from Latin for “shade”), surrounded by a slightly lighter region called a penumbra. Over the past several decades, scientists have observed oscillations in sunspot umbrae with periods of 3 and 5 minutes. The causes of these oscillations aren’t yet known, though researchers generally agree that their source lies deeper in the Sun’s interior. To learn more about umbral oscillations, a team led by Wei Wu (Chinese Academy of Sciences and University of Chinese Academy of Sciences) analyzed images of sunspots, including the sunspot with four umbrae pictured above. Wu’s team found that the oscillations of umbrae within a shared penumbra are loosely correlated, suggesting that the waves travel horizontally from umbra to umbra, and stronger correlations might indicate a shared source. The team also analyzed observations of the chromosphere and corona above the sunspots and found that sunspot oscillations can, in some cases, travel upward through the Sun’s atmosphere. To learn more about the study of umbral oscillations, be sure to check out the full article linked below.

Citation

“Propagation Properties of Sunspots Umbral Oscillations in Horizontal and Vertical Directions,” Wei Wu et al 2023 ApJ 958 10. doi:10.3847/1538-4357/acf457

two images of the pulsar wind nebula named the Cosmic Hand

Some 16,000 light-years from Earth, a ghostly hand glows with X-ray light. The distinctive “Cosmic Hand” is a pulsar wind nebula: an X-ray-emitting cloud powered by charged-particle winds from the spinning remnant of a massive star that exploded as a supernova. In X-ray images, the Cosmic Hand has a thumb and three fingers formed by brighter ridges of emission and a delicate wrist illuminated by the pulsar’s powerful jet. Recently, a team led by Roger Romani (Stanford University) used the Imaging X-ray Polarimetry Explorer (IXPE) to make the first observations of polarized X-ray light from the Cosmic Hand. The images above show the degree of polarization detected and the direction of the derived magnetic field (left image, white and yellow bars atop an X-ray image from the Chandra X-ray Observatory) and the 2–8-kiloelectronvolt brightness (right image, greyscale). The new measurements show that the polarization generally follows the structure of the nebula, especially the thumb and the arched region surrounding the jet. To learn more about the structure and magnetic fields of this pulsar wind nebula, be sure to check out the full article linked below.

Citation

“The Polarized Cosmic Hand: IXPE Observations of PSR B1509−58/MSH 15−52,” Roger W. Romani et al 2023 ApJ 957 23. doi:10.3847/1538-4357/acfa02

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