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The James Webb Space Telescope has spotted the earliest known galaxy to abruptly stop forming stars.
The galaxy, called GS-9209, quenched its star formation more than 12.5 billion years ago, researchers report January 26 at arXiv.org. That’s only a little more than a billion years after the Big Bang. Its existence reveals new details about how galaxies live and die across cosmic time.
“It’s a remarkable discovery,” says astronomer Mauro Giavalisco of the University of Massachusetts Amherst, who was not involved in the new study. “We really want to know when the conditions are ripe to make quenching a widespread phenomenon in the universe.” This study shows that at least some galaxies quenched when the universe was young.
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GS-9209 was first noticed in the early 2000s. In the last few years, observations with ground-based telescopes identified it as a possible quenched galaxy, based on the wavelengths of light it emits. But Earth’s atmosphere absorbs the infrared wavelengths that could confirm the galaxy’s distance and that its star-forming days were behind it, so it was impossible to know for sure.
So astrophysicist Adam Carnall and colleagues turned to the James Webb Space Telescope, or JWST. The observatory is very sensitive to infrared light, and it’s above the blockade of Earth’s atmosphere (SN: 1/24/22). “This is why JWST exists,” says Carnall, of the University of Edinburgh. JWST also has much greater sensitivity than earlier telescopes, letting it see fainter, more distant galaxies. While the largest telescopes on the ground could maybe see GS-9209 in detail after a month of observing, “JWST can pick this stuff up in a few hours.”
Using JWST observations, Carnall and colleagues found that GS-9209 formed most of its stars during a 200-million-year period, starting about 600 million years after the Big Bang. In that cosmically brief moment, it built about 40 billion solar masses’ worth of stars, about the same as the Milky Way has.
That quick construction suggests that GS-9209 formed from a massive cloud of gas and dust collapsing and igniting stars all at once, Carnall says. “It’s pretty clear that the vast majority of the stars that are currently there formed in this big burst.”
Astronomers used to think this mode of galaxy formation, called monolithic collapse, was the way that most galaxies formed. But the idea has fallen out of favor, replaced by the notion that large galaxies form from the slow merging of many smaller ones (SN: 5/17/21).
“Now it looks like, at least for this object, monolithic collapse is what happened,” Carnall says. “This is probably the clearest proof yet that that kind of galaxy evolution happens.”
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As to what caused the galaxy’s star-forming frenzy to suddenly stop, the culprit appears to be an actively feeding black hole. The JWST observations detected extra emission of infrared light associated with a rapidly swirling mass of energized hydrogen, which is a sign of an accreting black hole. The black hole appears to be up to a billion times the mass of the sun.
To reach that mass in less than a billion years after the birth of the universe, the black hole must have been feeding even faster earlier on in its life, Carnall says (SN: 3/16/18). As it gorged, it would have collected a glowing disk of white-hot gas and dust around it.
“If you have all that radiation spewing out of the black hole, any gas that’s nearby is going to be heated up to an incredible extent, which stops it from falling into stars,” Carnall says.
More observations with future telescopes, like the planned Extremely Large Telescope in Chile, could help figure out more details about how the galaxy was snuffed out. More
Mysterious cosmic bubbles are being seen in a new light. For the first time, scientists have observed visible light from the Fermi bubbles, enormous blobs of gas that sandwich the plane of the Milky Way galaxy. The newly spotted glow was emitted by hydrogen gas that was electrically charged, or ionized, within the bubbles. Astronomer […] More
Fourteen pinpricks of light on a gamma-ray map of the sky could fit the bill for antistars, stars made of antimatter, a new study suggests.
These antistar candidates seem to give off the kind of gamma rays that are produced when antimatter — matter’s oppositely charged counterpart — meets normal matter and annihilates. This could happen on the surfaces of antistars as their gravity draws in normal matter from interstellar space, researchers report online April 20 in Physical Review D.
“If, by any chance, one can prove the existence of the antistars … that would be a major blow for the standard cosmological model,” says Pierre Salati, a theoretical astrophysicist at the Annecy-le-Vieux Laboratory of Theoretical Physics in France not involved in the work. It “would really imply a significant change in our understanding of what happened in the early universe.”
It’s generally thought that although the universe was born with equal amounts of matter and antimatter, the modern universe contains almost no antimatter (SN: 3/24/20). Physicists typically think that as the universe evolved, some process led to matter particles vastly outnumbering their antimatter alter egos (SN: 11/25/19). But an instrument on the International Space Station recently cast doubt on this assumption by detecting hints of a few antihelium nuclei. If those observations are confirmed, such stray antimatter could have been shed by antistars.
