Could Supermassive Stars Explain How This Galaxy Got Its Nitrogen?

This image of the northern Great Observatories Origins Deep Survey (GOODS) field shows the location of the galaxy GN-z11, a closeup of which is shown in the zoomed-in image. Credit: NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)

One of the most distant known galaxies, GN-z11, might be unusually rich in nitrogen. Researchers suggest that supermassive stars could provide a pathway for nitrogen to be enhanced in this early galaxy.

Artist’s impression of the jet from an active galactic nucleus directed toward Earth.
Credit: NASA/Goddard Space Flight Center Conceptual Image Lab

A New Look at a Distant Galaxy

GN-z11 was once the most distant cosmic object known. This luminous galaxy was discovered with the Hubble Space Telescope in 2015, and now JWST has turned its exquisite spectrometer to the task of precisely determining the galaxy’s distance and extracting its properties.

A new spectrum of GN-z11 shows bright emission lines from several atoms including nitrogen. Strong emission lines in a galaxy’s spectrum can mean that the galaxy hosts an active galactic nucleus — a supermassive black hole that’s consuming superheated gas from its surroundings — but some researchers suspect that’s not the case for GN-z11. Instead, this galaxy’s strong nitrogen lines might mean that it’s unusually rich in that element, but it’s not clear where this supply of nitrogen might have come from. In a recent research article, Chris Nagele and Hideyuki Umeda of the University of Tokyo suggest that supermassive stars might be the cause.

Supermassive Stars in the Spotlight

Supermassive stars are hypothesized to contain more than a hundred times the mass of the Sun, and the most massive of them might have clocked in at more than 100,000 solar masses. If stars at the upper end of this mass range existed in the early universe, they could give rise to the seeds of supermassive black holes and explain the properties of galaxies like GN-z11.

Nagele and Umeda simulated the evolution of supermassive stars of 1,000, 10,000, 50,000, and 100,000 solar masses. Each of these enormous stars started out with an abundance of metals (elements heavier than helium) just one-tenth the Sun’s, which is representative of the conditions a few hundred million years after the Big Bang. The team’s simulations combined fluid dynamics, nuclear reactions, and general relativity to follow the stars as they evolve. The vastly different masses of the simulated stars resulted in vastly different outcomes; the 100,000-solar-mass star exploded and the 50,000-solar-mass star collapsed before the end of the hydrogen-burning phase, while the two less weighty stars evolved off the main sequence without incident.

Abundances of chemical elements relative to the amount contained in the Sun. Note that the higher-mass models produce super-solar nitrogen (Z=7) and sub-solar oxygen (Z=8), while the lower-mass models produce super-solar amounts of both elements. Credit: Nagele and Umeda 2023

A Matter of Timing

How long each star lived before exploding or collapsing determined how much it enriched its surroundings with metals, and it also determined the ratios of various metal species relative to one another. For example, the longer-lived lower-mass stars produced enhanced amounts of both nitrogen and oxygen via their powerful stellar winds. Because GN-z11 does not show signs of abundant oxygen, this means that 1,000- and 10,000-solar-mass stars are unlikely sources of the galaxy’s nitrogen.

The more massive stars, though, produced enhanced amounts of nitrogen but not oxygen, leading to a chemical abundance pattern that is consistent with what we see for GN-z11. Nagele and Umeda note that there are nuances that will need to be explored by future simulations with finer time resolution, but as of now supermassive stars remain a promising candidate source for GN-z11’s nitrogen. And as for the origins of the stars themselves, the authors pointed out that one way supermassive stars could form is through the collision of massive galaxies — and new observations show a “haze” around GN-z11 that might be a sign of such a collision.

Citation

“Multiple Channels for Nitrogen Pollution by Metal-enriched Supermassive Stars and Implications for GN-z11,” Chris Nagele and Hideyuki Umeda 2023 ApJL 949 L16.doi:10.3847/2041-8213/acd550

Source:American Astronomical Society/AAS Nova

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Webb Maps Surprisingly Large Plume Jetting From Saturn’s Moon Enceladus

Enceladus Plume (Webb [NIRSpec] and Cassini Image)
Credits: Image: NASA, ESA, CSA, Geronimo Villanueva (NASA-GSFC)
Image Processing: Alyssa Pagan (STScI)

Enceladus Water Emission Spectrum (NIRSpec IFU)
Credits: Science: Geronimo Villanueva (NASA-GSFC)
Illustration: NASA, ESA, CSA, STScI, Leah Hustak (STScI)

Release Images | Release Videos

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A water vapor plume from Saturn’s moon Enceladus spanning more than 6,000 miles – nearly the distance from Los Angeles, California to Buenos Aires, Argentina – has been detected by researchers using NASA’s James Webb Space Telescope. Not only is this the first time such a water emission has been seen over such an expansive distance, but Webb is also giving scientists a direct look, for the first time, at how this emission feeds the water supply for the entire system of Saturn and its rings.

Enceladus, an ocean world about four percent the size of Earth, just 313 miles across, is one of the most exciting scientific targets in our solar system in the search for life beyond Earth. Sandwiched between the moon’s icy outer crust and its rocky core is a global reservoir of salty water. Geyser-like volcanos spew jets of ice particles, water vapor, and organic chemicals out of crevices in the moon’s surface informally called ‘tiger stripes.’

Previously, observatories have mapped jets hundreds of miles from the moon’s surface, but Webb’s exquisite sensitivity reveals a new story.

“When I was looking at the data, at first, I was thinking I had to be wrong. It was just so shocking to detect a water plume more than 20 times the size of the moon,” said lead author Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The water plume extends far beyond its release region at the southern pole.”

The length of the plume was not the only characteristic that intrigued researchers. The rate at which the water vapor is gushing out, about 79 gallons per second, is also particularly impressive. At this rate, you could fill an Olympic-sized swimming pool in just a couple of hours. In comparison, doing so with a garden hose on Earth would take more than 2 weeks.

The Cassini orbiter spent over a decade exploring the Saturnian system, and not only imaged the plumes of Enceladus for the first time but flew directly through them and sampled what they were made of. While Cassini’s position within the Saturnian system provided invaluable insights into this distant moon, Webb’s unique view from the Sun-Earth Lagrange Point 2 one million miles from Earth, along with the remarkable sensitivity of its Integral Field Unit aboard the NIRSpec (Near-Infrared Spectrograph) Instrument, is offering new context.

“The orbit of Enceladus around Saturn is relatively quick, just 33 hours. As it whips around Saturn, the moon and its jets are basically spitting off water, leaving a halo, almost like a donut, in its wake,” said Villanueva. “In the Webb observations, not only was the plume huge, but there was just water absolutely everywhere.”

This fuzzy donut of water that appeared ‘everywhere,' described as a torus, is co-located with Saturn’s outermost and widest ring – the dense “E-ring.”

