The new image of the dwarf irregular galaxy Wolf-Lundmark-Melotte demonstrates the remarkable ability of the NASA/ESA/CSA James Webb Space Telescope to resolve faint stars outside the Milky Way.
This image, taken by the Near-Infrared Camera aboard the NASA/ESA/CSA James Webb Space Telescope, displays countless stars in the dwarf irregular galaxy Wolf-Lundmark-Melotte as well as dozens of background galaxies. The image includes 0.9-micron light shown in blue, 1.5-micron in cyan, 2.5-micron in yellow, and 4.3-micron in red. Image credit: NASA / ESA / CSA / STScI / K. McQuinn, Rutgers University / A. Pagan, STScI.
Wolf-Lundmark-Melotte (WLM for short) is located approximately 3.1 million light-years away in the constellation of Cetus.
This galaxy was first discovered in 1909 by the German astronomer Max Wolf. But its nature as a galaxy was only established in 1926 by astronomers Knut Lundmark and Philibert Jacques Melotte.
Also known as DDO 221 and LEDA 143, WLM spans about 8,000 light-years at its greatest extent, a measurement that includes a halo of extremely old stars discovered in 1996.
Although considered part of Local Group of galaxies (the collection of galaxies that includes the Milky Way, the Magellanic Clouds, Andromeda, M33, and dozens of smaller galaxies), WLM stands alone at the group’s outer edges as one of its most remote members.
In fact, the galaxy is so small and secluded that it may never have interacted with any other Local Group galaxy — or perhaps even any other galaxy in the history of the Universe.
“WLM is a dwarf galaxy in our galactic neighborhood. It’s fairly close to the Milky Way, but it’s also relatively isolated,” said Dr. Kristen McQuinn, an astronomer at Rutgers University.
“We think WLM hasn’t interacted with other systems, which makes it really nice for testing our theories of galaxy formation and evolution.”
“Many of the other nearby galaxies are intertwined and entangled with the Milky Way, which makes them harder to study.”
“Another interesting and important thing about WLM is that its gas is similar to the gas that made up galaxies in the early Universe. It’s fairly unenriched, chemically speaking.”
“This is because the galaxy has lost many of these elements through something we call galactic winds.”
“Although WLM has been forming stars recently — throughout cosmic time, really — and those stars have been synthesizing new elements, some of the material gets expelled from the galaxy when the massive stars explode.”
“Supernovae can be powerful and energetic enough to push material out of small, low-mass galaxies like WLM.”
“This makes WLM super interesting in that you can use it to study how stars form and evolve in small galaxies like those in the ancient Universe.”
The new image of the WLM galaxy was taken as part of Webb’s Early Release Science (ERS) program 1334, focused on resolved stellar populations.
“We can see a myriad of individual stars of different colors, sizes, temperatures, ages, and stages of evolution; interesting clouds of nebular gas within the galaxy; foreground stars with Webb’s diffraction spikes; and background galaxies with neat features like tidal tails. It’s really a gorgeous image,” Dr. McQuinn said.
“And, of course, the view is far deeper and better than our eyes could possibly see. Even if you were looking out from a planet in the middle of this galaxy, and even if you could see infrared light, you would need bionic eyes to be able to see what Webb sees.”
“The main science focus is to reconstruct the star formation history of this galaxy,” she added.
“Low-mass stars can live for billions of years, which means that some of the stars that we see in WLM today formed in the early Universe.”
“By determining the properties of these low-mass stars (like their ages), we can gain insight into what was happening in the very distant past.”
“It’s very complementary to what we learn about the early formation of galaxies by looking at high-redshift systems, where we see the galaxies as they existed when they first formed.”
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