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Intrigued by the possibility that some of the universe’s antimatter may have survived in the form of stars, a team of researchers examined 10 years of observations from the Fermi Gamma-ray Space Telescope. Among nearly 5,800 gamma-ray sources in the catalog, 14 points of light gave off gamma rays with energies expected of matter-antimatter annihilation, but did not look like any other known type of gamma-ray source, such as a pulsar or black hole.
Based on the number of observed candidates and the sensitivity of the Fermi telescope, the team calculated how many antistars could exist in the solar neighborhood. If antistars existed within the plane of the Milky Way, where they could accrete lots of gas and dust made of ordinary matter, they could emit lots of gamma rays and be easy to spot. As a result, the handful of detected candidates would imply that only one antistar exists for every 400,000 normal stars.
If, on the other hand, antistars tended to exist outside the plane of the galaxy, they would have much less opportunity to accrete normal matter and be much harder to find. In that scenario, there could be up to one antistar lurking among every 10 normal stars.
But proving that any celestial object is an antistar would be extremely difficult, because besides the gamma rays that could arise from matter-antimatter annihilation, the light given off by antistars is expected to look just like the light from normal stars. “It would be practically impossible to say that [the candidates] are actually antistars,” says study coauthor Simon Dupourqué, an astrophysicist at the Institute of Research in Astrophysics and Planetology in Toulouse, France. “It would be much easier to disprove.”
Astronomers could watch how gamma rays or radio signals from the candidates change over time to double-check that these objects aren’t really pulsars. Researchers could also look for optical or infrared signals that might indicate the candidates are actually black holes.
“Obviously this is still preliminary … but it’s interesting,” says Julian Heeck, a physicist at the University of Virginia in Charlottesville not involved in the work.
The existence of antistars would imply that substantial amounts of antimatter somehow managed to survive in isolated pockets of space. But Heeck doubts that antistars, if they exist, would be abundant enough to account for all the universe’s missing antimatter. “You would still need an explanation for why matter overall dominates over antimatter.” More
This is the first picture of an exoplanet from the James Webb Space Telescope.
“We’re actually measuring photons from the atmosphere of the planet itself,” says astronomer Sasha Hinkley of the University of Exeter in England. Seeing those particles of light, “to me, that’s very exciting.”
The planet is about seven times the mass of Jupiter and lies more than 100 times farther from its star than Earth sits from the sun, direct observations of exoplanet HIP 65426 b show. It’s also young, about 10 million or 20 million years old, compared with the more than 4-billion-year-old Earth, Hinkley and colleagues report in a study submitted August 31 at arXiv.org.
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Those three features — size, distance and youth — made HIP 65426 b relatively easy to see, and so a good planet to test JWST’s observing abilities. And the telescope has once again surpassed astronomers’ expectations (SN: 7/11/22).
“We’ve demonstrated really how powerful JWST is as an instrument for the direct imaging of exoplanets,” says exoplanet astronomer and coauthor Aarynn Carter of the University of California, Santa Cruz.
Astronomers have found more than 5,000 planets orbiting other stars (SN: 3/22/22). But almost all of those planets were detected indirectly, either by the planets tugging on the stars with their gravity or blocking starlight as they cross between the star and a telescope’s view.
To see a planet directly, astronomers have to block out the light from its star and let the planet’s own light shine, a tricky process. It’s been done before, but for only about 20 planets total (SN: 11/13/08; SN: 3/14/13; SN: 7/22/20).
“In every area of exoplanet discovery, nature has been very generous,” says MIT astrophysicist Sara Seager, who was not involved in the JWST discovery. “This is the one area where nature didn’t really come through.”
In 2017, astronomers discovered HIP 65426 b and took a direct image of it using an instrument on the Very Large Telescope in Chile. But because that telescope is on the ground, it can’t see all the light coming from the exoplanet. Earth’s atmosphere absorbs a lot of the planet’s infrared wavelengths — exactly the wavelengths JWST excels at observing. The space telescope observed the planet on July 17 and July 30, capturing its glow in four different infrared wavelengths.
“These are wavelengths of light that we’ve never ever seen exoplanets in before,” Hinkley says. “I’ve literally been waiting for this day for six years. It feels amazing.”
Pictures in these wavelengths will help reveal how planets formed and what their atmospheres are made of.
“Direct imaging is our future,” Seager says. “It’s amazing to see the Webb performing so well.”
While the team has not yet studied the atmosphere of HIP 65426 b in detail, it did report the first spectrum — a measurement of light in a range of wavelengths — of an object orbiting a different star. The spectrum allows a deeper look into the object’s chemistry and atmosphere, astronomer Brittany Miles of UC Santa Cruz and colleagues reported September 1 at arXiv.org.