The Webb observations directly demonstrate how the moon’s water vapor plumes feed the torus. By analyzing the Webb data, astronomers have determined roughly 30 percent of the water stays within this torus, and the other 70 percent escapes to supply the rest of the Saturnian system of water.

In the coming years, Webb will serve as the primary observation tool for ocean moon Enceladus, and discoveries from Webb will help inform future solar system satellite missions that will look to explore the subsurface ocean’s depth, how thick the ice crust is, and more.

“Right now, Webb provides a unique way to directly measure how water evolves and changes over time across Enceladus' immense plume, and as we see here, we will even make new discoveries and learn more about the composition of the underlying ocean,” added co-author Stefanie Milam at NASA Goddard. “Because of Webb’s wavelength coverage and sensitivity, and what we’ve learned from previous missions, we have an entire new window of opportunity in front of us.”

Webb’s observations of Enceladus were completed under Guaranteed Time Observation (GTO) program 1250. The initial goal of this program is to demonstrate the capabilities of Webb in a particular area of science and set the stage for future studies.

“This program was essentially a proof of concept after many years of developing the observatory, and it’s just thrilling that all this science has already come out of quite a short amount of observation time,” said Heidi Hammel of the Association of Universities for Research in Astronomy, Webb interdisciplinary scientist and leader of the GTO program.

The team’s results were recently accepted for publication in Nature Astronomy on May 17, and a pre-print is available here.

The James Webb Space Telescope is the world's premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe 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 CSA (Canadian Space Agency).

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Source: NASA's James Webb Space Telescope/News

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NASA Scientists Make First Observation of a Polar Cyclone on Uranus

NASA scientists used microwave observations to spot the first polar cyclone on Uranus, seen here as a light-colored dot to the right of center in each image of the planet. The images use wavelength bands K, Ka, and Q, from left. To highlight cyclone features, a different color map was used for each. Credits: NASA/JPL-Caltech/VLA

This image of Uranus was taken by NASA’s Voyager 2 spacecraft in 1986.
Credits: NASA/JPL-Caltech/VLA

 

Scientists used ground-based telescopes to get unprecedented views, thanks to the giant planet’s position in its long orbit around the Sun.

For the first time, NASA scientists have strong evidence of a polar cyclone on Uranus. By examining radio waves emitted from the ice giant, they detected the phenomenon at the planet’s north pole. The findings confirm a broad truth about all planets with substantial atmospheres in our solar system: Whether the planets are composed mainly of rock or gas, their atmospheres show signs of a swirling vortex at the poles.

Scientists have long known that Uranus’ south pole has a swirling feature. NASA’s Voyager 2 imaging of methane cloud tops there showed winds at the polar center spinning faster than over the rest of the pole. Voyager’s infrared measurements observed no temperature changes, but the new findings, published in Geophysical Research Letters, do.

Using huge radio antenna dishes of the Very Large Array in New Mexico, they peered below the ice giant’s clouds, determining that the circulating air at the north pole seems to be warmer and drier – the hallmarks of a strong cyclone. Collected in 2015, 2021, and 2022, the observations went deeper into Uranus’ atmosphere than any before.

“These observations tell us a lot more about the story of Uranus. It’s a much more dynamic world than you might think,” said lead author Alex Akins of NASA’s Jet Propulsion Laboratory in Southern California. “It isn’t just a plain blue ball of gas. There’s a lot happening under the hood.”

Uranus is showing off more these days, thanks to the planet’s position in orbit. It’s a long haul around the solar system for this outer planet, taking 84 years to complete a full lap, and for the last few decades the poles weren’t pointed toward Earth. Since about 2015, scientists have had a better view and have been able to look deeper into the polar atmosphere.

Ingredients for a Cyclone

The cyclone on Uranus, compactly shaped with warm and dry air at its core, is much like those spotted by NASA’s Cassini at Saturn. With the new findings, cyclones (which rotate in the same direction their planet rotates) or anti-cyclones (which rotate in the opposite direction) have now been identified at the poles on every planet in our solar system except for Mercury, which has no substantial atmosphere.

But unlike hurricanes on Earth, cyclones on Uranus and Saturn aren’t formed over water (neither planet is known to have liquid water), and they don’t drift; they’re locked at the poles. Researchers will be watching closely to see how this newly discovered Uranus cyclone evolves in the coming years.

“Does the warm core we observed represent the same high-speed circulation seen by Voyager?” Akins asked. “Or are there stacked cyclones in Uranus’ atmosphere? The fact that we’re still finding out such simple things about how Uranus’ atmosphere works really gets me excited to find out more about this mysterious planet.”

The National Academies’ 2023 Planetary Science and Astrobiology Decadal Survey prioritized exploring Uranus. In preparation for such a mission, planetary scientists are focused on bolstering their knowledge about the mysterious ice giant’s system.

Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-6215
gretchen.p.mccartney@jpl.nasa.gov 

Karen Fox / Alana Johnson
NASA Headquarters, Washington
301-286-6284 / 202-358-1501
karen.c.fox@nasa.gov / alana.r.johnson@nasa.gov

Editor: Tony Greicius

Source: NASA/Uranus

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Astronomers Find Potentially Volcano-Covered Earth-Size World

Astronomers Find Potentially Volcano-Covered Earth-Size World
Credit: NASA’s Goddard Space Flight Center/Chris Smith (KRBwyle)

Download high-resolution video and images from NASA’s Scientific Visualization Studio 

Cambridge, MA--Astronomers have discovered an Earth-size exoplanet, a world beyond the solar system, that may be carpeted with volcanoes and could potentially support life. Called LP 791-18d, the planet could undergo volcanic outbursts as often as Jupiter's moon Io, the most volcanically active body in the solar system.

The planet was first reported in Nature and the discovery was made possible in part due to ground-based observations made by the Center for Astrophysics | Harvard & Smithsonian.

LP 791-18d orbits a small red dwarf star about 90 light-years away in a southern constellation called Crater. The team behind the discovery estimates it is only slightly larger and more massive than Earth. It is tidally locked, which means the same side constantly faces its star. The side facing the star would probably be too hot for liquid water to exist on the surface, but the team suspects that the amount of volcanic activity potentially taking place all over the planet could sustain an atmosphere. These conditions may allow water to condense on the dark side of the planet.

Discovery of the planet was made possible through a combination of space-based and ground-based observations. The researchers discovered and studied the planet using data from NASA's Transiting Exoplanet Survey Satellite (TESS) and retired Spitzer Space Telescope, as well as a suite of ground-based observatories organized by Collins.

The team initially estimated the planet's mass by measuring tiny differences in the time it takes the planet to orbit its host star from one orbit to the next, which are caused by the gravitational tug of the other planets in the system.

