NASA has released the clearest and most detailed image ever obtained of the Andromeda Galaxy, the neighbor of the Milky Way. The new image is not only a visual achievement; we can say that it is also the product of a multidisciplinary scientific study aimed at solving the dark secrets of the universe.
Andromeda Galaxy, very clearly imaged
This composite image prepared in memory of Vera C. Rubin, who left her mark on astronomy history, focuses on the galaxy where the first direct observations indicating the existence of dark matter were made.
This detailed imaging of Andromeda was made possible by combining data collected by NASA’s Chandra X-ray telescope, as well as the European Space Agency’s XMM-Newton mission, the retired Spitzer and GALEX telescopes, cosmic observation instruments such as COBE, Planck, Herschel, and ground-based systems such as the Westerbork Radio Telescope. Observations made at different wavelengths revealed the galaxy’s multi-layered and rich structure with unprecedented clarity.
In particular, Chandra’s X-ray observations show high-energy radiation emanating from the supermassive black hole M31* at the center of the galaxy. This black hole is much larger than Sagittarius A* at the center of the Milky Way.
Sagittarius A* has a mass of about 4.3 million times that of the Sun, while M31* has a mass of 100 million times that of the Sun. This explains why the black hole in Andromeda occasionally draws attention with its energetic X-ray flares. In comparison, Sagittarius A* is much more static.
Andromeda was chosen not only for its proximity. This galaxy, which is 2.5 million light-years away, made history in astronomy with the studies conducted by Vera Rubin and her team in the 1960s. Rubin’s observations revealed that Andromeda’s spiral arms were rotating much faster than they should be.
Despite these speeds, the fact that the galaxy did not disperse showed that it was gravitationally held by an invisible substance surrounding it. This invisible structure was called dark matter, and these observations were accepted as the first strong evidence for its existence.
This finding is not unique to Andromeda. Later studies revealed that all large galaxies in the universe are similarly surrounded by dark matter. Observable stars, gases, and planets make up only about 15% of the total matter in the universe. The remaining large portion consists of dark matter, which cannot be directly seen and can only be detected through its gravitational effects.
The new image of Andromeda provides an important resource to better understand the effects of this unknown structure on the formation and structure of galaxies. It also serves as a reference point for dark matter theories that push the boundaries of particle physics. The scientific legacy initiated by Rubin is once again on the agenda with this new observation, while continuing to seek new answers to questions about the unseen side of the universe.
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