SCIENCE

JWST captures stunning image of a star about to go supernova

Published

3 days ago

March 15, 2023

Jan Topete

A bright, hot star known as Wolf-Rayet 124 (WR 124).

IMAGE: NASA, ESA, CSA, STScI, Webb ERO production team.

At a distance of about 15,000 light years, the star is preparing to go supernova. The James Webb Space Telescope (JWST) has captured a beautiful image of a massive star known as a Wolf-Rayet star that has begun shedding its outer layers before going supernova.

This star is called WR 124 and is about 30 times more massive than the Sun. When the core of such huge stars runs out of hydrogen, they instead begin to synthesize heavier elements. This merger creates powerful bursts of energy, throwing out gusts of wind at millions of kilometers per hour.

Powerful winds rip off the star’s outer layers, resulting in a huge cloud of dust and gas similar to the one seen in this JWST image. The researchers calculated that WR 124 has already lost about 10 times the mass of the Sun.

As soon as the star runs out of heavy elements, it will explode. The Wolf-Rayet phase of a massive star’s life is relatively short, a few million years at most, before the star explodes.

However, the dust that the star is producing at this time may be of cosmic significance. The details of the JWST observations should help astronomers figure out exactly how this dust behaves and whether the dust grains are large and numerous enough to survive an impending supernova.

This is important not only because of the role that dust plays in the evolution of the universe, shaping the environment in which cosmic building blocks grow, but also because researchers believe there is much more dust in the universe than our best theories of dust formation can explain. . Determining how dust behaves around Wolf-Rayet stars like WR 124 can help us understand where all that extra dust is coming from.

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SCIENCE

New evidence links pandemic origin to raccoon dogs at a market in Wuhan

Published

7 hours ago

March 17, 2023

Jan Topete

An international panel of virus experts said on Thursday they had found genetic data at a market in Wuhan, China that linked the coronavirus to raccoon dogs for sale there, adding evidence that the worst pandemic in a century could have been caused by the virus. an infected animal that has been sold through the illegal wildlife trade.

The genetic data was taken from swabs taken in and around the Huanan Seafood Wholesale Market starting in January 2020, shortly after Chinese authorities closed the market over suspicions that it was linked to a novel virus outbreak. By that time, the animals had already been removed, but the researchers were smearing walls, floors, metal cages and carts that were often used to transport animal cages.

In samples that tested positive for the coronavirus, an international research team found animal genetic material, including a large amount that matched a raccoon dog, three scientists involved in the analysis said.

Mixing the genetic material of the virus and the animal does not prove that the raccoon dog itself was infected. And even if a raccoon dog were infected, it would not be clear that the animal transmitted the virus to humans. Another animal could have transmitted the virus to humans, or someone infected with the virus could have passed the virus to a raccoon dog.

But the analysis did establish that raccoon dogs — furry animals that are related to foxes and known to be able to transmit the coronavirus — deposited genetic signatures in the same place where the genetic material from the virus was left, the three scientists said. This evidence, they say, is consistent with a scenario in which the virus entered humans from a wild animal.

A full report on the findings of the international research team has not yet been published. Their analysis was first reported Atlantic Ocean.

The new data is sure to revive the debate about the origin of the pandemic, even if it does not address the question of how it began.

In recent weeks, the so-called lab leak theory, which claims the coronavirus originated from a research lab in Wuhan, has gained traction thanks to a new intelligence assessment by the U.S. Department of Energy and hearings led by new Republican Chamber leadership.

But genetic data from the market offers some of the most tangible evidence of how the virus could have entered humans from wild animals outside the lab. It also suggests that Chinese scientists have given an incomplete account of the evidence that could fill in the details about how the virus spread in the Huanan market. .

Jeremy Kamil, a virologist at the Louisiana State University Health Sciences Center at Shreveport, who was not involved in the study, said the results showed “samples from the market that had early Covid lines were contaminated with wild animal DNA reads.”

Dr Kamil said he lacked conclusive evidence that an infected animal caused the pandemic. But, he says, “it really brings out the illegal animal trade in a personal way.”

Chinese scientists released study considering the same market samples in February 2022. This study reported that the samples were positive for coronavirus, but it was assumed that the virus came from infected people who shopped or worked at the market, and not from the animals that were sold there.

At some point, the same researchers, including those affiliated with the Chinese Centers for Disease Control and Prevention, posted raw swab data from the market to GISAID, the international repository for viral genetic sequences. (Attempts to contact Chinese scientists by phone on Thursday were unsuccessful.)

On March 4, Florence Debarre, an evolutionary biologist at the French National Center for Scientific Research, accidentally searched the database for information related to the Huanan market when, she said in an interview, she noticed that more sequences than usual were showing up. first about whether they contained new data, dr. DeBarr put them aside, only to log back in last week to find they had a lot of raw data stored in them.

Virus experts have been waiting for this raw sequence data from the market since they learned of its existence in a February 2022 Chinese report. Debarre said she alerted other scientists, including the leaders of a group that published a number of studies last year pointing to the market as the source.

An international team that included Michael Sparrow, an evolutionary biologist at the University of Arizona; Christian Andersen, virologist at the Scripps Research Institute in California; and Edward Holmes, a biologist at the University of Sydney, began collecting new genetic data last week.

One specimen in particular caught their attention. It was taken from a cart tied to a specific stall in the Huanan Market where Dr. S. Holmes visited in 2014, according to scientists involved in the analysis. This tent, doctor. Holmes found that raccoon dogs were kept in a cage on top of a separate cage with birds, and this is precisely the environment that facilitates the transmission of new viruses.