The planet's volcanic activity might arise from other planets in the same system. Before the discovery of LP 791-18d, astronomers already knew about two other worlds in the system, including LP 791-18c. The outer planet, c, is much larger and more massive than planet d.

During each orbit, planets d and c pass very close to each other. During each close pass, the more massive planet c produces a gravitational tug on the newly discovered planet d, making its orbit somewhat elliptical. On this elliptical path, planet d deforms slightly more every time it goes around the star. These deformations can create enough internal friction to substantially heat the planet's interior and produce volcanic activity at its surface. Jupiter and some of its moons affect Io in a similar way.

Planet d sits on the inner edge of the habitable zone, the traditional range of distances from a star where scientists hypothesize liquid water could exist on a planet's surface. If the planet is as geologically active as the research team suspects, it could maintain an atmosphere. Temperatures could drop enough on the planet's night side for water to condense on the surface.

Researchers have already received approval to study planet c using the recently launched James Webb Space Telescope, and the team thinks planet d is also an exceptional candidate for atmospheric studies by the mission.

"A big question in astrobiology, the field that broadly studies the origins of life on Earth and beyond, is if tectonic or volcanic activity is necessary for life," said co-author Jessie Christiansen, a research scientist at NASA's Exoplanet Science Institute at the California Institute of Technology (Caltech). "In addition to potentially providing an atmosphere, these processes could churn up materials that would otherwise sink down and get trapped in the crust, including those we think are important for life, like carbon."

"This discovery is just a first step," Collins said. "With the potential to continue studying this planet with the James Webb Space Telescope, we will be able to fine-tune our observations and learn more about the planet's likely volcanically fueled atmosphere. Future discoveries will help us understand how the ingredients of life might have come to be on worlds other than our own."

Other members of the research team from the CfA include David Charbonneau, Ryan Cloutier, David W. Latham, and Samuel N. Quinn.

TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California's Silicon Valley; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes and observatories worldwide participate in the mission.

Spitzer's observations of the system where LP 791-18d resides were among the last the satellite collected before it was decommissioned in January 2020. The entire body of scientific data collected by Spitzer during its lifetime is available to the public via the Spitzer data archive, housed at the Infrared Science Archive at IPAC at Caltech in Pasadena, California. NASA's Jet Propulsion Laboratory, a division of Caltech, managed Spitzer mission operations for the agency’s Science Mission Directorate in Washington. Science operations were conducted at the Spitzer Science Center at IPAC at Caltech. Spacecraft operations were based at Lockheed Martin Space in Littleton, Colorado.

About the Center for Astrophysics | Harvard & Smithsonian

The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity's greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.

Media Contact:

Peter Edmonds
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Center for Astrophysics | Harvard & Smithsonian
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pedmonds@cfa.harvard.edu

Source: Harvard-Smithsonian Center for Astrophysics (CfA)/News

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eROSITA sees changes in the most powerful quasar

Artist’s impression of a quasar
Credit: NOIRLab/NSF/AURA/J. da Silva

Researchers have observed the X-ray emission of the most luminous quasar seen in the last 9 billion years of cosmic history. Significant changes in the quasar’s emission give a new perspective on the inner workings of quasars and how they interact with their environment. The study was led by Dr Elias Kammoun, a postdoctoral researcher at the Research Institute in Astrophysics and Planetology (IRAP), and Zsofi Igo, a PhD candidate at the Max Planck Institute for Extraterrestrial Physics (MPE).

Hosted by a galaxy 9.6 billion light years away from the Earth, between the constellations of Centaurus and Hydra, the quasar known as SMSS J114447.77-430859.3, or J1144 for short, is extremely powerful. Shining 100,000 billion times brighter than the Sun, J1144 is much closer to Earth than other sources of the same luminosity, allowing astronomers to gain insight into the black hole powering the quasar and its surrounding environment.

Quasars are among the brightest and most distant objects in the known universe, powered by the fall of gas into a supermassive black hole. They can be described as active galactic nuclei (AGN) of very high luminosity that emit vast amounts of electromagnetic radiation; observable in radio, infrared, visible, ultraviolet and X-ray wavelengths. J1144 was initially observed in visible wavelengths in 2022 by the SkyMapper Southern Survey (SMSS).

For this study, researchers combined observations from several observatories in orbit around the Earth: the eROSITA instrument on board the Spectrum-Roentgen-Gamma (SRG) observatory, the ESA XMM-Newton observatory, NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), and NASA’s Neil Gehrels Swift observatory. eROSITA detected the source during the first five sky scans between 2020 and 2022. “eROSITA is not only a fantastic instrument to discover such rare bright quasars, but also to monitor their variability by repeatedly scanning their X-ray emission every six months,” says author Zsofi Igo. “It will be vital to further our knowledge of accretion physics.”

The team used the data from eROSITA and the other observatories to measure the temperature of the X-rays being emitted from the quasar. They found this temperature to be around 350 million Kelvin, more than 60,000 times the temperature at the surface of the Sun. The team also found that the mass of the black hole at the quasar’s centre is around 10 billion times the mass of the Sun, and the rate at which it is growing to be of the order of 100 solar masses per year.

Further information was revealed by studying how the quasar properties change over time. For example, eROSITA found J1144 to be variable in its brightness over timescales of a year, but interestingly showed little variation in the shape of its energy spectrum during this period. There was also variability detected on a timescale of a few days, which is not usually seen in quasars with black holes as large as the one residing in J1144. Additionally, the observations showed that while a portion of the gas is swallowed by the black hole, some gas is ejected in the form of extremely powerful winds, releasing large amounts of energy into the host galaxy.

“Similar quasars are usually found at much larger distances, so they appear much fainter, and we see them as they were when the Universe was only 2-3 billion years old,” says Dr. Kammoun, lead author of the paper. “J1144 is a very rare source as it is so luminous and much closer to Earth, giving us a unique glimpse of what such powerful quasars look like.”

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Contacts:

Zsofi Igo
phd student
+49 89 30000
zigo@mpe.mpg.de

Andrea Merloni
Senior Scientist
+49 89 30000-3893 +49 89 30000-3569
am@mpe.mpg.de

Original publication:

E. S. Kammoun, Z. Igo, J. M. Miller, et al.
The first X-ray look at SMSS J114447.77-430859.3: the most luminous quasar in the last 9 Gyr
Monthly Notices of the Royal Astronomical Society, stad952
DOI

More Information:

eROSITA
eROSITA webpages at MPE

Source: Max Planck Institute for Extraterrestrial Physics

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A Potential New Character in the Saga of HD 163296

This image shows the dust (pink) and carbon monoxide gas (blue) making up HD 163296's disk.
Credit: ALMA (ESO/NAOJ/NRAO); A. Isella; B. Saxton (NRAO/AUI/NSF)

Title: A Gap-Sharing Planet Pair Shaping the Crescent in HD 163296: a Disk Sculpted by a Resonant Chain
Authors: Juan Garrido-Deutelmoser et al.
First Author’s Institution: Pontifical Catholic University of Chile and the Millennium Nucleus for Planet Formation
Status: Published in ApJL

Figure 1: The observed structure of the disk around HD 163296, as reported in Isella et al. (2018). The crescent-shaped region is visible at the bottom left of the inner gap, as indicated by the white box and as shown in the zoomed-in image (a). It appears to be a cloud of gas and dust within the gap, distinct from the overdense ring around it. Credit: Adapted from Isella et al. 2018

An extra protoplanet might be lurking in the dust around a nearby star.

