The Andromeda galaxy, also known as Messier 31 (M31), is the closest spiral galaxy to the Milky Way at a distance of about 2.5 million light-years. Astronomers use Andromeda to understand the structure and evolution of our own spiral, which is much harder to do since Earth is embedded inside the Milky Way.
The galaxy M31 has played an important
role in many aspects of astrophysics, but particularly in the discovery of dark matter. In the 1960s, astronomer Vera Rubin and her colleagues studied M31 and
determined that there was some unseen matter in the galaxy that was affecting
how the galaxy and its spiral arms rotated. This unknown material was named
“dark matter.” Its nature remains one of the biggest open questions in
astrophysics today, one which NASA’s upcoming Nancy Grace Roman Space Telescope
is designed to help answer.
X-ray: NASA/CXO/UMass/Z. Li &
Q.D. Wang, ESA/XMM-Newton; Infrared: NASA/JPL-Caltech/WISE, Spitzer,
NASA/JPL-Caltech/K. Gordon (U. Az), ESA/Herschel, ESA/Planck, NASA/IRAS,
NASA/COBE; Radio: NSF/GBT/WSRT/IRAM/C. Clark (STScI); Ultraviolet: NASA/JPL-Caltech/GALEX;
Optical: Andromeda, Unexpected © Marcel Drechsler, Xavier Strottner, Yann
Sainty & J. Sahner, T. Kottary. Composite
image processing: L. Frattare, K. Arcand, J.Major
This new composite image contains data of M31 taken by some of the world’s
most powerful telescopes in different
kinds of light. This image includes X-rays from NASA’s Chandra X-ray Observatory and ESA’s (European Space Agency’s) XMM-Newton
(represented in red, green, and blue); ultraviolet data from NASA’s retired
GALEX (blue); optical data from astrophotographers using ground based
telescopes (Jakob Sahner and Tarun Kottary); infrared data from NASA’s retired
Spitzer Space Telescope, the Infrared Astronomy Satellite, COBE, Planck, and
Herschel (red, orange, and purple); and radio data from the Westerbork
Synthesis Radio Telescope (red-orange).
The Andromeda Galaxy (M31) in Different Types of
Light.
X-ray: NASA/CXO/UMass/Z. Li & Q.D. Wang,
ESA/XMM-Newton; Infrared: NASA/JPL-Caltech/WISE, Spitzer, NASA/JPL-Caltech/K.
Gordon (U. Az), ESA/Herschel, ESA/Planck, NASA/IRAS, NASA/COBE; Radio:
NSF/GBT/WSRT/IRAM/C. Clark (STScI); Ultraviolet: NASA/JPL-Caltech/GALEX;
Optical: Andromeda, Unexpected © Marcel Drechsler, Xavier Strottner, Yann
Sainty & J. Sahner, T. Kottary. Composite image processing: L. Frattare, K.
Arcand, J.Major
Each type of light reveals new information about this close galactic
relative to the Milky Way. For example, Chandra’s X-rays reveal the high-energy
radiation around the supermassive black hole at the center of M31 as well as many other
smaller compact and dense objects strewn across the galaxy. A recent paper
about Chandra observations of M31 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.
These multi-wavelength datasets are
also being released as a sonification, which includes the same wavelengths of
data in the new composite. In the sonification, the layer from each telescope
has been separated out and rotated so that they stack on top of each other
horizontally, beginning with X-rays at the top and then moving through
ultraviolet, optical, infrared, and radio at the bottom. As the scan moves from
left to right in the sonification, each type of light is mapped to a different
range of notes, from lower-energy radio waves up through the high energy of
X-rays. Meanwhile, the brightness of each source controls volume, and the
vertical location dictates the pitch.
In this sonification of M31, the layers from each
telescope has been separated out and rotated so that they stack on top of each
other horizontally beginning with X-rays at the top and then moving through
ultraviolet, optical, infrared, and radio at the bottom. As the scan moves from
left to right in the sonification, each type of light is mapped to a different
range of notes ranging from lower-energy radio waves up through the high-energy
of X-rays. Meanwhile, the brightness of each source controls volume and the
vertical location dictates the pitch.
NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A.
Santaguida
This new image of M31 is released in tribute to the groundbreaking legacy
of Dr. Vera Rubin, whose observations transformed our understanding of the
universe. 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.
NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Source: NASA's Chandra Shares a New View of Our Galactic Neighbor - NASA
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