That object is called VHS 1256 b. It’s as heavy as 20 Jupiters, so it may be more like a transition object between a planet and a star, called a brown dwarf, than a giant planet. JWST found evidence that the amounts of carbon monoxide and methane in the atmosphere of the orb are out of equilibrium. That means the atmosphere is getting mixed up, with winds or currents pulling molecules from lower depths to its top and vice versa. The telescope also saw signs of sand clouds, a common feature in brown dwarf atmospheres (SN: 7/8/22).
“This is probably a violent and turbulent atmosphere that is filled with clouds,” Hinkley says.
HIP 65426 b and VHS 1256 b are unlike anything we see in our solar system. They’re more than three times the distance of Uranus from their stars, which suggests they formed in a totally different way from more familiar planets. In future work, astronomers hope to use JWST to image smaller planets that sit closer to their stars.
“What we’d like to do is get down to study Earths, wouldn’t we? We’d really like to get that first image of an Earth orbiting another star,” Hinkley says. That’s probably out of JWST’s reach — Earth-sized planets are still too small see. But a Saturn? That may be something JWST could focus its sights on. More
Late in the evening of February 28, 2021, a coal-dark space rock about the size of a soccer ball fell through the sky over northern England. The rock blazed in a dazzling, eight-second-long streak of light, split into fragments and sped toward the Earth. The largest piece went splat in the driveway of Rob and Cathryn Wilcock in the small, historic town of Winchcombe.
An analysis of those fragments now shows that the meteorite came from the outer solar system, and contains water that is chemically similar to Earth’s, scientists report November 16 in Science Advances. How Earth got its water remains one of science’s enduring mysteries. The new results support the idea that asteroids brought water to the young planet (SN: 5/6/15).
The Wilcocks were not the only ones who found pieces of the rock that fell that night. But they were the first. Bits of the Winchcombe meteorite were collected within 12 hours after they hit the ground, meaning they are relatively uncontaminated with earthly stuff, says planetary scientist Ashley King of London’s Natural History Museum.
The first bits of the Winchcombe meteorite to be recovered were from Rob and Cathryn Wilcock’s driveway in England. The meteorite was so brittle it shattered on impact and made only a small dent in the driveway.R. Wilcock
Other meteorites have been recovered after being tracked from space to the ground, but never so quickly (SN: 12/20/12).
“It’s as pristine as we’re going to get from a meteorite,” King says. “Other than it landing in the museum on my desk, or other than sending a spacecraft up there, we can’t really get them any quicker or more pristine.”
After collecting about 530 grams of meteorite from Winchcombe and other sites, including a sheep field in Scotland, King and colleagues threw a kitchen sink of lab techniques at the samples. The researchers polished the material, heated it and bombarded it with electrons, X-rays and lasers to figure out what elements and minerals it contained.
The team also analyzed video of the fireball from the UK Fireball Alliance, a collaboration of 16 meteor-watching cameras around the world, plus many more videos from doorbell and dashboard cameras. The films helped to determine the meteorite’s trajectory and where it originated.
The meteorite is a type of rare, carbon-rich rock called a carbonaceous chondrite, the team found. It came from an asteroid near the orbit of Jupiter, and got its start toward Earth around 300,000 years ago, a relatively short time for a trip through space, the researchers calculate.
Chemical analyses also revealed that the meteorite is about 11 percent water by weight, with the water locked in hydrated minerals. Some of the hydrogen in that water is actually deuterium, a heavy form of hydrogen, and the ratio of hydrogen to deuterium in the meteorite is similar to that of the Earth’s atmosphere. “It’s a good indication that water [on Earth] was coming from water-rich asteroids,” King says.
Researchers also found amino acids and other organic material in the meteorite pieces. “These are the building blocks for things like DNA,” King says. The pieces “don’t contain life, but they have the starting point for life locked up in them.” Further studies can help determine how those molecules formed in the asteroid that the meteorite came from, and how similar organic material could have been delivered to the early Earth.
“It’s always exciting to have access to material that can provide a new window into an early time and place in our solar system,” says planetary scientist Meenakshi Wadhwa of Arizona State University in Tempe, who was not involved in the study.
She hopes future studies will compare the samples of the Winchcombe meteorite to samples of asteroids Ryugu and Bennu, which were collected by spacecraft and sent back to Earth (SN: 1/15/19). Those asteroids are both closer to Earth than the main asteroid belt, where the Winchcombe meteorite came from. Comparing and contrasting all three samples will build a more complete picture of the early solar system’s makeup, and how it evolved into what we see today. More