The pre-main-sequence star HD 163296 plays host to an extensive circumstellar disk, with gas reaching out beyond 500 astronomical units (au). Observations of this disk have revealed it to be quite the playground for the young planets forming within — and these authors claim there are more planets than previously thought.

HD 163926’s disk has a series of rings — bumps and dips in surface brightness, corresponding to over- and under-densities of material at different distances from the host star (Figure 1). Observations of this sort of ringed structure have become common fare since the advent of high-precision millimeter imaging in the last 15 years. These rings imply the presence of protoplanets or other large substellar bodies, which can clear out gaps through their growth and alter what would otherwise be a smooth(er) profile.

Trying to figure out the exact setup of bodies that gives a disk its observed structure is an interesting problem — and in the case of HD 163296, it’s a problem that has proven a bit tricky.

It only took low-resolution images of this particular disk (like those taken with the Hubble Space Telescope at the turn of the century) for Grady et al. to suggest that a giant planet might be present in the outer reaches of this system. Jumping ahead to 2018, Teague et al. used rotation curves of observed gas to claim that there were likely two planets out there — both roughly as massive as Jupiter, at 87 and 113 au. Just a few months later, high-precision observations by the Atacama Large Millimeter/submillimeter Array (ALMA) revealed that the disk contains not just a series of gaps but also an intriguing substructure within the innermost one.

Today’s article focuses on this innermost gap, which extends from 38 to 62 au, and the crescent-shaped region near the edge of it that appears to have more material than it should (Figure 1).

The standard idea that gaps form along the orbit of a protoplanet doesn’t allow for this sort of uneven, crescent-shaped structure; the protoplanet should clear the material evenly all the way around the orbit, but it seems to have missed a spot. Modeling this gap, and the substructure within, would complete our current understanding of the HD 163296 system.

Luckily, the crescent has a fairly straightforward explanation. To understand it, though, we need to talk about Lagrange points.

Figure 2: A diagram of the Lagrange points of a star–planet system. Smaller objects, like asteroids and dust, often accumulate at L4 and L5 due to the long-term stability of these points. Credit: Mark Dodici

If you’ve taken a class on classical mechanics, you might remember that Lagrange points are sort of like gravitational islands. For any pair of massive bodies (say, a star with a protoplanet), there are five points where the gravitational forces of the bodies balance nearly perfectly to keep much-less-massive things at those points, fixed relative to the more massive bodies. Two of these (L4 and L5) are stable against small displacements, meaning smaller things like asteroids and dust often accumulate at or around these two points. L4 lies almost exactly on the orbit of the less-massive body, in front of it by ~60 degrees. L5 trails behind the less-massive body by the same angle (Figure 2).

In the HD 163296 system, this crescent-shaped region with extra dust and gas could perhaps be explained as a build-up of material in the L4 or L5 of some massive protoplanet, which had otherwise cleared out the gap. In 2021, Rodenkirch et al. simulated the interactions between a gap-clearing planet and the dust around it, and they showed that this could work: a Jupiter-mass planet orbiting the star at 48 AU would both open up the observed gap and trap a significant amount of dust at its trailing L5.

And so the system was solved. The crescent-shaped substructure in HD 163296’s disk was the result of a Jupiter-mass planet. The other gaps were caused by two other planets farther out.

And yet, today’s featured article came out just recently. Why?

It turns out there were two problems with the Lagrange point idea. First, the crescent is centered at a radial distance of 55 au, which requires a lot of dynamical hoop-jumping-through to make sense for a Jupiter-mass planet at 48 au. Second, a Jupiter-mass planet would open up a deep gap in the gaseous disk. Less than a year after the first submission of Rodenkirch et al., observations by Zhang et al. of the disk’s carbon monoxide (CO) surface density — a great tracer for the overall gas density throughout a disk — showed that the gas gap between 38 and 62 au is ten times shallower than it would be if it were carved by a Jupiter-mass planet.

Enter Garrido-Deutelmoser et al. Last year, they studied the effects of having two planets in the same gap in a protoplanetary disk. Through hydrodynamical simulations, they showed that if two sub-Jupiter-mass planets are close enough to each other, their gravitational interactions would create relatively stable “vortices” at L4 and L5 of either of the planets. These vortices could maintain over-densities of dust and gas for thousands of orbits — plenty of time for us to have observed one of them.

In today’s featured article, Garrido-Deutelmoser (and a slightly different) et al. applied this concept to HD 163296. They set up simulations of the system mostly matching those of Rodenkirch et al., with the two proposed outer planets and a smooth disk of gas and dust. But in place of one Jupiter-mass planet at 48 au, they implanted two planets with a few times the mass of Neptune in that region. Since these two combine for a much smaller mass than Jupiter, they would create a much shallower gap in the gas density profile — ideally matching that found in Zhang et al.

Figure 3: The radial gas density profile of HD 163296. Dark Purple: observed profile from Zhang et al. (2021). Magenta: simulated profile with one planet opening the 38–62 AU gap (the Rodenkirch et al. (2021) model). Orange: simulated profile with two planets opening said gap (this paper). Neither model fits well beyond ~85 AU, but the two-planet model matches the CO gap depth much more closely up to that point. Credit: Garrido-Deutelmoser et al. 2023

Figure 4: The observed structure of the disk around HD 163296 (left) and the faux-observed structure from this simulation (right). The proposed locations of the four protoplanets are labeled on the left panel. While the simulated disk isn’t a perfect replica, it recreates most of the important details of the interior portions of the observed disk. Credit: Garrido-Deutelmoser et al. 2023

Through trial and error, they found that planets at 46 and 54 au could, in fact, carve out the appropriate density profile for this gap in both dust and gas (Figure 3) over the course of a half-million-year simulation. And in line with expectations from their previous work, material congregated at L5 for the outer super-Neptune (though they note that this ebbed and flowed over time). They do point out that neither their model nor the Rodenkirch et al. captured the density profile accurately beyond ~85 au, which they explain might be an issue with gas dynamics beyond that point. Regardless, their two-planet model for the gap of interest seems to be a winner.

