Saturday, September 09, 2023

SPACE

 

New cosmological constraints on the nature of dark matter


Peer-Reviewed Publication

NATIONAL INSTITUTES OF NATURAL SCIENCES

Dark matter fluctuations in the lens system MG J0414+0534 

IMAGE: DARK MATTER FLUCTUATIONS IN THE LENS SYSTEM MG J0414+0534. THE WHITISH BLUE COLOR REPRESENTS THE GRAVITATIONALLY LENSED IMAGES OBSERVED BY ALMA. THE CALCULATED DISTRIBUTION OF DARK MATTER IS SHOWN IN ORANGE; BRIGHTER REGIONS INDICATE HIGHER CONCENTRATIONS OF DARK MATTER AND DARK ORANGE REGIONS INDICATE LOWER CONCENTRATIONS. view more 

CREDIT: ALMA(ESO/NAOJ/NRAO), K. T. INOUE ET AL.



New research has revealed the distribution of dark matter in never before seen detail, down to a scale of 30,000 light-years. The observed distribution fluctuations provide better constraints on the nature of dark matter. 

 

Mysterious dark matter accounts for most of the matter in the Universe. Dark matter is invisible and makes itself know only through its gravitational effects. Dark matter has never been isolated in a laboratory, so researchers must rely on “natural experiments” to study it.  

 

One type of natural experiment is a gravitational lens. Sometimes by random chance, two objects at different distances in the Universe will lie along the same line-of-sight when seen from Earth. When this happens, the spatial curvature caused by the matter around the foreground object acts like a lens, bending the path of light from the background object and making a lensed image. However, it is difficult to achieve the high resolution to detect clumps of dark matter which are less massive than galaxies in natural experiments, so the exact nature of dark matter has been poorly constrained. 

 

A team of Japanese researchers led by Professor Kaiki Taro Inoue at Kindai University used ALMA (Atacama Large Millimeter/submillimeter Array) to study the gravitational lens system known as MG J0414+0534 in the direction of the constellation Taurus. In this system, the foreground object forms not one, but four images of the background object due to the gravitational force of a massive galaxy acting on the light. With the help of the bending effect and their new data analysis method, the team was able to detect fluctuations in the dark matter distribution along the line-of-sight in higher resolution than ever before, down to a scale of 30,000 light-years. 

  

A conceptual diagram of the gravitational lens system MG J0414+0534. Dark matter associated with the lensing galaxy is shown in pale blue and white. Dark matter in intergalactic space is shown in orange. Solid lines show the actual paths of the radio waves which are bent by gravity. Dotted lines show the apparent observed positions of the lensed images.

CREDIT

NAOJ, K. T. Inoue

The new constraints provided by the observed distribution are consistent with models for slow moving, or “cold,” dark matter particles. 

 

In the future the team plans to further constrain the nature of dark matter with additional observations. 

NASA’s Swift learns a new trick, spots a snacking black hole



Peer-Reviewed Publication

NASA/GODDARD SPACE FLIGHT CENTER

Repeating TDE 

IMAGE: IN THIS ARTIST'S CONCEPT, A SUPERMASSIVE BLACK HOLE PULLS A STREAM OF GAS OFF A STAR THAT PASSES TOO CLOSE. view more 

CREDIT: NASA’S GODDARD SPACE FLIGHT CENTER/CHRIS SMITH (USRA/GESTAR)




Using NASA’s Neil Gehrels Swift Observatory, which launched in 2004, scientists have discovered a black hole in a distant galaxy repeatedly nibbling on a Sun-like star. The object heralds a new era of Swift science made possible by a novel method for analyzing data from the satellite’s X-ray Telescope (XRT).

“Swift’s hardware, software, and the skills of its international team have enabled it to adapt to new areas of astrophysics over its lifetime,” said Phil Evans, an astrophysicist at the University of Leicester in the United Kingdom and longtime Swift team member. “Neil Gehrels, the mission’s namesake, oversaw and encouraged many of those transitions. Now, with this new ability, it’s doing even more cool science.”

