Thursday, September 26, 2024

 SPACE

 

Webb discovers 'weird' galaxy with gas outshining its stars




Royal Astronomical Society

Galaxy GS-NDG-9422 

image: 

The newly-discovered GS-NDG-9422 galaxy appears as a faint blur in this James Webb Space Telescope NIRCam (Near-Infrared Camera) image. It could help astronomers better understand galaxy evolution in the early Universe.

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Credit: NASA, ESA, CSA, STScI, Alex Cameron (Oxford)





 

The discovery of a "weird" and unprecedented galaxy in the early Universe could "help us understand how the cosmic story began", astronomers say.

GS-NDG-9422 (9422) was found approximately one billion years after the Big Bang and stood out because it has an odd, never-before-seen light signature — indicating that its gas is outshining its stars.

The "totally new phenomena" is significant, researchers say, because it could be the missing-link phase of galactic evolution between the Universe's first stars and familiar, well-established galaxies.

This extreme class of galaxy was spotted by the $10billion (£7.6billion) James Webb Space Telescope (JWST), a joint endeavour of the US, European and Canadian space agencies, which has been designed to peer back in time to the beginning of the Universe.

Its discovery was made public today in a research paper published in the Monthly Notices of the Royal Astronomical Society.

"My first thought in looking at the galaxy's spectrum was, 'that's weird,' which is exactly what the Webb telescope was designed to reveal: totally new phenomena in the early Universe that will help us understand how the cosmic story began," said lead researcher Dr Alex Cameron, of the University of Oxford. 

Cameron reached out to colleague Dr Harley Katz, a theorist, to discuss the strange data. Working together, their team found that computer models of cosmic gas clouds heated by very hot, massive stars, to an extent that the gas shone brighter than the stars, was nearly a perfect match to Webb's observations. 

"It looks like these stars must be much hotter and more massive than what we see in the local Universe, which makes sense because the early Universe was a very different environment," said Katz, of Oxford and the University of Chicago.

In the local Universe, typical hot, massive stars have a temperature ranging between 70,000 to 90,000 degrees Fahrenheit (40,000 to 50,000 degrees Celsius). According to the team, galaxy 9422 has stars hotter than 140,000 degrees Fahrenheit (80,000 degrees Celsius).

The researchers suspect that the galaxy is in the midst of a brief phase of intense star formation inside a cloud of dense gas that is producing a large number of massive, hot stars. The gas cloud is being hit with so many photons of light from the stars that it is shining extremely brightly.

In addition to its novelty, nebular gas outshining stars is intriguing because it is something predicted in the environments of the Universe's first generation of stars, which astronomers classify as Population III stars.

"We know that this galaxy does not have Population III stars, because the Webb data shows too much chemical complexity. However, its stars are different than what we are familiar with – the exotic stars in this galaxy could be a guide for understanding how galaxies transitioned from primordial stars to the types of galaxies we already know," said Katz.

At this point, galaxy 9422 is one example of this phase of galaxy development, so there are still many questions to be answered. Are these conditions common in galaxies at this time period, or a rare occurrence? What more can they tell us about even earlier phases of galaxy evolution?

Cameron, Katz, and their research colleagues are now identifying more galaxies to add to this population to better understand what was happening in the Universe within the first billion years after the Big Bang.

"It's a very exciting time, to be able to use the Webb telescope to explore this time in the Universe that was once inaccessible," Cameron said.

"We are just at the beginning of new discoveries and understanding."

Typical galaxy vs GS-NDG-9422 


Images and captions

Galaxy GS-NDG-9422

Caption: The newly-discovered GS-NDG-9422 galaxy appears as a faint blur in this James Webb Space Telescope NIRCam (Near-Infrared Camera) image. It could help astronomers better understand galaxy evolution in the early Universe. 

Credit: NASA, ESA, CSA, STScI, Alex Cameron (Oxford)

This image of galaxy GS-NDG-9422, captured by the James Webb Space Telescope's NIRCam (Near-Infrared Camera) instrument, is presented with compass arrows, scale bar, and colour key for reference.

Credit

NASA, ESA, CSA, STScI, Alex Cameron (Oxford

Typical galaxy vs GS-NDG-9422

Caption: This comparison of the Webb data with a computer model prediction highlights the same sloping feature that first caught the eye of lead researcher Alex Cameron. The bottom graphic compares what astronomers would expect to see in a "typical" galaxy, with its light coming predominantly from stars (white line), with a theoretical model of light coming from hot nebular gas, outshining stars (yellow line).

Credit: NASA, ESA, CSA, Leah Hustak (STScI)

 

New galaxy with scale bar

Caption: This image of galaxy GS-NDG-9422, captured by the James Webb Space Telescope's NIRCam (Near-Infrared Camera) instrument, is presented with compass arrows, scale bar, and colour key for reference.