They close the article with a final proposition, suggesting where in their orbits one might find each of the protoplanets, based largely on the fact that they seem to be close to a mean motion resonance chain — that is, they seem to have orbital periods that are roughly integer multiples of each other. Using a relationship for the orbital angles of objects in such a resonance, along with the location of the crescent and observations of kinematic features in the gas, the authors infer the precise locations of each of the protoplanets within the disk (Figure 4).

In the end, this might provide one final check for this finicky system. If the protoplanets are where they say they are, we’re golden. If not, the saga of HD 163296 will go on.

Original Astrobite edited by Lucie Rowland and Zili Shen.

About the author, Mark Dodici:

Mark is a first-year PhD student in astronomy and astrophysics at the University of Toronto. His space-based interests include planetary systems, from their births to their varied deaths, as well as the dynamics of just about anything else. His Earth-based interests include coffee, photography, and a little bit of singing now and again. You can follow him on Twitter @MarkDodici.

Source: American Astronomical Society/AAS Nova

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NASA's Hubble Hunts for Intermediate-Sized Black Hole Close to Home

A Hubble Space Telescope image of the globular star cluster, Messier 4. The cluster is a dense collection of several hundred thousand stars. Astronomers suspect that an intermediate-mass black hole, weighing as much as 800 times the mass of our Sun, is lurking, unseen, at its core. Credits: Image: ESA/Hubble, NASA. Science: NASA, ESA, Eduardo Vitral (STScI)

Release Images | Release Videos

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Astronomers using NASA's Hubble Space Telescope have come up with what they say is some of their best evidence yet for the presence of a rare class of "intermediate-sized" black hole that may be lurking in the heart of the closest globular star cluster to Earth, located 6,000 light-years away.

Like intense gravitational potholes in the fabric of space, virtually all black holes seem to come in two sizes: small and humongous. It's estimated that our galaxy is littered with 100 million small black holes (several times the mass of our Sun) created from exploded stars. The universe at large is flooded with supermassive black holes, weighing millions or billions of times our Sun’s mass and found in the centers of galaxies.

A long-sought missing link is an intermediate-mass black hole, weighing in somewhere between 100 and 100,000 solar masses. How would they form, where would they hang out, and why do they seem to be so rare?

Astronomers have identified other possible intermediate-mass black holes through a variety of observational techniques. Two of the best candidates — 3XMM J215022.4−055108, which Hubble helped discover in 2020, and HLX-1, identified in 2009, reside in dense star clusters in the outskirts of other galaxies. Each of these possible black holes has the mass of tens of thousands of suns, and may have once been at the centers of dwarf galaxies. NASA’s Chandra X-ray observatory has also helped make many possible intermediate black hole discoveries, including a large sample in 2018.

Looking much closer to home, there have been a number of suspected intermediate-mass black holes detected in dense globular star clusters orbiting our Milky Way galaxy. For example, in 2008, Hubble astronomers announced the suspected presence of an intermediate-mass black hole in the globular cluster Omega Centauri. For a number of reasons, including the need for more data, these and other intermediate-mass black hole findings still remain inconclusive and do not rule out alternative theories.

Hubble's unique capabilities have now been used to zero in on the core of the globular star cluster Messier 4 (M4) to go black-hole hunting with higher precision than in previous searches. "You can't do this kind of science without Hubble," said Eduardo Vitral of the Space Telescope Science Institute in Baltimore, Maryland, lead author on a paper to be published in the Monthly Notices of the Royal Astronomical Society.

Vitral’s team has detected a possible intermediate-mass black hole of roughly 800 solar masses. The suspected object can't be seen, but its mass is calculated by studying the motion of stars caught in its gravitational field, like bees swarming around a hive. Measuring their motion takes time, and a lot of precision. This is where Hubble accomplishes what no other present-day telescope can do. Astronomers looked at 12 years' worth of M4 observations from Hubble and resolved pinpoint stars.

His team estimates that the black hole in M4 could be as much as 800 times our Sun's mass. Hubble's data tend to rule out alternative theories for this object, such as a compact central cluster of unresolved stellar remnants like neutron stars, or smaller black holes swirling around each other.

"We have good confidence that we have a very tiny region with a lot of concentrated mass. It's about three times smaller than the densest dark mass that we had found before in other globular clusters," said Vitral. "The region is more compact than what we can reproduce with numerical simulations when we take into account a collection of black holes, neutron stars, and white dwarfs segregated at the cluster's center. They are not able to form such a compact concentration of mass."

A grouping of close-knit objects would be dynamically unstable. If the object isn't a single intermediate-mass black hole, it would require an estimated 40 smaller black holes crammed into a space only one-tenth of a light-year across to produce the observed stellar motions. The consequences are that they would merge and/or be ejected in a game of interstellar pinball.

"We measure the motions of stars and their positions, and we apply physical models that try to reproduce these motions. We end up with a measurement of a dark mass extension in the cluster's center," said Vitral. "The closer to the central mass, more randomly the stars are moving. And, the greater the central mass, the faster these stellar velocities."

Because intermediate-mass black holes in globular clusters have been so elusive, Vitral cautions, "While we cannot completely affirm that it is a central point of gravity, we can show that it is very small. It's too tiny for us to be able to explain other than it being a single black hole. Alternatively, there might be a stellar mechanism we simply don't know about, at least within current physics."

The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

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About This Release

Credits:

Media Contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Science Contact:

Eduardo Vitral
Space Telescope Science Institute, Baltimore, Maryland
Paris Institute of Astrophysics, Paris, France

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents

• Science Paper: The science paper by Eduardo Vitral et al., PDF (2.06 MB)
• NASA's Hubble Portal
• ESA/Hubble's Release
• ESA's Release

Source: HubbleSite/News

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A jellyfish galaxy adrift

A spiral galaxy. It is large in the centre with a lot of detail visible. The core glows brightly and is surrounded by concentric rings of dark and light dust. The spiral arms are thick and puffy with grey dust and glowing blue areas of star formation. They wrap around the galaxy to form a ring. Part of the arm is drawn out into a dark thread above the galaxy, and dust from the arm trails off to the right. Hi-res image

The jellyfish galaxy JW39 hangs serenely in this image from the NASA/ESA Hubble Space Telescope. This galaxy lies over 900 million light-years away in the constellation Coma Berenices, and is one of several jellyfish galaxies that Hubble has been studying over the past two years.

Despite this jellyfish galaxy’s serene appearance, it is adrift in a ferociously hostile environment; a galaxy cluster. Compared to their more isolated counterparts, the galaxies in galaxy clusters are often distorted by the gravitational pull of larger neighbours, which can twist galaxies into a variety of weird and wonderful shapes. If that was not enough, the space between galaxies in a cluster is also pervaded with a searingly hot plasma known as the intracluster medium. While this plasma is extremely tenuous, galaxies moving through it experience it almost like swimmers fighting against a current, and this interaction can strip galaxies of their star-forming gas.

