The James Webb Space Telescope’s Early Release Science (ERS) program – first released on July 12, 2022 – has proven to be a treasure trove of scientific findings and discoveries.
Among the many areas of research it enables is the study of Resolved Stellar Populations (RSTs), which was the subject of ERS 1334.
This refers to large groups of stars close enough that individual stars can be distinguished but far enough apart that telescopes can capture many of them at once. A good example is the Wolf-Lundmark-Melotte (WLM) dwarf galaxy neighboring the Milky Way.
Kristen McQuinn, assistant professor of astrophysics at Rutgers University, is one of the lead scientists of the Webb ERS program whose work focuses on RST. He recently spoke with NASA senior communications specialist Natasha Piro about how JWST has enabled new studies of the WLM.
Webb’s improved observations revealed that this galaxy has not interacted with other galaxies in the past.
According to McQuinn, this makes it an excellent candidate for astronomers to test theories of galaxy formation and evolution. Here are the highlights of that interview.
The WLM is about 3 million light-years from Earth, which means it is quite close (in astronomical terms) to the Milky Way. However, it is also relatively isolated, leading astronomers to conclude that it has not interacted with other systems in the past.
When astronomers observed other nearby dwarf galaxies, they noticed that they are usually entangled with the Milky Way, indicating that they are in the process of merging.
This makes them more difficult to study, as the population of stars and gas clouds cannot be fully distinguished from our own.
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Another important thing about the WLM is that it is low in elements heavier than hydrogen and helium (which were very common in the early Universe). Elements such as carbon, oxygen, silicon, and iron formed in the cores of early population stars and were dispersed when those stars exploded in supernovae.
In the case of the WLM, which has experienced star formation throughout its history, the force of these explosions has pushed these elements out over time. This process is known as “galactic winds” and has been observed with small, low-mass galaxies.
The new Webb images provide the clearest view of the WLM ever seen. Previously, the dwarf galaxy was imaged by the Infrared Array Camera (IAC) on the Spitzer Space Telescope (SST).
These provided limited resolution compared to the Webb images, which can be seen in the side-by-side comparison (shown below).
As you can see, Webb’s infrared optics and advanced suite of instruments provide a much deeper view that allows differentiation of individual stars and features. As McQuinn described it:
“We can see myriads 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 diffraction peaks, and background galaxies with neat features such as tidal tails. It’s really a great picture.”
The ERS program
As McQuinn explained, the main scientific focus of ERS 1334 is to build on previous expertise developed with Spitzer, Hubble and other space telescopes to learn more about the star formation history of galaxies.
Specifically, they are conducting deep multi-band imaging of three analyzed star systems within a Megaparsec (~3,260 light-years) from Earth using Webb’s Near-Infrared Camera (NIRCam) and the Near-Infrared Imaging Slitless Spectrograph (NIRISS).
These include the globular cluster M92, the extremely faint dwarf galaxy Draco II, and the star-forming dwarf galaxy WLM.
The population of low-mass stars in the WLM makes it particularly interesting because they are so long-lived, meaning that some of the stars seen there today may have formed during the early Universe.
“By determining the properties of these low-mass stars (as well as their ages), we can gain insight into what was happening in the very distant past,” McQuinn said.
“It’s very complementary to what we’re learning about early galaxy formation by looking at high-redshift systems, where we see galaxies as they were when they first formed.”
Another goal is to use the WLM dwarf galaxy to calibrate JWST to ensure it can measure the brightness of stars with extreme precision, which will allow astronomers to test models of stellar evolution in the near-infrared.
McQuinn and her colleagues are also developing and testing non-proprietary software to measure the brightness of analyzed stars imaged with NIRCam, which will be available to the public.
The results of the ESR project will be made public before the call for proposals for Round 2 (January 27, 2023).
The James Webb Space Telescope has been in space for less than a year, but it has already proven invaluable. The stunning views of the universe it has provided include deep-field images, extremely precise observations of galaxies and nebulae, and detailed spectra of exoplanet atmospheres.
The scientific discoveries it has already enabled have been nothing short of groundbreaking. Before its planned 10-year mission (which could be extended to 20) is completed, some truly paradigm-changing discoveries are expected.
This article was originally published by Universe Today. Read the original article.