Liquid brine can hang around on Mars’ surface, a new study suggests, but conditions may not be great for life as we know it. That’s bad news for any Earth-based microorganisms determined to colonize the Red Planet, but good news for humans who don’t want to contaminate Mars with microbes hitching a ride on robot […] More

A fast-spinning neutron star south of the constellation Leo is the most massive of its kind seen so far, according to new observations.

The record-setting collapsed star, named PSR J0952-0607, weighs about 2.35 times as much as the sun, researchers report July 11 on arXiv.org. “That’s the heaviest well-measured neutron star that has been found to date,” says study coauthor Roger Romani, an astrophysicist at Stanford University.

The previous record holder was a neutron star in the northern constellation Camelopardalis named PSR J0740+6620, which tipped the scales at about 2.08 times as massive as the sun. If a neutron star grows too massive, it collapses under its own weight and becomes a black hole. These measurements of hefty neutron stars are of interest because no one knows the exact mass boundary between neutron stars and black holes.

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That dividing line drives the quest to find the most massive neutron stars and determine just how massive they can be, Romani says. “It’s defining the boundary between the visible things in the universe and the stuff that is forever hidden from us inside of a black hole,” he says. “A neutron star that’s on the hairy edge of becoming a black hole — just about heavy enough to collapse — has at its center the very densest material that we can access in the entire visible universe.”

PSR J0952-0607 is in the constellation Sextans, just south of Leo. It resides 20,000 light-years from Earth, far above the galaxy’s plane in the Milky Way’s halo. The neutron star emits a pulse of radio waves toward us each time it spins, so astronomers also classify the object as a pulsar. First reported in 2017, this pulsar spins every 1.41 milliseconds, faster than all but one other pulsar.

That’s why Romani and his colleagues chose to study it — the fast spin led them to suspect that the pulsar might be unusually heavy. That’s because another star orbits the pulsar, and just as water spilling over a water wheel spins it up, gas falling from that companion onto the pulsar could have sped up its rotation while also boosting its mass.

Observing the companion, Romani and his colleagues found that it whips around the pulsar quickly — at about 380 kilometers per second. Using the companion’s speed and its orbital period of about six and a half hours, the team calculated the pulsar’s mass to be more than twice the mass of the sun. That’s a lot heavier than the typical neutron star, which is only about 1.4 times as massive as the sun.

“It’s a terrific study,” says Emmanuel Fonseca, a radio astronomer at West Virginia University in Morgantown who measured the mass of the previous record holder but was not involved in the new work. “It helps nuclear physicists actually constrain the nature of matter within these extreme environments.” More

Bright, artificial lights are drowning out the night sky’s natural glow. Now, an exhibition is highlighting some of the consequences of a fading starry night — and how people can help restore it.

“Lights Out,” open through 2025 at the Smithsonian National Museum of Natural History in Washington, D.C., illuminates how light pollution is affecting astronomy, natural ecosystems and human cultures around the world. “We want people to understand that it’s a global problem, and it’s having broad impact,” says Jill Johnson, an exhibit developer at the museum.

Upon entering the exhibition, the dimly lit space resets the mood for nighttime exploration. The exhibition spans a long hallway that can be entered from either end. One entrance quickly draws in visitors with a personal connection. An interactive display invites you to experience your own night sky, whether in a city, suburb or remote location. Three tactile panels feature raised elements, including dots representing light pollution and crosses indicating visible stars. The more populated a place, the more dots are smattered across the panel.

Visitors can also listen to the artificial light and starlight in each sky through data that have been translated into sound. The multisensory experience is especially engaging for visitors who may not be able to experience the exhibition visually.

The other entrance offers a more didactic introduction to the exhibition. A timeline presents a brief history of human-made light, from fire-lit torches to today’s LEDs, and then segues to astronomy (SN: 1/19/23). Space scientists rely on light, both visible and not, to understand celestial bodies. And their views of the universe have become increasingly obstructed by artificial light.