This interaction between the intracluster medium and the galaxies is called ram-pressure stripping, and is the process responsible for the trailing tendrils of this jellyfish galaxy. As JW39 has moved through the cluster the pressure of the intracluster medium has stripped away gas and dust into long trailing ribbons of star formation that now stretch away from the disc of the galaxy.

Astronomers using Hubble’s Wide Field Camera 3 studied these trailing tendrils in detail, as they are a particularly extreme environment for star formation. Surprisingly, they found that star formation in the ‘tentacles’ of jellyfish galaxies was not noticeably different from star formation in the galaxy disc.

Links

• First science paper in the Astrophysical Journal
• Second science paper in the Astrophysical Journal
• Pan: A jellyfish galaxy adrift

Source: ESA/Hubble/potw

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Scrutinising a star-studded cluster

NGC 6325

The dense cluster of bright stars. The core of the cluster is to the left and has a distinct group of blue stars. Surrounding the core are a multitude of stars in warmer colours. These stars are very numerous near the core and become more and more sparse, and more small and distant, out to the sides of the image. A few larger stars also stand in the foreground near the edges of the image. Credit: ESA/Hubble & NASA, E. Noyola, R. Cohen. Hi-res image

The densely packed globular cluster NGC 6325 glistens in this image from the NASA/ESA Hubble Space Telescope. This concentrated group of stars lies around 26 000 light years from Earth in the constellation Ophiuchus.

Globular clusters like NGC 6325 are tightly bound collections of stars with anywhere from tens of thousands to millions of members. They can be found in all types of galaxies, and act as natural laboratories for astronomers studying star formation. This is because the constituent stars of globular clusters tend to form at roughly the same time and with similar initial composition, meaning that astronomers can use them to fine-tune their theories of how stars evolve.

Astronomers inspected this particular cluster not to understand star formation, but to search for a hidden monster. Though it might look peaceful, astronomers suspect this cluster could contain an intermediate-mass black hole that is subtly affecting the motion of surrounding stars. Previous research found that the distribution of stars in some highly concentrated globular clusters — those with stars packed relatively tightly together — was slightly different from what astronomers expected.

This discrepancy suggested that at least some of these densely packed globular clusters — including perhaps NGC 6325 — could have a black hole lurking at the centre. To explore this hypothesis further, astronomers turned to Hubble’s Wide Field Camera 3 to observe a larger sample of densely populated globular clusters, which included this star-studded image of NGC 6325. Additional data from Hubble’s Advanced Camera for Surveys were also incorporated into this image.

Source: ESA/Hubble/potw

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First Detection of Radio Waves from a Type Ia Supernova

Artist's rendition of SN 2020eyj, a white dwarf star that went supernova after pulling material from a helium companion star. Credit: W. M. Keck Observatory/Adam Makarenko

Maunakea, Hawaiʻi – A team of astronomers led by Stockholm University has discovered an unusual Type Ia supernova – or thermonuclear supernova – called SN 2020eyj. Not only did they make the first detection of such a supernova in radio waves, follow-up observations from W. M. Keck Observatory on Maunakea, Hawaiʻi Island also showed strong emission lines of helium.

This marks the first confirmed Type Ia supernova triggered by a white dwarf star that pulled material from a companion star with an outer layer consisting primarily of helium; normally, in the rare cases where the material stripped from the outer layers of the donor star could be detected in spectra, this was mostly hydrogen.

Type Ia supernovae are important for astronomers since they are used to measure the expansion of the universe. However, the origin of these explosions has remained an open question. While it is established that the explosion is caused by a compact white dwarf star that somehow accretes too much matter from a companion star, the exact process and the nature of the progenitor is not known.

The new discovery of supernova SN 2020eyj is evidence the companion star was a helium star that had lost much of its material just prior to the explosion of the white dwarf.

The study, which includes data from Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS), is published in today’s issue of the journal Nature.

First Detection of Radio Waves from a Type Ia Supernova from Keck Observatory on Vimeo.

Artist’s impression of SN2020eyj, a double star system with a compact white dwarf star accreting matter from a helium-rich donor companion, surrounded by dense and dusty circumstellar material. It was the interaction of the exploded star and the material left over from this companion that gave rise to the strong radio signal and the conspicuous helium lines in the optical spectra of SN 2020eyj. Credit: W. M. Keck Observatory/Adam Makarenko

“Once we saw the signatures of strong interaction with the material from the companion, we tried to also detect it in radio emission,” says Erik Kool, a postdoc at Stockholm University’s Department of Astronomy and lead author of the paper. “The detection in radio is the first one of a Type Ia supernova – something astronomers have tried to do for decades.”

Supernova 2020eyj was first spotted by the Zwicky Transient Facility at Palomar Observatory near San Diego where the Oskar Klein Centre at Stockholm University are members.

“The Nordic Optical Telescope on La Palma was fundamental for following up this supernova,” says Jesper Sollerman, a professor at Stockholm University’s Department of Astronomy and co-author of the paper. “As were spectra from the large Keck telescope in Hawaiʻi that immediately revealed the very unusual helium-dominated material around the exploded star.”

“This is clearly a very unusual Type Ia supernova, but still related to the ones we use to measure the expansion of the universe,” adds co-author Joel Johansson from the Department of Physics at Stockholm University. “While normal Type Ia supernovae appear to always explode with the same brightness, this supernova tells us that there are many different pathways to a white dwarf star explosion.”

Source: W.M.Keck Observatory/Science News

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About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

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About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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NASA’s Webb Finds Water, and a New Mystery, in Rare Main Belt Comet

Artist's Concept of Comet 238P/Read
Credits: Illustration: NASA, ESA

Comet 238P/Read (NIRCam Image)
Credits: Image: NASA, ESA, CSA, Mike Kelley (UMD)
Image Processing: Henry Hsieh (PSI), Alyssa Pagan (STScI)

Comet Spectra Comparison
Credits: Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI)

Release Images

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NASA’s James Webb Space Telescope has enabled another long-sought scientific breakthrough, this time for solar system scientists studying the origins of Earth’s abundant water. Using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, astronomers have confirmed gas – specifically water vapor – around a comet in the main asteroid belt for the first time, indicating that water ice from the primordial solar system can be preserved in that region. However, the successful detection of water comes with a new puzzle: unlike other comets, Comet 238P/Read had no detectable carbon dioxide.

“Our water-soaked world, teeming with life and unique in the universe as far as we know, is something of a mystery – we’re not sure how all this water got here,” said Stefanie Milam, Webb deputy project scientist for planetary science and a co-author on the study reporting the finding. “Understanding the history of water distribution in the solar system will help us to understand other planetary systems, and if they could be on their way to hosting an Earth-like planet,” she added.