Evans led a study about the unlucky star and its hungry black hole, collectively called Swift J023017.0+283603 (or Swift J0230 for short), which was published on Sept. 7 in Nature Astronomy.

When a star strays too close to a monster black hole, gravitational forces create intense tides that break the star apart into a stream of gas. The leading edge swings around the black hole, and the trailing edge escapes the system. These destructive episodes are called tidal disruption events. Astronomers see them as flares of multiwavelength light created when the debris collides with a disk of material already orbiting the black hole.

Recently, astronomers have been investigating variations on this phenomena, which they call partial or repeating tidal disruptions.

During these events, every time an orbiting star passes close to a black hole, the star bulges outward and sheds material, but survives. The process repeats until the star loses too much gas and finally breaks apart. The characteristics of the individual star and black hole system determine what kind of emission scientists observe, creating a wide array of behaviors to categorize.

Previous examples include an outburst that occurred every 114 days, potentially caused by a giant star orbiting a black hole with 78 million times the Sun’s mass. Another recurred every nine hours around a black hole with 400,000 times the Sun’s mass, likely caused by an orbiting stellar cinder called a white dwarf.

On June 22, 2022, the XRT captured Swift J0230 for the first time. It lit up in a galaxy around 500 million light-years away in the northern constellation Triangulum. Swift’s XRT observed nine additional outbursts from the same location roughly every few weeks.

Evans and his team propose that Swift J0230 is a repeating tidal disruption of a Sun-like star orbiting a black hole with over 200,000 times the Sun’s mass. They estimate the star loses around three Earth masses of material on each pass. This system provides a bridge between other types of suspected repeating disruptions and allowed scientists to model how interactions between different star types and black hole sizes affect what we observe. 

“We searched and searched for the event brightening in the data collected by Swift’s Ultraviolet/Optical Telescope,” said Alice Breeveld, a research fellow at the University College London’s Mullard Space Science Laboratory (MSSL) who has worked on the instrument since before the satellite launched. “But there wasn’t any sign of it. The galaxy’s variability was entirely in X-rays. That helped rule out some other potential causes.”

Swift J0230’s discovery was possible thanks to a new, automated search of XRT observations, developed by Evans, called the Swift X-ray Transient Detector.

After the instrument observes a portion of the sky, the data is transmitted to the ground, and the program compares it to previous XRT snapshots of the same spot. If that portion of the X-ray sky has changed, scientists get an alert. In the case of Swift J0230, Evans and his colleagues were able to rapidly coordinate additional observations of the region.

Swift was originally designed to study gamma-ray bursts, the most powerful explosions in the cosmos. Since the satellite launched, however, scientists have recognized its ability to study a whole host of celestial objects, like tidal disruptions and comets.

“Swift J0230 was discovered only about two months after Phil launched his program,” said S. Bradley Cenko, the mission’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It bodes well for the detector’s ability to identify other transient events and for Swift’s future exploring new spaces of science.”

Goddard manages the Swift mission in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico, and Northrop Grumman Space Systems in Dulles, Virginia. Other partners include Leicester, MSSL, Brera Observatory in Italy, and the Italian Space Agency.

Study hints at the existence of the closest black holes to Earth in the Hyades star cluster


Black holes are one of the most mysterious and fascinating phenomena in the Universe

Peer-Reviewed Publication

UNIVERSITY OF BARCELONA

Study hints at the existence of the closest black holes to Earth in the Hyades star cluster 

IMAGE: IMAGE OF THE HYADES STAR CLUSTER view more 

CREDIT: JOSE MTANOUS




A paper published in the journal Monthly Notices of the Royal Astronomical Society hints at the existence of several black holes in the Hyades cluster — the closest open cluster to our solar system — which would make them the closest black holes to Earth ever detected.  The study results from a collaboration between a group of scientists led by Stefano Torniamenti, from the University of Padua (Italy), with the significant participation of with Mark Gieles, ICREA professor at the Faculty of Physics, the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Institute of Space Studies of Catalonia (IEEC), and Friedrich Anders (ICCUB-IEEC).