“Astronomers were some of the first folks to sound the alarm on light pollution,” says Ryan Lavery, a public affairs specialist at the museum.

Astronomers aren’t the only scientists who have noticed the repercussions. Biologists have observed light pollution’s toll on plants and animals, whether harming corals’ moonlight-triggered reproduction or bats’ ability to pollinate flowers. Here, much of the evidence on display is visual. Photographs and specimens demonstrate the variety of critters that are active at night, while a glass case of preserved birds presents the grim consequences of light pollution. All of these birds died from striking buildings in Washington, D.C., or Baltimore after being disoriented by the bright cityscapes.

Losing dark, starry nights also affects human cultures. Another area of the exhibition presents people’s ancient and modern-day connections to the night sky through photographs, stories and cultural items. A glistening beadwork depicting the Milky Way was crafted specially for “Lights Out” by Gwich’in artist Margaret Nazon, who grew up staring at the stars in Canada’s Northwest Territories.

Our connections under a shared sky are emphasized in the exhibition’s small central theater. It replicates a starry night over Coudersport, Pa., through speckled lighting and walls bearing illustrations of trees and hills. A short film describes the star cluster Messier 45, also known as the Pleiades, and explains the stars’ origins according to tales from three cultures — the ancient Greeks, the Ainu in Japan and the Māori in New Zealand.

“Cultures all over the world have a deep relationship to the night sky,” says Stephen Loring, cocurator of the exhibition and an archaeologist at the museum. “If we lose the night sky, we lose an avenue to our understanding of what it is to be a human being.”

But the exhibition isn’t all bleak. Sprinkled throughout it are success stories of how people are reducing light pollution, from France’s outdoor lighting curfews to beach communities that have altered their lighting systems to avoid drawing hatchling sea turtles away from the ocean. And visitors may be heartened to learn about simple but meaningful actions that they can take, such as aiming outdoor lights downward and using the dimmest settings.

Overall, “Lights Out” instills a sense of hope and a desire to reconnect with the night sky. “This is an optimistic exhibition,” Loring says. “We can solve this problem.” More

Earth is awash in gravitational waves.
Over a six-month period, scientists captured a bounty of 39 sets of gravitational waves. The waves, which stretch and squeeze the fabric of spacetime, were caused by violent events such as the melding of two black holes into one.
The haul was reported by scientists with the LIGO and Virgo experiments in several studies posted October 28 on a collaboration website and at arXiv.org. The addition brings the tally of known gravitational wave events to 50.
The bevy of data, which includes sightings from April to October 2019, suggests that scientists’ gravitational wave–spotting skills have leveled up. Before this round of searching, only 11 events had been detected in the years since the effort began in 2015. Improvements to the detectors — two that make up the Advanced Laser Interferometer Gravitational-Wave Observatory, or LIGO, in the United States, and another, Virgo, in Italy — have dramatically boosted the rate of gravitational wave sightings.

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While colliding black holes produced most of the ripples, a few collisions seem to have involved neutron stars, ultradense nuggets of matter left behind when stars explode.
Some of the events added to the gravitational wave register had been previously reported individually, including the biggest black hole collision spotted so far (SN: 9/2/20) and a collision between a black hole and an object that couldn’t be identified as either a neutron star or black hole (SN: 6/23/20).
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Gravitational waves are produced when two massive objects, such as black holes, spiral around one another and merge. These visualizations, which are based on computer simulations, show these merging objects for 38 of the 50 known gravitational wave events.
What’s more, some of the coalescing black holes seem to be very large and spinning rapidly, says astrophysicist Richard O’Shaughnessy of the Rochester Institute of Technology in New York, a member of the LIGO collaboration. That’s something “really compelling in the data now that we hadn’t seen before,” he says. Such information might help reveal the processes by which black holes get partnered up before they collide (SN: 6/19/16).
Scientists also used the smorgasbord of smashups to further check Albert Einstein’s theory of gravity, general relativity, which predicts the existence of gravitational waves. When tested with the new data — surprise, surprise — Einstein came up a winner. More