Comet Read is a main belt comet – an object that resides in the main asteroid belt but which periodically displays a halo, or coma, and tail like a comet . Main belt comets themselves are a fairly new classification, and Comet Read was one of the original three comets used to establish the category. Before that, comets were understood to reside in the Kuiper Belt and Oort Cloud, beyond the orbit of Neptune, where their ices could be preserved farther from the Sun. Frozen material that vaporizes as they approach the Sun is what gives comets their distinctive coma and streaming tail, differentiating them from asteroids. Scientists have long speculated that water ice could be preserved in the warmer asteroid belt, inside the orbit of Jupiter, but definitive proof was elusive – until Webb.

“In the past, we’ve seen objects in the main belt with all the characteristics of comets, but only with this precise spectral data from Webb can we say yes, it’s definitely water ice that is creating that effect,” explained astronomer Michael Kelley of the University of Maryland, lead author of the study.

“With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early solar system can be preserved in the asteroid belt,” Kelley said.

The missing carbon dioxide was a bigger surprise. Typically, carbon dioxide makes up about 10 percent of the volatile material in a comet that can be easily vaporized by the Sun’s heat. The science team presents two possible explanations for the lack of carbon dioxide. One possibility is that Comet Read had carbon dioxide when it formed but has lost that because of warm temperatures.

“Being in the asteroid belt for a long time could do it – carbon dioxide vaporizes more easily than water ice, and could percolate out over billions of years,” Kelley said. Alternatively, he said, Comet Read may have formed in a particularly warm pocket of the solar system, where no carbon dioxide was available.

The next step is taking the research beyond Comet Read to see how other main belt comets compare, says astronomer Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), lead for Webb’s Guaranteed Time Observations for solar system objects and co-author of the study. “These objects in the asteroid belt are small and faint, and with Webb we can finally see what is going on with them and draw some conclusions. Do other main belt comets also lack carbon dioxide? Either way it will be exciting to find out,” Hammel said.

Co-author Milam imagines the possibilities of bringing the research even closer to home. “Now that Webb has confirmed there is water preserved as close as the asteroid belt, it would be fascinating to follow up on this discovery with a sample collection mission, and learn what else the main belt comets can tell us.”

The study is published in the journal Nature.

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About This Release

Credits:

Media Contact:

Leah Ramsay
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science:

Mike Kelley (UMD)

Permissions:Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents:

• The science paper by M. Kelley et al.
• The Planetary Science Institute press release

 

 Source: NASA's James Webb Space Telescope/News

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Direct Imaging of Gas Recycling around a Massive Galaxy in the Early Universe

Artistic impression of the gas cycle in the circumgalactic medium of a massive galaxy, as well as the setup of the main observations used in this work. The inset figures show the Keck telescope (bottom) used to acquire the data with the KCWI instrument (top), which is an integral field spectrograph and therefore obtains three-dimensional data-cubes (2 spatial dimensions + velocity). Such instruments are key in detecting large-scale diffuse gas, while simultaneously studying its kinematics. Copyright: Tsinghua University

Galaxies are the birthplace of most stars and black holes. However, scientists are still debating, how galaxies accrete the fuel to sustain their growth, and how they in turn pollute their environment with elements heavier than helium. An international team of astrophysicists has now directly observed the neighborhood of a massive galaxy in the early universe. They find that the gas all around the galaxy is enriched with heavy elements, which means it has been polluted by the galaxy itself and by embedded satellite galaxies. Furthermore, this gas is spiraling onto the massive galaxy, fueling further star formation.

According to the first models of galaxy formation, gas fell isotropically onto dark matter halos, was shock-heated to very high temperatures (millions of degrees), and subsequently cooled to form stars in the growing central galaxy. However, it is now clear that this so-called ‘hot-mode’ accretion accounts for only a small fraction of the fuel powering the violent star formation in massive galaxies in the early universe. Instead, cosmological hydrodynamical simulations indicate that a ‘cold-mode’ accretion (thousands of degrees) onto galaxies occurs along filaments. This accretion process is more efficient in transporting gas down to the galaxy, providing a natural mechanism to sustain the observed large star-formation rates.

In turn, stars pollute their surrounding environment with elements heavier than helium, globally referred to as “metals”. The most energetic phenomena (supernova explosions) are even able to generate galactic outflows, enriching the circumgalactic gas. Recent cosmological simulations indicate that this metal-enriched gas ejected by the galaxy could fall back, resulting in a further supply mechanism to sustain intense star-forming activity. Therefore, a massive galaxy will both recycle its metal-polluted gas and use pristine, inflowing gas. However, direct observational evidence for the presence of such recycled inflows had not been obtained so far.

An international team of astronomers has therefore targeted a massive system in the early universe, to get a first glimpse on how such galaxies accrete their gas. The chosen system, MAMMOTH-1, can be observed at an epoch corresponding to 11 billion years ago. It is a galaxy group embedded in large-scale cold circumgalactic gas, which shines bright in Lyman-alpha emission from hydrogen.

With data from the Keck Cosmic Web Imager (KCWI, Keck II telescope) and narrowband imaging from the Subaru telescope, the team detected circumgalactic line emission in hydrogen, helium, and carbon extending for 300 000 light years. An analysis of the line ratios allowed the team to obtain the gas properties throughout the halo. The results show that the circumgalactic gas has already been enriched to about solar metallicity, which is quite surprising at this early cosmic epoch.

Further, the KCWI data allowed the team to analyse the kinematics of the emitting gas in the observed region. A detailed comparison of the data with cosmological simulations developed at the Max Planck Institute for Astrophysics and with an analytical model can explain the observed velocity patterns, which are most likely due to recycled inflow gas. The kinematic model indicates that the gas accretion is occurring at a rate of about 700 solar masses per year, much more than the measured star-formation rate of the central galaxy (81 solar masses per year). The metal-enriched inflow could thus fully sustain the intense star formation in the massive galaxy. “Our observations give a first hint that recycled inflows might be an ubiquitous supply mechanism for massive star-forming galaxies in the early universe”, remarks Shiwu Zhang of Tsinghua University and first-author of the study.

MAMMOTH-1 with circumgalactic gas and satellite galaxies

This animation shows both the observation setup and the results of the analysis. The video starts with an artistic impression of the gas cycling around a massive galaxy as well as the data from the cosmological simulations (IllustrisTNG) developed at the Max Planck Institute for Astrophysics, which was used in the analysis. The light from this galaxy and its surroundings is collected by the KCWI instrument on the Keck II telescope. From this data, the scientists obtain velocity maps, with an example shown here for the Lyman-alpha emission from hydrogen. These data are used to constrain the gas flow depicted at the beginning.

In addition, the team also found that satellite galaxies in this galaxy group have the same motion as the circumgalactic gas, indicating that they are embedded in the inspiraling streams. Therefore, these satellite galaxies could interact with and pollute the circumgalactic gas. “This makes the galaxy-gas ecosystem even more complex, but also it makes more plausible that gas recycling is an important ingredient,” adds Zheng Cai of Tsinghua University and second-author of the study.

