Space & Astronomy

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

The dwarf planet Quaoar has a ring that is too big for its metaphorical fingers. While all other rings in the solar system lie within or near a mathematically determined distance of their parent bodies, Quaoar’s ring is much farther out.

“For Quaoar, for the ring to be outside this limit is very, very strange,” says astronomer Bruno Morgado of the Federal University of Rio de Janeiro. The finding may force a rethink of the rules governing planetary rings, Morgado and colleagues say in a study published February 8 in Nature.

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Quaoar is an icy body about half the size of Pluto that’s located in the Kuiper Belt at the solar system’s edge (SN: 8/23/22). At such a great distance from Earth, it’s hard to get a clear picture of the world.

So Morgado and colleagues watched Quaoar block the light from a distant star, a phenomenon called a stellar occultation. The timing of the star winking in and out of view can reveal details about Quaoar, like its size and whether it has an atmosphere.

The researchers took data from occultations from 2018 to 2020, observed from all over the world, including Namibia, Australia and Grenada, as well as space. There was no sign that Quaoar had an atmosphere. But surprisingly, there was a ring. The finding makes Quaoar just the third dwarf planet or asteroid in the solar system known to have a ring, after the asteroid Chariklo and the dwarf planet Haumea (SN: 3/26/14; SN: 10/11/17).

Even more surprisingly, “the ring is not where we expect,” Morgado says.

Known rings around other objects lie within or near what’s called the Roche limit, an invisible line where the gravitational force of the main body peters out. Inside the limit, that force can rip a moon to shreds, turning it into a ring. Outside, the gravity between smaller particles is stronger than that from the main body, and rings will coalesce into one or several moons.

“We always think of [the Roche limit] as straightforward,” Morgado says. “One side is a moon forming, the other side is a ring stable. And now this limit is not a limit.”

For Quaoar’s far-out ring, there are a few possible explanations, Morgado says. Maybe the observers caught the ring at just the right moment, right before it turns into a moon. But that lucky timing seems unlikely, he notes.

Maybe Quaoar’s known moon, Weywot, or some other unseen moon contributes gravity that holds the ring stable somehow. Or maybe the ring’s particles are colliding in such a way that they avoid sticking together and clumping into moons.

The particles would have to be particularly bouncy for that to work, “like a ring of those bouncy balls from toy stores,” says planetary scientist David Jewitt of UCLA, who was not involved in the new work.

The observation is solid, says Jewitt, who helped discover the first objects in the Kuiper Belt in the 1990s. But there’s no way to know yet which of the explanations is correct, if any, in part because there are no theoretical predictions for such far-out rings to compare with Quaoar’s situation.

That’s par for the course when it comes to the Kuiper Belt. “Everything in the Kuiper Belt, basically, has been discovered, not predicted,” Jewitt says. “It’s the opposite of the classical model of science where people predict things and then confirm or reject them. People discover stuff by surprise, and everyone scrambles to explain it.”

More observations of Quaoar, or more discoveries of seemingly misplaced rings elsewhere in the solar system, could help reveal what’s going on.

“I have no doubt that in the near future a lot of people will start working with Quaoar to try to get this answer,” Morgado says. More

SEATTLE — Luke Skywalker’s home planet in Star Wars is the stuff of science fiction. But Tatooine-like planets in orbit around pairs of stars might be our best bet in the search for habitable planets beyond our solar system.

Many stars in the universe come in pairs. And lots of those should have planets orbiting them (SN: 10/25/21). That means there could be many more planets orbiting around binaries than around solitary stars like ours. But until now, no one had a clear idea about whether those planets’ environments could be conducive to life. New computer simulations suggest that, in many cases, life could imitate art.

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Earthlike planets orbiting some configurations of binary stars can stay in stable orbits for at least a billion years, researchers reported January 11 at the American Astronomical Society meeting. That sort of stability, the researchers propose, would be enough to potentially allow life to develop, provided the planets aren’t too hot or cold.

Of the planets that stuck around, about 15 percent stayed in their habitable zone — a temperate region around their stars where water could stay liquid — most or even all of the time.

The researchers ran simulations of 4,000 configurations of binary stars, each with an Earthlike planet in orbit around them. The team varied things like the relative masses of the stars, the sizes and shapes of the stars’ orbits around each other, and the size of the planet’s orbit around the binary pair.