Specifically, the finding took place during a research stay of the expert Stefano Torniamenti at the ICCUB, one of the research units that make up the IEEC.

Black holes in the Hyades star cluster?

Since their discovery, black holes have been one of the most mysterious and fascinating phenomena in the Universe and have become the object of study for researchers all over the world. This is particularly true for small black holes because they have been observed during the detection of gravitational waves. Since the detection of the first gravitational waves in 2015, experts have observed many events that correspond to mergers of low-mass black hole pairs. 

For the published study, the team of astrophysicists used simulations that track the motion and evolution of all the stars in the Hyades — located at a distance from the Sun of about 45 parsecs or 150 light-years — to reproduce their current state.

Open clusters are loosely bound groups of hundreds of stars that share certain properties such as age and chemical characteristics. The simulation results were compared with the actual positions and velocities of the stars in the Hyades, which are now known precisely from observations made by the European Space Agency's (ESA) Gaia satellite.

"Our simulations can only simultaneously match the mass and size of the Hyades if some black holes are present at the centre of the cluster today (or until recently)", says Stefano Torniamenti, postdoctoral researcher at the University of Padua and first author of the paper.

The observed properties of the Hyades are best reproduced by simulations with two or three black holes at present, although simulations where all the black holes have been ejected (less than 150 million years ago, roughly the last quarter of the cluster's age) can still give a good match, because the evolution of the cluster could not erase the traces of its previous black hole population.

The new results indicate that the Hyades-born black holes are still inside the cluster, or very close to the cluster. This makes them the closest black holes to the Sun, much closer than the previous candidate (namely the black hole Gaia BH1, which is 480 parsecs from the Sun).

In recent years, the breakthrough of the Gaia space telescope has made it possible for the first time to study the position and velocity of open cluster stars in detail and to identify individual stars with confidence.

"This observation helps us understand how the presence of black holes affects the evolution of star clusters and how star clusters in turn contribute to gravitational wave sources", says Mark Gieles, a member of the UB Department of Quantum Physics and Astrophysics and host of the first author in Barcelona. "These results also give us insight into how these mysterious objects are distributed across the galaxy”.

The new study is the result of close collaboration between the University of Padova, ICUBB-IEEC, the University of Cambridge (United Kingdome), the European Southern Observatory (ESO) and the National Sun Yat-sen University (China).
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Webb reveals new structures within iconic supernova

Reports and Proceedings

NASA/GODDARD SPACE FLIGHT CENTER

Webb’s NIRCam (Near-Infrared Camera) captured this detailed image of SN 1987A (Supernova 1987A) 

IMAGE: WEBB’S NIRCAM (NEAR-INFRARED CAMERA) CAPTURED THIS DETAILED IMAGE OF SN 1987A (SUPERNOVA 1987A), WHICH HAS BEEN ANNOTATED TO HIGHLIGHT KEY STRUCTURES. AT THE CENTER, MATERIAL EJECTED FROM THE SUPERNOVA FORMS A KEYHOLE SHAPE. JUST TO ITS LEFT AND RIGHT ARE FAINT CRESCENTS NEWLY DISCOVERED BY WEBB. BEYOND THEM AN EQUATORIAL RING, FORMED FROM MATERIAL EJECTED TENS OF THOUSANDS OF YEARS BEFORE THE SUPERNOVA EXPLOSION, CONTAINS BRIGHT HOT SPOTS. EXTERIOR TO THAT IS DIFFUSE EMISSION AND TWO FAINT OUTER RINGS. IN THIS IMAGE BLUE REPRESENTS LIGHT AT 1.5 MICRONS (F150W), CYAN 1.64 AND 2.0 MICRONS (F164N, F200W), YELLOW 3.23 MICRONS (F323N), ORANGE 4.05 MICRONS (F405N), AND RED 4.44 MICRONS (F444W). view more 

