NASA’s James Webb Space Telescope (or JWST) was looking at the first images of a famous old galaxy. Cornell University astronomers noticed another galaxy hiding behind the foreground one that nobody had seen before, and this one is really young – only 1.4 billion years old! But it looks like stars have already formed in it multiple times!
When NASA’s James Webb Space Telescope looked at an early galaxy, Cornell astronomers noticed a bright blob near its edge. The galaxy they were looking at was called SPT0418-47 and it is one of the brightest dusty star-forming galaxies in the universe. Its light was curved and enlarged by another galaxy’s gravity to make a circle shape, which we call an Einstein Ring.
We looked closely at the data from JWST and found a surprise; a small galaxy that was hidden behind another. Even though this galaxy is only 1.4 billion years old, it already has multiple stars in it!
Bo Peng, who is a student studying astronomy, was astonished after discovering the galaxy they studied has surprising amounts of chemicals. He believes that the James Webb Space Telescope will help us understand how stars and galaxies formed in the past.
Peng is the person responsible for writing a new article called “Discovery of a Dusty, Chemically Mature Companion to z~4 Starburst Galaxy in JWST Early Release Science Data,” which was published in the Astrophysical Journal Letters. He didn’t do this alone though; he had 8 people helping him out who are currently studying or have studied Astronomy at College of Arts and Sciences.
The telescope ALMA in Chile had taken pictures showing something weird, but it wasn’t clear what it was. The new JSWT telescope allowed a research associate at Cornell Center for Astrophysics and Planetary Sciences (CCAPS) to see clearly that it was an Einstein ring.
By investigating the spectral data inside every pixel of some images from JWST’s NIRSpec instrument, Peng found an additional source of light within the ring. He figured out that these two new sources were images of a brand-new galaxy which was being magnified by the same foreground galaxy causing the ring. These two images were even fainter than we thought before, but this shows how well JWST is able to see things in infrared vision.
We studied the chemical makeup of the light and noticed that hydrogen, nitrogen, and sulfur atoms all had redshifts- meaning their light had become more reddish. This told us these two galaxies were both very far away from Earth since redshift increases with distance from us. We measured the redshift to be 4.2 which means these galaxies are approximately 10% of the universe’s age away from us!
To make sure their discovery was true, the researchers checked what they found using earlier observations from ALMA. They discovered an emission line of an ionized form of carbon that perfectly matched the same redshifts seen by JWST.
“This really confirmed it,” Vishwas said. “Because we saw several emissions lines had been shifted in exactly the same way, we are certain this galaxy is actually where we think it should be.”
The team did measurements and figured out that the other galaxy (named SPT0418-SE) is very close to the ring. It’s only 5 kilometers away, while the two galaxies around our Milky Way, which are called the Magellanic Clouds, are about 50 kilometers away from us. This means these two galaxies could interact with each other and might even become one in future – something that could help us understand how small galaxies become bigger ones.
The two galaxies are not very big when you compare them to other galaxies from the early universe. The one known as “SE” is even smaller, and it doesn’t have much dust, making it look bluer than the ring that is covered in a lot of dust. After looking at images of close-by galaxies with similar colors, the researchers think that they might be located in a massive halo made up of dark matter which we have yet to discover.
The researchers found something unusual in galaxies that are relatively young and lightweight—they contained a large amount of “metals”. Metals are elements other than helium and hydrogen, such as carbon, oxygen and nitrogen. In fact, the metal levels were almost similar to our sun’s. The sun is 4 billion years old, while these galaxies were less than 1.5 billion years old. So it’s amazing how much metals they had built up in such a short period of time.
Vishwas said it’s unusual to find stars that have been around for a long time, like from the first billion years of the universe. We think these galaxies had lots of stars being made quickly, which helps explain why there is so much nitrogen compared to oxygen. That ratio is how we know how many generations of stars have lived and died.
Scientists have asked for permission to use the James Webb Space Telescope to study a spiral-shaped galaxy and its stars. The purpose of this research is to figure out why people can see it differently in optical and far-infrared light.
“We still have to study this galaxy,” said Peng, one of the scientists on the project. “The data gives us more things to discover.”
In February 2023, a group of scientists published a paper about their discovery of a chemical-filled dusty companion to a starburst galaxy located at the far corner of the universe. According to this paper, named “Discovery of a Dusty, Chemically Mature Companion to a z ∼ 4 Starburst Galaxy in JWST ERS Data”, this chemical-filled companion is believed to be formed by the combination of galactic interactions and matter redistribution within the starburst galaxy.
The team thanked the program that made it possible for the public to access new data from the James Webb Space Telescope (JWST). This program is called TEMPLATES and led by NASA scientist Jane Rigby. It helps us see faraway objects with extreme magnification.
Peng and Vishwas, who wrote the research paper, had help from seven other people: Thomas Nikola (a research associate at a certain place called CCAPS), Gordon Stacey (a professor of astronomy who graduated in 1985), Catie Ball and Christopher Rooney (both doctoral students), Henrik Spoon (a visiting scientist at CCAPS and librarian at Cornell University Library’s Clark Physical Sciences Library), Carl Ferkinhoff (an associate professor of Physics with a Ph.D. from 2014) and Cody Lamarche (an adjunct professor of Physics who earned his Ph.D. in 2019). The research work was supported by the National Science Foundation.