“We need a lot more sensitive observations of circumgalactic emission to give us more insights on the intricate ecosystem of galaxies”, points out Fabrizio Arrigoni Battaia, co-author and scientist at the Max Planck Institute for Astrophysics. “Our approach together with the upcoming exquisite datasets, such as from the MUSE/VLT, KCWI instruments, and JWST, allows us to directly study the circumgalactic gas in detail and thus better understand the physical processes governing the gas cycle around galaxies.”

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Contact:

Fabrizio Arrigoni Battaia
Scientific Staff
tel: 2288
arrigoni@mpa-garching.mpg.de

Original Publication:

S. Zhang, Z. Cai, D. Xu, R. Shimakawa, F. Arrigoni Battaia, et al.
Inspiraling streams of enriched gas observed around a massive galaxy 11 billion years ago
Science, 5 May 2023

Source: Max Planck Institute for Astrophysics/Press Releases

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Astronomers Witness Star Devouring Planet: Possible Preview of the Ultimate Fate of Earth

PR Image noirlab2311a

Artist Impression of a Star Devouring One of Its Planets

PR Image noirlab2311b

Infographic of Star Engulfing a Planet 

 

PR Image noirlab2311c

Infografía de una Estrella devorando un Planeta

 

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Videos

PR Video noirlab2311a

Astronomers Witness Star Devouring Planet: Possible Preview of the Ultimate Fate of Earth

PR Video noirlab2311b

Por primera vez astrónomos observan un planeta devorado por su estrella

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Gemini South captures first direct evidence of an exoplanet being swallowed by an ancient Sun-like star

Astronomers using the Gemini South telescope in Chile, operated by NSF’s NOIRLab, have observed the first evidence of a dying Sun-like star engulfing an exoplanet. The “smoking gun” of this event was seen in a long and low-energy outburst from the star — the telltale signature of a planet skimming along a star’s surface. This never-before-seen process may herald the ultimate fate of Earth when our own Sun nears the end of its life in about five billion years.

By studying countless stars at various stages of their evolution, astronomers have been able to piece together an understanding of the life cycle of stars and how they interact with their surrounding planetary systems as they age. This research confirms that when a Sun-like star nears the end of its life, it expands anywhere from 100 to 1000 times its original size, eventually engulfing the system’s inner planets. Such events are estimated to occur only a few times each year across the entire Milky Way. Though past observations have confirmed the aftermath of planetary engulfments [1], astronomers have never caught one in the act, until now.

With the power of the Gemini South Adaptive Optics Imager (GSAOI) on Gemini South, one half of the International Gemini Observatory, operated by NSF’s NOIRLab, [2] astronomers have observed the first direct evidence of a dying star expanding to engulf one of its planets. Evidence for this event was found in a telltale “long and low-energy” outburst from a star in the Milky Way about 13,000 light-years from Earth. This event, the devouring of a planet by an engorged star, likely presages the ultimate fate of Mercury, Venus, and Earth when our Sun begins its death throes in about five billion years.

“These observations provide a new perspective on finding and studying the billions of stars in our Milky Way that have already consumed their planets,” says Ryan Lau, NOIRLab astronomer and co-author on this study, which is published in the journal Nature.

For most of its life, a Sun-like star fuses hydrogen into helium in its hot, dense core, which allows the star to push back against the crushing weight of its outer layers. When hydrogen in the core runs out, the star begins fusing helium into carbon, and hydrogen fusion migrates to the star’s outer layers, causing them to expand, and changing the Sun-like star into a red giant.

Such a transformation, however, is bad news for any inner-system planets. When the star's surface eventually expands to engulf one of its planets, their interaction would trigger a spectacular outburst of energy and material. This process would also put the brakes on the planet's orbital velocity, causing it to plunge into the star.

The first hints of this event were uncovered by optical images from the Zwicky Transient Facility. Archival infrared coverage from NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), which is able to peer into dusty environments in search of outbursts and other transient events, then confirmed the engulfment event, named ZTF SLRN-2020. “Our team’s custom reanalysis of all-sky infrared maps from NEOWISE exemplifies the vast discovery potential of archival survey data sets,” said NOIRLab astronomer Aaron Meisner, another co-author on the paper.

Distinguishing a planetary-engulfment outburst from other types of outbursts, such as solar-flare-type events and coronal-mass ejections, is difficult and requires high-resolution observations to pinpoint the location of an outburst and long-term measurements of its brightness without contamination from nearby stars.

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More Information

Gemini South provided these essential data thanks to its adaptive-optics capabilities.

“Gemini South continues to expand our understanding of the Universe and these new observations support predictions for the future of our own planet,” said NSF Gemini Observatory program director Martin Still. “This discovery is a wonderful example of the feats we can accomplish when we combine world-class telescope operations and cutting-edge scientific collaboration.”

“With these revolutionary new optical and infrared surveys, we are now witnessing such events happen in real time in our own Milky Way — a testament to our almost certain future as a planet,” said Kishalay De, an astronomer at the Massachusetts Institute of Technology and lead author on the paper.

The outburst from the engulfment lasted approximately 100 days and the characteristics of its lightcurve, as well as the ejected material, gave astronomers insight into the mass of the star and that of its engulfed planet. The ejected material consisted of about 33 Earth masses of hydrogen and about 0.33 Earth masses of dust. “That's more star- and planet-forming material being recycled, or burped out, into the interstellar medium thanks to the star eating the planet,” said Lau. From this analysis, the team estimated that the progenitor star is about 0.8−1.5 times the mass of our Sun and the engulfed planet was 1−10 times the mass of Jupiter.

Now that the signatures of a planetary engulfment have been identified for the first time, astronomers have improved metrics they can use to search for similar events happening elsewhere in the cosmos. This will be especially important when Vera C. Rubin Observatory comes on line in 2025. For instance, the observed effects of chemical pollution on the remnant star when seen elsewhere can hint that an engulfment has taken place. The interpretation of this event also provides evidence for a missing link in our understanding of the evolution and final fates of planetary systems, including our own.

“I think there's something pretty remarkable about these results that speaks to the transience of our existence,” says Lau. “After the billions of years that span the lifetime of our Solar System, our own end stages will likely conclude in a final flash that lasts only a few months.”

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Links

• Research paper: “An infrared transient from a star engulfing a planet”
• Photos of the Gemini South telescope
• Videos of the Gemini South telescope

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Contacts:

Kishalay De
MIT Kavli Institute Postdoctoral Fellow
Email: kde1@mit.edu
Charles Blue
NSF’s NOIRLab
Tel: +1 202 236 6324
Email: charles.blue@noirlab.edu

Josie Fenske
NSF’s NOIRLab
Email: josie.fenske@noirlab.edu

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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