James Webb Space Telescope peers into lonely dwarf galaxy
The most powerful space telescope currently in operation has zoomed in on a solitary dwarf galaxy in our galactic environment, imaging it in stunning detail.
The dwarf is about 3 million light-years from Earth universenamed Wolf-Lundmark-Melotte (WLM) for three astronomers who were instrumental in its discovery, is close enough that the James Webb Space Telescope (JWST) can distinguish individual stars yet large numbers stars at the same time. The dwarf galaxy, in the constellation Cetus, is one of the most distant members of the local galaxy group that contains our galaxy. Its isolated nature and lack of interaction with other galaxies, including the Milky Waymake WLM useful in studying how stars evolve in smaller galaxies.
“We don’t think WLM has interacted with other systems, which makes it a lot of fun to test our theories about galaxy formation and evolution,” said Kristen McQuinn, an astronomer at Rutgers University in New Jersey and lead scientist on the research project. , in a pronunciation of the Space Telescope Science Institute in Maryland, which operates the observatory. “Many of the other nearby galaxies are intertwined and entwined with the Milky Way, making them more difficult to study.”
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McQuinn pointed to a second reason why WLM is an intriguing target: Its gas is very similar to that of galaxies in the early Universe, without elements heavier than hydrogen and helium.
But while the gas from those early galaxies never contained heavier elements, the gas in WLM has lost its share of these elements due to a phenomenon called galactic winds. These winds arise from supernovae or exploding stars; because WLM has so little mass, these winds can push material out of the dwarf galaxy.
In WLM’s JWST image, McQuinn described a series of individual stars at different points in their evolution with a variety of colors, sizes, temperatures and ages. The image also shows clouds of molecular gas and dust called nebulae, which contain the raw material for star formation within WLM. In background galaxies, JWST can see fascinating features such as massive tidal tails, which are structures made of stars, dust and gas created by gravitational interactions between galaxies.
The main goal of JWST in studying WLM is to reconstruct the star birth history of the dwarf galaxy. “Low-mass stars can live for billions of years, meaning some of the stars we see in WLM today were formed in the early universe,” McQuinn said. “By determining the properties of these low-mass stars (such as their ages), we can gain insight into what happened in the very distant past.”
The work complements the study of galaxies in the early Universe that JWST already facilitates, and it also allows telescope operators to perform calibration of the NIRCam Instrument who captured the sparkling image. That’s possible because both the Hubble Space Telescope and the now-retired Spitzer Space Telescope have studied the dwarf galaxy before and scientists can compare the images.
“We use WLM as a sort of standard for comparison to help us understand the JWST observations,” McQuinn said. “We want to make sure that we measure the brightness of the stars really, very accurately and precisely. We also want to make sure that we understand our stellar evolution models in the near infrared.”
McQuinn’s team is currently developing a software tool that anyone can use that can measure the brightness of all individually resolved stars in the NIRCam images, she said.
“This is a fundamental tool for astronomers around the world,” she said. “If you want to do something with dissolved stars crammed together in the sky, you need a tool like this.”
The team’s WLM study is currently awaiting peer review.
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