CREDIT: CREDITS: NASA, ESA, CSA, M. MATSUURA (CARDIFF UNIVERSITY), R. ARENDT (NASA’S GODDARD SPACEFLIGHT CENTER & UNIVERSITY OF MARYLAND, BALTIMORE COUNTY), C. FRANSSON (STOCKHOLM UNIVERSITY), AND J. LARSSON (KTH ROYAL INSTITUTE OF TECHNOLOGY). IMAGE PROCESSING: A. PAGAN



NASA’s James Webb Space Telescope has begun the study of one of the most renowned supernovae, SN 1987A (Supernova 1987A). Located 168,000 light-years away in the Large Magellanic Cloud, SN 1987A has been a target of intense observations at wavelengths ranging from gamma rays to radio for nearly 40 years, since its discovery in February of 1987. New observations by Webb’s NIRCam (Near-Infrared Camera) provide a crucial clue to our understanding of how a supernova develops over time to shape its remnant.

This image reveals a central structure like a keyhole. This center is packed with clumpy gas and dust ejected by the supernova explosion. The dust is so dense that even near-infrared light that Webb detects can’t penetrate it, shaping the dark “hole” in the keyhole.

 

A bright, equatorial ring surrounds the inner keyhole, forming a band around the waist that connects two faint arms of hourglass-shaped outer rings. The equatorial ring, formed from material ejected tens of thousands of years before the supernova explosion, contains bright hot spots, which appeared as the supernova’s shock wave hit the ring. Now spots are found even exterior to the ring, with diffuse emission surrounding it. These are the locations of supernova shocks hitting more exterior material.

 

While these structures have been observed to varying degrees by NASA’s Hubble and Spitzer Space Telescopes and Chandra X-ray Observatory, the unparalleled sensitivity and spatial resolution of Webb revealed a new feature in this supernova remnant – small crescent-like structures. These crescents are thought to be a part of the outer layers of gas shot out from the supernova explosion. Their brightness may be an indication of limb brightening, an optical phenomenon that results from viewing the expanding material in three dimensions. In other words, our viewing angle makes it appear that there is more material in these two crescents than there actually may be.

  

Webb’s NIRCam (Near-Infrared Camera) captured this detailed image of SN 1987A (Supernova 1987A), which has been annotated to highlight key structures. At the center, material ejected from the supernova forms a keyhole shape. Just to its left and right are faint crescents newly discovered by Webb. Beyond them an equatorial ring, formed from material ejected tens of thousands of years before the supernova explosion, contains bright hot spots. Exterior to that is diffuse emission and two faint outer rings. In this image blue represents light at 1.5 microns (F150W), cyan 1.64 and 2.0 microns (F164N, F200W), yellow 3.23 microns (F323N), orange 4.05 microns (F405N), and red 4.44 microns (F444W).

CREDIT

Credits: NASA, ESA, CSA, M. Matsuura (Cardiff University), R. Arendt (NASA’s Goddard Spaceflight Center & University of Maryland, Baltimore County), C. Fransson (Stockholm University), and J. Larsson (KTH Royal Institute of Technology). Image Processing: A. Pagan

The high resolution of these images is also noteworthy. Before Webb, the now-retired Spitzer telescope observed this supernova in infrared throughout its entire lifespan, yielding key data about how its emissions evolved over time. However, it was never able to observe the supernova with such clarity and detail.

Despite the decades of study since the supernova’s initial discovery, there are several mysteries that remain, particularly surrounding the neutron star that should have been formed in the aftermath of the supernova explosion. Like Spitzer, Webb will continue to observe the supernova over time. Its NIRSpec (Near-Infrared Spectrograph) and MIRI (Mid-Infrared Instrument) instruments will offer astronomers the ability to capture new, high-fidelity infrared data over time and gain new insights into the newly identified crescent structures. Further, Webb will continue to collaborate with Hubble, Chandra, and other observatories to provide new insights into the past and future of this legendary supernova.