The scientists then tracked the motion of the planets for up to a billion years of simulated time to see if the planets would stay in orbit over the sorts of timescales that might allow life to emerge.

A planet orbiting binary stars can get kicked out of the star system due to complicated interactions between the planet and stars. In the new study, the researchers found that, for planets with large orbits around star pairs, only about 1 out of 8 were kicked out of the system. The rest were stable enough to continue to orbit for the full billion years. About 1 in 10 settled in their habitable zones and stayed there.

Of the 4,000 planets that the team simulated, roughly 500 maintained stable orbits that kept them in their habitable zones at least 80 percent of the time.

“The habitable zone . . . as I’ve characterized it so far, spans from freezing to boiling,” said Michael Pedowitz, an undergraduate student at the College of New Jersey in Ewing who presented the research. Their definition is overly strict, he said, because they chose to model Earthlike planets without atmospheres or oceans. That’s simpler to simulate, but it also allows temperatures to fluctuate wildly on a planet as it orbits.

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“An atmosphere and oceans would smooth over temperature variations fairly well,” says study coauthor Mariah MacDonald, an astrobiologist also at the College of New Jersey. An abundance of air and water would potentially allow a planet to maintain habitable conditions, even if it spent more of its time outside of the nominal habitable zone around a binary star system.

The number of potentially habitable planets “will increase once we add atmospheres,” MacDonald says, “but I can’t yet say by how much.”

She and Pedowitz hope to build more sophisticated models in the coming months, as well as extend their simulations beyond a billion years and include changes in the stars that can affect conditions in a solar system as it ages.

The possibility of stable and habitable planets in binary star systems is a timely issue says Penn State astrophysicist Jason Wright, who was not involved in the study.

“At the time Star Wars came out,” he says, “we didn’t know of any planets outside the solar system, and wouldn’t for 15 years. Now we know that there are many and that they orbit these binary stars.”

These simulations of planets orbiting binaries could serve as a guide for future experiments, Wright says. “This is an under-explored population of planets. There’s no reason we can’t go after them, and studies like this are presumably showing us that it’s worthwhile to try.” More

The night sky has been brightening faster than researchers realized, thanks to the use of artificial lights at night. A study of more than 50,000 observations of stars by citizen scientists reveals that the night sky grew about 10 percent brighter, on average, every year from 2011 to 2022.

In other words, a baby born in a region where roughly 250 stars were visible every night would see only 100 stars on their 18th birthday, researchers report in the Jan. 20 Science.

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The perils of light pollution go far beyond not being able to see as many stars. Too much brightness at night can harm people’s health, send migrating birds flying into buildings, disrupt food webs by drawing pollinating insects toward lights instead of plants and may even interrupt fireflies trying to have sex (SN: 8/2/17; SN: 8/12/15).

“In a way, this is a call to action,” says astronomer Connie Walker of the National Optical-Infrared Astronomy Research Laboratory in Tucson. “People should consider that this does have an impact on our lives. It’s not just astronomy. It impacts our health. It impacts other animals who cannot speak for themselves.”

Walker works with the Globe at Night campaign, which began in the mid-2000s as an outreach project to connect students in Arizona and Chile and now has thousands of participants worldwide. Contributors compare the stars they can see with maps of what stars would be visible at different levels of light pollution, and enter the results on an app.

“I’d been quite skeptical of Globe at Night” as a tool for precision research, admits physicist Christopher Kyba of the GFZ German Research Centre for Geosciences in Potsdam. But the power is in the sheer numbers: Kyba and colleagues analyzed 51,351 individual data points collected from 2011 to 2022.

“The individual data are not precise, but there’s a whole lot of them,” he says. “This Globe at Night project is not just a game; it’s really useful data. And the more people participate, the more powerful it gets.”

Those data, combined with a global atlas of sky luminance published in 2016, allowed the team to conclude that the night sky’s brightness increased by an average 9.6 percent per year from 2011 to 2022 (SN: 6/10/16).

Most of that increase was missed by satellites that collect brightness data across the globe. Those measurements saw just a 2 percent increase in brightness per year over the last decade.