The research team found that a swab taken from a cart in early 2020 contained virus and raccoon dog genetic material.

“We were able to figure out relatively quickly that at least one of those samples had a lot of raccoon dog nucleic acid, along with virus nucleic acid,” said Steven Goldstein, a virologist at the University of Utah who worked on the study. new analysis. (Nucleic acids are the chemical building blocks that carry genetic information.)

After the international team stumbled upon the new data, they approached the Chinese researchers who uploaded the files to collaborate while respecting the rules of the online repository, the scientists involved in the new analysis said. After that, the sequences disappeared from GISAID.

It is not clear who removed them or why they were removed.

Dr. Debarre said the research team was looking for more data, including some of the market samples that have never been released to the public. “The important thing is that there is even more data,” she said.

Scientists involved in the analysis said some of the samples also contained genetic material from other animals and humans. Angela Rasmussen, a virologist with the Organization for Vaccines and Infectious Diseases at the University of Saskatchewan in Canada who worked on the analysis, said the human genetic material was to be expected given that people shopped and worked there and cases of Covid in humans were reported. were connected to the market.

Dr. Goldstein also warned that “we don’t have an infected animal, and we can’t prove for sure that there was an infected animal in that stall.” The genetic material of the virus is quite stable, he said, so it is not clear exactly when it entered the market. He said the team was still analyzing the data and that it had no intention of releasing its analysis prior to releasing the report.

“But,” he said, “given that the animals that were on the market were not selected at the time, this is the best we can hope for.”

SCIENCE

Rare, dusty dying star shown in new JWST image

Published

8 hours ago

March 17, 2023

Jan Topete

Giant stars can be a prime example of the “live fast, die young” principle. Unlike our own Sun, which will shine for billions of years, more massive stars can burn off their fusion fuel in just a few million years before shedding their outer layers and exploding in supernovae.

NASA this week presented a rare image from the James Webb Space Telescope (JWST) of one of these stellar giants, Wolf-Rayet stars in the last, fleeting stages of their lives. Named WR 124, it lies in the constellation Sagittarius and lies about 15,000 light-years from Earth. The dying star has at least 30 times the mass of our Sun, but it is rapidly contracting, expelling hot gas into the cold vacuum of space.

“We caught it before,” explains Anthony Moffat, a retired astrophysicist who previously observed WR 124 with the Hubble Space Telescope and was not involved in the recent JWST measurements. Moffat has been studying Wolf-Rayet stars for decades. “This is the youngest person I know,” he says. The colorful cloud in the image, somewhat erroneously called a planetary nebula, is only a few thousand years old. Now, “the nebula is hugging the star,” he says. But as time passes, it will bloom outward in the form of expanding shells or rings of gas and dust.

Stars are natural fusion reactors, glowing with the energy released when hydrogen is fused to form helium atoms. Once massive stars burn off all their hydrogen, they begin to convert helium into heavier elements through a more energetic fusion reaction, causing powerful stellar winds. Rushing at speeds of more than 150,000 kilometers per hour, these winds carry the outer layers of the star with them, throwing huge volumes of gas and dust into space.

This gas glows with infrared radiation, the same type of light that JWST detects. Astrophysicists have created an impressive image by combining data from two JWST instruments, a near-infrared camera (NIRCam) and a mid-infrared (MIRI) instrument. The Hubble Space Telescope, which predominantly collects light in the optical range, has taken pictures of WR 124 before, but the JWST observations show the star’s growing nebula in stunning new detail.

“Personally, the most exciting part of this image is that we are capturing a rare phenomenon, i.e. a Wolf-Rayet star, at a level of detail that can only be achieved with JWST,” says Macarena Garcia Marin, an astrophysicist. The European Space Agency, which works with MIRI.

Only massive stars can go through the Wolf-Rayet phase, and not all of them. Astronomers have calculated that there are only 1,000 Wolf-Rayet stars in our galaxy—about one in every 100 million. The nearest one is about 1,000 light-years away in the star system Gamma Velorum, visible from the Southern Hemisphere. According to Moffat, Wolf-Rayet stars could be a million times brighter than the Sun. “What they lack in numbers, they make up for in light,” he adds.

“This dust is spreading into space and will eventually create planets. And that’s how we got here, really,” NASA astrophysicist Amber Strone said during a panel discussion at the 2023 South by Southwest conference in Austin, Texas, where the image was first unveiled. “I think this is one of the most beautiful concepts in all of astronomy.”

But while we are all made of stardust, there seems to be a lot more to the universe than scientists can explain with a simple cataloging of obvious sources. “It’s always exciting to be in science when our theories don’t match up with our observations — and that’s where we are right now with the dust,” Strawn says. These detailed pictures of the decoupling of a dying star as it forges heavy elements and produces copious amounts of dust could help scientists refine their understanding of this underlying process.

Someday—thousands or even millions of years from now, but essentially tomorrow on a galactic scale—WR 124 will explode in a spectacular supernova. In addition to a large amount of dust and heavy elements, a black hole may remain after the explosion. But physicists don’t have a good way to predict this with certainty. Moffat suggests that the supernova remnant could instead turn into a neutron star, the last stop before the collapsing star reaches the ultimate oblivion of a black hole. Without a glimpse from some observatory that remains for us in the distant future, we may never know what will happen to WR 124. But in any case, its ultimate fate remains the same, written in stars and planets that are still not formed from his generous gift of cosmic dust.