The James Webb Space Telescope is the world's premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Hot Jupiter blows its top


Stampede2 simulations help capture helium gas clouds escaping distant planet

Peer-Reviewed Publication

UNIVERSITY OF TEXAS AT AUSTIN

Gas Escapes Planet HAT-P-32b 

IMAGE: THE PLANET HAT-P-32B IS LOSING SO MUCH OF ITS ATMOSPHERIC HELIUM THAT THE TRAILING GAS TAILS ARE AMONG THE LARGEST STRUCTURES YET KNOWN ANY PLANET OUTSIDE OUR SOLAR SYSTEM. SIMULATION ‘SLICE’ THROUGH THE ORBITAL PLANE APPROXIMATING THE HAT-P-32 A + B SYSTEM. view more 

CREDIT: ZHANG ET AL., SCI. ADV. 9, EADF8736 (2023).



A planet about 950 light years from Earth could be the Looney Tunes’ Yosemite Sam equivalent of planets, blowing its atmospheric ‘top’ in spectacular fashion. 

The planet called HAT-P-32b is losing so much of its atmospheric helium that the trailing gas tails are among the largest structures yet known of an exoplanet, a planet outside our solar system, according to observations by astronomers. 

Three-dimensional (3D) simulations on the Stampede2 supercomputer of the Texas Advanced Computing Center (TACC) helped model the flow of the planet’s atmosphere, based on data from the Hobby-Eberly Telescope of The University of Texas at Austin's McDonald Observatory. The scientists hope to widen their planet-observing net and survey 20 additional star systems to find more planets losing their atmosphere and learn about their evolution.

“We have monitored this planet and the host star with long time series spectroscopy, observations made of the star and planet over a couple of nights. And what we found is there's a gigantic helium gas tail that is associated with the planet. The tail is large — about 53 times the planet’s radius — formed by gas that’s escaping from the planet,” said Zhoujian Zhang, a postdoctoral fellow in the Department of Astronomy & Astrophysics, University of California Santa Cruz. 

Zhang is the lead author in a study on the helium tail detected from HAT-P 32b that was published in Science Advances June 2023. The science team used data from the Habitable Planet Finder spectrograph, an instrument on the Hobby-Eberly telescope, which provides high spectral resolution of light in near infrared wavelengths. 

The planet HAT-P-32b was discovered in 2011 using spectroscopic data from the Hungarian-made Automated Telescope Network. It’s known as a ‘hot Jupiter,’ a gas giant similar to our neighboring planet Jupiter, but with a radius twice as large. This hot Jupiter hugs closely in orbit to its host star, about three percent the distance from the Earth to the Sun. Its orbital period — what we consider a year here on Earth — is only 2.15 days, and this proximity to the star scorches it with both long and short wave radiation.

The main motivation for the scientists’ interest in studying hot Jupiters is their pursuit of the mystery of the Neptunian desert, the inexplicable relative scarcity on average of intermediate-mass planets, or sub-Jupiters, with short orbital periods.

“One of the potential explanations is that maybe the planets are losing their mass,” Zhang offered. “If we can capture planets in the process of losing their atmosphere, then we can study how fast the planet is losing their mass and what are the mechanisms that cause their atmosphere to escape from the planet. It's good to have some examples to see like the HAT-P-32b process in action.”

The light analyzed in the study comes from the star HAT-P-32 A. It’s slightly hotter and similar in size to our own sun. The analyzed light is not just straight starlight. As the planet passes in front of the star, for just a couple of hours the starlight gets filtered the most by the planet’s gassy atmosphere. This filtering, called absorption, reveals features of the transiting planet, in this case huge outflows of helium when the spectra were analyzed.

Zhang and colleagues used a technique called transmission spectroscopy to separate the starlight into its component frequencies, like a prism separates sunlight into a rainbow spectrum. Gaps in the spectrum indicate light being absorbed by elements in the gaseous atmosphere of HAT-P-32b. 

