Using data from several space- and ground-based telescopes, NASA astronomers have captured a stunning new image of the Andromeda galaxy, which is the closest spiral galaxy to the Milky Way.
This new composite image of the Andromeda galaxy includes X-rays from Chandra and XMM-Newton (represented in red, green, and blue); ultraviolet data from GALEX (blue); optical data from astrophotographers using ground based telescopes (Jakob Sahner and Tarun Kottary); infrared data from Spitzer, the Infrared Astronomy Satellite, COBE, Planck, and Herschel (red, orange, and purple); and radio data from the Westerbork Synthesis Radio Telescope (red-orange). Image credit: NASA.
The Andromeda galaxy, also known as NGC 224, Messier 31 or M31, is a spiral galaxy approximately 2.5 million light-years away.
It contains over 100 billion stars and is comparable in size to our Milky Way Galaxy.
It can be seen as a cigar-shaped smudge of light high in the autumn sky. But if you could see the huge bubble of hot, diffuse plasma surrounding the galaxy, it would appear 100 times the angular diameter of the full Moon.
Andromeda’s dark, nearly invisible halo stretches about a million light-years from the galaxy, halfway to our home Galaxy, and is estimated to contain half the mass of the stars in the galaxy itself.
The Andromeda galaxy has played an important role in many aspects of astrophysics, but particularly in the discovery of dark matter.
In the 1960s, astronomer Dr. Vera Rubin and her colleagues studied the Andromeda and determined that there was some unseen matter in the galaxy that was affecting how the galaxy and its spiral arms rotated.
“This new image of the Andromeda galaxy is released in tribute to the groundbreaking legacy of Vera Rubin, whose observations transformed our understanding of the Universe,” NASA astronomers said in a statement.
“Rubin’s meticulous measurements of Andromeda’s rotation curve provided some of the earliest and most convincing evidence that galaxies are embedded in massive halos of invisible material — what we now call dark matter.”
“Her work challenged long-held assumptions and catalyzed a new era of research into the composition and dynamics of the cosmos.”
“In recognition of her profound scientific contributions, the United States Mint has recently released a quarter in 2025 featuring Rubin as part of its American Women Quarters Program — making her the first astronomer honored in the series.”
To create the new image of the Andromeda galaxy, the astronomers used data from NASA’s Chandra X-ray Observatory; ESA’s XMM-Newton, Planck, and Herschel telescopes, NASA’s retired GALEX and Spitzer telescopes; data from astrophotographers using ground based telescopes; radio data from the Westerbork Synthesis Radio Telescope.
“Each type of light reveals new information about this close galactic relative to the Milky Way,” researchers said.
“For example, Chandra’s X-rays reveal the high-energy radiation around the supermassive black hole at the center of the Andromeda galaxy as well as many other smaller compact and dense objects strewn across the galaxy.”
“A recent paper about Chandra observations of the Andromeda galaxy discusses the amount of X-rays produced by the supermassive black hole in the center of the galaxy over the last 15 years.”
“One flare was observed in 2013, which appears to represent an amplification of the typical X-rays seen from the black hole.”