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There are several reasons for that, Kyba says. Since the early 2010s, many outdoor lights have switched from high-pressure sodium lightbulbs to LEDs. LEDs are more energy efficient, which has environmental benefits and cost savings.

But LEDs also emit more short-wavelength blue light, which scatters off particles in the atmosphere more than sodium bulbs’ orange light, creating more sky glow. Existing satellites are not sensitive to blue wavelengths, so they underestimate the light pollution coming from LEDs. And satellites may miss light that shines toward the horizon, such as light emitted by a sign or from a window, rather than straight up or down.

Satellites have missed some of the light pollution from LEDs, which emit in blue wavelengths. This image from the International Space Station shows LEDs in the center of Milan glowing brighter than the orange lights in the suburbs.Samantha Cristoforetti, NASA, ESA

Astronomer and light pollution researcher John Barentine was not surprised that satellites underestimated the problem. But “I was still surprised by how much of an underestimate it was,” he says. “This paper is confirming that we’ve been undercounting light pollution in the world.”

The good news is that no major technological breakthroughs are needed to help fix the problem. Scientists and policy makers just need to convince people to change how they use light at night — easier said than done.

“People sometimes say light pollution is the easiest pollution to solve, because you just have to turn a switch and it goes away,” Kyba says. “That’s true. But it’s ignoring the social problem — that this overall problem of light pollution is made by billions of individual decisions.”

Some simple solutions include dimming or turning off lights overnight, especially floodlighting or lights in empty parking lots.

Kyba shared a story about a church in Slovenia that switched from four 400-watt floodlights to a single 58-watt LED, shining behind a cutout of the church to focus the light on its facade. The result was a 96 percent reduction in energy use and much less wasted light , Kyba reported in the International Journal of Sustainable Lighting in 2018. The church was still lit up, but the grass, trees and sky around it remained dark.

“If it was possible to replicate that story over and over again throughout our society, it would suggest you could really drastically reduce the light in the sky, still have a lit environment and have better vision and consume a lot less energy,” he says. “This is kind of the dream.”

Barentine, who leads a private dark-sky consulting firm, thinks widespread awareness of the problem — and subsequent action — could be imminent. For comparison, he points to a highly publicized oil slick fire on the Cuyahoga River, outside of Cleveland, in 1969 that fueled the environmental movement of the 1960s and ’70s, and prompted the U.S. Congress to pass the Clean Water Act.

“I think we’re on the precipice, maybe, of having the river-on-fire moment for light pollution,” he says. More

Galaxies that helped transform the early universe may have been small, round and green.

Astronomers using the James Webb Space Telescope have spotted “Green Pea” galaxies dating to 13.1 billion years ago. These viridescent runts, spotted just 700 million years after the Big Bang, might have helped trigger one of the greatest makeovers in cosmic history, astronomers said at a January 9 news conference in Seattle at the American Astronomical Society’s annual meeting.

Green Peas first showed up in 2009 in images from the Sloan Digital Sky Survey, an ambitious project to map much of the sky. Citizen science volunteers gave the objects their colorful name. Their greenish hue is because most of their light comes from glowing gas clouds, rather than directly from stars.

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These galaxies are rare in the present-day universe. Astronomers think that the ones that do exist are analogs of galaxies that were more plentiful in the early universe.

“They’re a bit like living fossils,” said astrophysicist James Rhoads of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Coelacanths, if you will,” referencing a fish thought to be extinct until it showed up off the coast of South Africa in 1938 (SN: 12/2/11). 

These galaxies leak much more ultraviolet light, which can rip electrons from atoms, than typical galaxies do. So Green Peas dating to the universe’s first billion years or so could be partly responsible for a dramatic and mysterious cosmic transition called reionization, when most of the hydrogen atoms in the early universe had their electrons torn away (SN: 1/7/20).

Three ancient Green Peas turned up in JWST’s first image, released in July 2022 (SN: 7/21/22). The objects look red in JWST’s infrared vision, but the wavelengths of light they emit are like those of the previously discovered Green Peas. The findings were also published in the Jan. 1 Astrophysical Journal Letters.

“This helps us explain how the universe reionized,” Rhoads said. “I think this is an important piece of the puzzle.” More