“What we see in our data is that when the planet is transiting the star, we see there's deeper helium absorption lines. The helium absorption is stronger than what we expect from the stellar atmosphere. This excess helium absorption should be caused by the planet’s atmosphere. When the planet is transiting, its atmosphere is so huge that it blocks part of the atmosphere that absorbs the helium line, and that causes this excess absorption. That's how we discovered the HAT-P-32b to be an interesting planet,” Zhang said.

It got more interesting as they developed 3D hydrodynamical simulations of the HAT-P-32b and host star, led by Antonija Oklopčić, Anton Pannekoek Institute for Astronomy, University of Amsterdam; and Morgan MacLeod, Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, Harvard University.

The models examined the interactions between the planetary outflow and stellar winds in the tidal gravitational field of the extrasolar system. The models showed columnar tails of planetary outflow both leading and trailing the planet along its orbital path with excess helium absorption even far from the transit points that matched observations. What is more, the models suggest complete loss of the atmosphere in about 4 x 10e10 Earth years.


“We made use of TACC's Stampede2 system's Intel Skylake nodes for our calculations,” MacLeod said. “This computation involves tracking flow as it accelerates from a slow-moving subsonic 'atmosphere' near the planet to a supersonic wind as it moves further away. The HAT-P-32b system was identified to have a large-scale outflow similar in size to the planet's orbit around the star. Taken together, these requirements suggest the need for a stable, high-accuracy algorithm for solving three-dimensional gas dynamics.”

The modelers utilized the Athena++ hydrodynamic software and a custom problem setup to do their calculation on Stampede2. With it they solve the equations of gas dynamics in a rotating frame of reference that matches the planet's orbital motion. Athena++ is a Eulerian code -- the flow is discretized with volume elements -- and they used nested layers of mesh refinement to capture the large-scale star-planet system along with the much smaller scale of the atmosphere near the planet's surface. 

“Using the TACC HPC systems is a joy,” MacLeod said. “A few things go into this -- the first, and most important is the level of support. Whenever I have a problem, I can call the support line, get help, and get back to doing the science that I am best at. Secondly, the vast majority of my time goes into developing and validating model results, rather than running a single, full-scale calculation. The TACC systems are incredibly well set up for this reality, and it hugely speeds up the pace of development. Being able to run test calculations through the development queues or submit larger calculations of a range of sizes in the lead up to an eventual final model is crucial and effective in these environments.”

Looking ahead, the scientists hope to continue to develop sophisticated 3D models that capture effects such as atmospheric mixing of gases and even winds within the atmosphere on more distant worlds hundreds and even thousands of light years away.

“Now is the time to have supercomputers with the computational power to make this happen," Zhang said. "We need the computers to make real predictions based on recent advances in the theory and to explain the data. Supercomputers bridge the model and the data."

 “The best thing we can do is watch the night sky and try to recreate what we see through computer modeling," MacLeod concluded. "Our universe is complicated. This means we need to have access to the absolute best supercomputing systems." 

The study, Giant tidal tails of helium escaping the hot Jupiter HAT- P-32 b, was published June 7, 2023, in the journal Science Advances. The study authors are Zhoujian Zhang of UCSC; Caroline V. Morley, Michael Gully-Santiago, Jessica Luna, Quang H. Tran, Daniel M. Krolikowski, William D. Cochran, Brendan P. Bowler, Michael Endl, Gudmundur Stefánsson, Benjamin M. Tofflemire, Gregory R. Zeimann of UT Austin; Morgan MacLeod of Harvard University; Antonija Oklopčić of University of Amsterdam; Joe P. Ninan of Tata Institute of Fundamental Research; Suvrath Mahadevan of The Pennsylvania State University; Andrew Vanderburg of MIT. Funding came from the NASA Exoplanets Research Program grant number 80NSSC20K0257; National Science Foundation grant 2108801; NASA Hubble Fellowship grants HST-HF2- 51522.001-A. Support also came from NSF grants AST-1006676, AST-1126413, AST-1310875, AST-1310885, AST 2009889, AST 2009982, ATI 2009955, and AAG 2108512 and the Heising-Simons Foundation via grant 2017- 0494. 

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