Check Out the Hubble Space Telescope’s Stunning New View of the Andromeda Galaxy

Margherita Bassi

Daily Correspondent

NASA’s Earth-orbiting Hubble Space Telescope has just released the most comprehensive astronomical survey of Andromeda, the closest galaxy to the Milky Way. The resulting colossal image was stitched together from 600 different fields of view, is made of at least 2.5 billion pixels and took more than a decade to create.

Presented last week at a meeting of the American Astronomical Society and published in The Astrophysical Journal, the new “photomosaic” also sheds light on our neighboring galaxy’s evolutionary history.

“One of Hubble’s lasting achievements will be how it showed the public the wonders of the universe,” Kenneth Sembach, an astronomer at the Space Telescope Science Institute, told National Geographic’s Daniel Stone in 2020. His remark holds true now, nearly half a decade later.

At 2.5 million light-years away, the Andromeda Galaxy—officially called Messier 31—is the farthest object visible to the naked eye. It appears as a fuzzy cigar shape in the sky on clear and dark nights.

The photographic mosaic was achieved thanks to the efforts of two Hubble programs that spanned more than ten years and over 1,000 orbits around Earth. The Panchromatic Hubble Andromeda Treasury captured the northern half of the galaxy, while the following Panchromatic Hubble Andromeda Southern Treasury imaged the southern half. The final image displays the galaxy tilted at a 77-degree angle relative to how we see it from Earth.

“With Hubble, we can get into enormous detail about what’s happening on a holistic scale across the entire disk of the [Andromeda] galaxy. You can’t do that with any other large galaxy,” Benjamin Williams, an astronomer at the University of Washington and principal investigator for the project, says in a statement.

In fact, the image could reveal clues about Andromeda’s history, which might include past mergers of galaxies and close galactic encounters.

“Andromeda’s a train wreck. It looks like it has been through some kind of event that caused it to form a lot of stars and then just shut down,” Daniel Weisz, an astronomer at the University of California, Berkeley, says in a statement from NASA. “This was probably due to a collision with another galaxy in the neighborhood.”

“This detailed look at the resolved stars will help us to piece together the galaxy’s past merger and interaction history,” Williams adds.

Hubble, however, has its limits—the space telescope can only detect stars brighter than our sun. In the image of Andromeda, it pinpointed more than 200 million stars—but that’s still much less than the one trillion stars that astronomers suggest make up the galaxy’s stellar population.

Still, observation of Andromeda has come a long way. Roughly 100 years ago, our neighboring spiral galaxy was discovered by American astronomer Edwin Hubble. Previously, scientists thought the entire universe existed within the Milky Way, per the NASA statement. But when Andromeda proved to be its very own galaxy, astronomers realized the universe was much, much larger than they’d anticipated.

2.5 Billion Pixel Image of Galaxy Shot by Hubble

Just like the recent Andromeda news, Edwin Hubble’s discovery was officially announced at an American Astronomical Society meeting, in January 1925. The astronomer, however, had leaked the information to the New York Times in November of the previous year, according to Space.com’s Keith Cooper, so the scientific community—as well as the rest of the world—was already buzzing with excitement.

“One hundred years is not that far away,” Jeff Rich, an astronomer at the Carnegie Science Observatories, said during the recent American Astronomical Society meeting, per Space.com. “This is really a lesson of how much things have changed and how discoveries can come at us fast.”

Likewise, this photomosaic of Andromeda likely isn’t an ending, but the start of another century of astronomical insight. With NASA’s James Webb Space Telescope and the upcoming Nancy Grace Roman Space Telescope, future observations can reveal even more about our breathtaking cosmic neighbor.