The most powerful space telescope currently in operation has zoomed in on a lone dwarf galaxy in our galactic neighborhood, imaging it in stunning detail.
About 3 million light-years from Earth, the dwarf galaxynamed Wolf–Lundmark–Melotte (WLM) after three astronomers who contributed to its discovery, is close enough that James Webb Space Telescope (JWST) can distinguish individual stars while being able to study a large number of stars simultaneously. The dwarf galaxy, in the constellation of Cetus, is one of the outermost members of the group of local galaxies that contains our galaxy. Its isolated nature and lack of interactions with other galaxies, including the Milky Waymake the WLM useful in studying the evolution of stars in smaller galaxies.
“We think WLM hasn’t interacted with other systems, which makes it really nice to test our theories about galaxy formation and evolution,” said Kristen McQuinn, an astronomer at Rutgers University in the New Jersey and lead scientist of the research project. statement from the Space Telescope Science Institute of Maryland, which operates the observatory. “Many other nearby galaxies are intertwined and entangled 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, with no elements heavier than hydrogen and helium.
But while the gas in those early galaxies never contained heavier elements, WLM gas lost its share of those elements to a phenomenon called galactic winds. These winds come 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 seeing an array 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 in the WLM. In background galaxies, JWST can spot fascinating features such as massive tidal tails, which are structures made of stars, dust, and gas created by gravitational interactions between galaxies.
The main objective of the JWST in the study of the WLM is to reconstruct the history of the birth of stars in the dwarf galaxy. “Low-mass stars can live for billions of years, which means some of the stars we see in the WLM today formed in the early universe,” McQuinn said. “By determining the properties of these low-mass stars (like their age), we can better understand 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 verify the calibration of the NIR Cam Instrument who captured the sparkling image. That’s possible because the Hubble Space Telescope and the now-retired Spitzer Space Telescope have previously studied the dwarf galaxy, and scientists can compare images.
“We use WLM as a sort of standard for comparison to help us make sure we understand the JWST observations,” McQuinn said. “We want to make sure that we’re measuring the brightness of stars really, really accurately and precisely. We also want to make sure that we understand our patterns of near-infrared stellar evolution.”
McQuinn’s team is currently developing a software tool that anyone can use that can measure the brightness of all individually resolved stars in NIRCam images, she said.
“This is a fundamental tool for astronomers around the world,” she said. “If you want to do anything with resolute stars that are piled up in the sky, you need a tool like this.”
The team’s WLM research is currently awaiting peer review.
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