A distant galaxy has been caught in the act of shutting down.
The galaxy, called CQ 4479, is still forming plenty of new stars. But it also has an actively feeding supermassive black hole at its center that will bring star formation to a halt within a few hundred million years, astronomers reported January 11 at the virtual meeting of the American Astronomical Society. Studying this galaxy and others like it will help astronomers figure out exactly how such shutdowns happen.
“How galaxies precisely die is an open question,” says astrophysicist Allison Kirkpatrick of the University of Kansas in Lawrence. “This could give us a lot of insight into that process.”
Astronomers think galaxies typically start out making new stars with a passion. The stars form from pockets of cold gas that contract under their own gravity and ignite thermonuclear fusion in their centers. But at some point, something disrupts the cold star-forming fuel and sends it toward the supermassive black hole at the galaxy’s core. That black hole gobbles the gas, heating it white-hot. An actively feeding black hole can be seen from billions of light-years away and is known as a quasar. Radiation from the hot gas pumps extra energy into the rest of the galaxy, blowing away or heating up the remaining gas until the star-forming factory closes for good (SN: 3/5/14).

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That picture fits with the types of galaxies astronomers typically see in the universe: “blue and new” star formers, and “red and dead” dormant galaxies. But while examining data from large surveys of the sky, Kirkpatrick and colleagues noticed another type. The team found about two dozen galaxies that emit energetic X-rays characteristic of an actively gobbling black hole, but also shine in low-energy infrared light, revealing that there is still cold gas somewhere in the galaxies. Kirkpatrick and colleagues dubbed these galaxies “cold quasars” in a paper in the Sept. 1 Astrophysical Journal.
“When you see a black hole actively accreting material, you expect that star formation has already shut down,” says coauthor and astrophysicist Kevin Cooke, also of the University of Kansas, who presented the research at the meeting. “But cold quasars are in a weird time when the black hole in the center has just begun to feed.”
To investigate individual cold quasars in more detail, Kirkpatrick and Cooke used SOFIA, an airplane outfitted with a telescope that can see in a range of infrared wavelengths that the original cold quasar observations didn’t cover. SOFIA looked at CQ 4479, a cold quasar about 5.25 billion light-years away, in September 2019.
The observations showed that CQ 4479 has about 20 billion times the mass of the sun in stars, and it’s adding about 95 suns per year. (That’s a furious rate compared with the Milky Way; our home galaxy builds two or three solar masses of new stars per year.) CQ 4479’s central black hole is 24 million times as massive as the sun, and it’s growing at about 0.3 solar masses per year. In terms of percentage of their total mass, the stars and the black hole are growing at the same rate, Kirkpatrick says.
The cold quasar CQ 4479, the blue fuzzy dot at the center of this image, showed up in images taken by the Sloan Digital Sky Survey. The red dot nearby might be another galaxy interacting with CQ 4479, or it could be unrelated.K.C. Cooke et al/arxiv.org 2020, Sloan Digital Sky Survey
That sort of “lockstep evolution” runs counter to theories of how galaxies wax and wane. “You should have all your stars finish growing first, and then your black hole grows,” Kirkpatrick says. “This [galaxy] shows there’s a period that they actually do grow together.”
Cooke and colleagues estimated that in half a billion years, the galaxy will host 100 billion solar masses of stars, but its black hole will be passive and quiet. All the cold star-forming gas will have heated up or blown away.
The observations of CQ 4479 support the broad ideas of how galaxies die, says astronomer Alexandra Pope of the University of Massachusetts Amherst, who was not involved in the new work. Given that galaxies eventually switch off their star formation, it makes sense that there should be a period of transition. The findings are a “confirmation of this important phase in the evolution of galaxies,” she says. Taking a closer look at more cold quasars will help astronomers figure out just how quickly galaxies die. More