Credit: NASA, ESA, CSA, STScI, Alex Cameron (Oxford)

 

Further information

The new study 'Nebular dominated galaxies: insights into the stellar initial mass function at high redshift', Alex J Cameron and Harley Katz et al., has been published in Monthly Notices of the Royal Astronomical Society.

 

Notes for editors

About the Royal Astronomical Society

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

The RAS organises scientific meetings, publishes international research and review journals, recognises outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4,000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The RAS accepts papers for its journals based on the principle of peer review, in which fellow experts on the editorial boards accept the paper as worth considering. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.

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Astronomers catch a glimpse of a uniquely inflated and asymmetric exoplanet



Peer-Reviewed Publication

University of Arizona

Artist's illustration of the exoplanet WASP-107b 

image: 

Artist's illustration of the exoplanet WASP-107 b based on transit observations from NASA's James Webb Space Telescope as well as other space- and ground-based telescopes, led by Matthew Murphy of the University of Arizona and a team of researchers around the world.

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Credit: Rachel Amaro, University of Arizona





Astronomers from the University of Arizona, along with an international group of researchers, observed the atmosphere of a hot and uniquely inflated exoplanet using NASA's James Webb Space Telescope. The exoplanet, which is the size of Jupiter but only a tenth of its mass, is found to have east-west asymmetry in its atmosphere, meaning that there is a significant difference between the two edges of its atmosphere. 

The findings are published in the journal Nature Astronomy. 

"This is the first time the east-west asymmetry of any exoplanet has ever been observed as it transits its star, from space," said lead study author Matthew Murphy, a graduate student at the U of A Steward Observatory. A transit is when a planet passes in front of its star – like the moon does during a solar eclipse. 

"I think observations made from space have a lot of different advantages versus observations that are made from the ground," Murphy said.

East-west asymmetry of an exoplanet refers to differences in atmospheric characteristics, such as temperature or cloud properties, observed between the eastern and western hemispheres of the planet. Determining whether this asymmetry exists or not is crucial for understanding the climate, atmospheric dynamics and weather patterns of exoplanets – planets that exist beyond our solar system. 

The exoplanet WASP-107b is tidally locked to its star. That means that the exoplanet always shows the same face to the star it is orbiting. One hemisphere of the tidally locked exoplanet perpetually faces the star it orbits, while the other hemisphere always faces away, resulting in a permanent day side and a permanent night side of the exoplanet. 

Murphy and his team used the transmission spectroscopy technique with the James Webb Space Telescope. This is the primary tool that astronomers use to gain insights into what makes up the atmospheres of other planets, Murphy said. The telescope took a series of snapshots as the planet passed in front of its host star, encoding information about the planet's atmosphere. Taking advantage of new techniques and the unprecedented precision of the James Webb Space Telescope, the researchers were able to separate the signals of the atmosphere's eastern and western sides and get a more focused look at specific processes happening in the exoplanet's atmosphere. 

"These snapshots tell us a lot about the gases in the exoplanet's atmosphere, the clouds, structure of the atmosphere, the chemistry and how everything changes when receiving different amounts of sunlight," Murphy said. 

The exoplanet WASP-107b is unique in that it has a very low density and relatively low gravity, resulting in an atmosphere that is more inflated than other exoplanets of its mass would be. 

"We don't have anything like it in our own solar system. It is unique, even among the exoplanet population," Murphy said. 

WASP-107b is roughly 890 degrees Fahrenheit – a temperature that is intermediate between the planets of our solar system and the hottest exoplanets known.  

"Traditionally, our observing techniques don't work as well for these intermediate planets, so there's been a lot of exciting open questions that we can finally start to answer," Murphy said. "For example, some of our models told us that a planet like WASP-107b shouldn't have this asymmetry at all – so we're already learning something new."

Researchers have been looking at exoplanets for almost two decades, and many observations from both the ground and space have helped astronomers guess what the atmosphere of exoplanets would look like, said Thomas Beatty, study co-author and an assistant professor of astronomy at the University of Wisconsin-Madison. 

"But this is really the first time that we've seen these types of asymmetries directly in the form of transmission spectroscopy from space, which is the primary way in which we understand what exoplanet atmospheres are made of – it's actually amazing," Beatty said. 

Murphy and his team have been working on the observational data they have gathered and are planning to take a much more detailed look at what's going on with the exoplanet, including additional observations, to understand what drives this asymmetry.

"For almost all exoplanets, we can't even look at them directly, let alone be able to know what's going on one side versus the other," Murphy said. "For the first time, we're able to take a much more localized view of what's going on in an exoplanet's atmosphere."

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