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The James Webb Space Telescope captured scintillating portraits of 19 spiral galaxies – and the millions of stars that call them home – in unprecedented detail that astronomers have never seen before.
Webb’s unique ability to observe the universe in different wavelengths of infrared light, such as near-infrared and mid-infrared, reveals the stars, gas and dust within the complex structure of each galaxy.
Astronomers believe that about 60% of all galaxies are spiral galaxies – and that our solar system is one of the spiral arms of the Milky Way galaxy. Webb’s observations can help astronomers better understand star formation and the evolution of spiral galaxies like our own.
Seen face-on, each galaxy in the new images has star-filled spiral arms. At the center of every galaxy are clusters of old stars or supermassive black holes.
The observations were made as part of the PHANGS, or Physics at High Angular resolution in Nearby GalaxieS, project. More than 100 astronomers from around the world participate in the program, which also looks at data from the Hubble Space Telescope, the European Space Observatory’s Very Large Telescope MUSE instrument and the Large Atacama Millimeter/submillimeter Array in Chile.
Data from the various telescopes enables astronomers to make observations at different wavelengths of visible, ultraviolet and radio light. Adding Webb’s infrared observations can help address some of the observational gaps.
“Webb’s new images are extraordinary,” Janice Lee, PHANGS core member and project scientist for new missions and strategic initiatives at the Space Telescope Science Institute in Baltimore, said in a statement. “They are amazing even to researchers who have studied these same galaxies for decades. Bubbles and filaments are resolved to the smallest scales ever observed, and tell a story of the star formation cycle.”
Peering inside the spirals
Astronomers used the Webb Near-Infrared Camera to observe millions of stars, visible in sparkling blue, grouped together in clusters and also scattered throughout the arms of 19 galaxies. Meanwhile, the Webb Mid-Infrared Instrument shines a spotlight on the glowing dust surrounding the stars, as well as the red stars that are still forming cocooned in the gas and dust that helps star growth.
“These are the places where we can find the newest and most massive stars in galaxies,” Erik Rosolowsky, a PHANGS core member and professor of physics at the University of Alberta in Edmonton, said in a statement.
The spiral arms are almost incandescent with orange and red gas in Webb’s imagery. The images will be used to help astronomers determine the distribution of gas and dust in spiral galaxies, as well as how galaxies start and stop star formation.
“These structures tend to follow the same pattern in certain parts of the galaxies,” Rosolowsky said. “We think of these as waves, and their spacing tells us a lot about how a galaxy distributes its gas and dust.”
Webb also captured large spherical shell-shaped voids among the gas and galactic dust that are likely to have been sculpted by star explosions.
“These holes may have been created by one or more stars that exploded, carving out giant holes in the interstellar material,” Adam Leroy, a PHANGS core member and professor of astronomy at Ohio State University in Columbus, said in a statement.
Anatomy of a galaxy
Astronomers think that galaxies form from the inside out. Star formation begins at the Galactic center before tearing across the arms in a spiral. That means that a star’s distance from the galactic center is proportional to its age, so younger stars are likely to be further from the galactic center. Groupings of blue stars near the centers of each galaxy indicate older stars.
Meanwhile, some galaxies have pink-red spikes near their centers.
“That’s a clear sign that there might be an active supermassive black hole,” Eva Schinnerer, a PHANGS core member and staff scientist at the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a statement. “Or, the star clusters towards the center are so bright that they saturate that area of the image.”
Scientists are excited to study the vast number of stars revealed by Webb’s new images, according to Leroy.
“Stars can live for billions or trillions of years,” Leroy said. “By precisely cataloging all types of stars, we can build a more reliable, holistic view of their lifetimes.”
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