It may be a “train wreck,” in the words of astronomer Dan Weisz, but it’s a beautiful train wreck.
Weisz, an associate professor of astronomy at the University of California, Berkeley, is referring to the Andromeda galaxy, the nearest large galaxy to our own Milky Way and the closest one that astronomers can study for clues to our galaxy’s evolution.
A mosaic image of the entire Andromeda galaxy (Messier 31, or M31), 2.5 million light years away but six times larger than the moon in the night sky, was released today (Jan. 16) by the Space Telescope Science Institute in Maryland. The galaxy’s brilliant yellow center is surrounded by an ethereal blue luminescence, the stars like grains of sand on a beach.
The new image contains 2.5 billion pixels and was produced from about 600 images taken by NASA’s Hubble Space Telescope over the past 10 years. Stitched into a single image, the mosaic would cover about 75 8K ultra-high-definition video screens.
What it reveals, Weisz says, is that the galaxy has collided with another galaxy over the past 5 billion years, leaving behind trails of star formation that astronomers can use to trace these collisions into the past. Weisz was a co-principal investigator on the first part of the Andromeda survey, the Panchromatic Hubble Andromeda Treasury (PHAT) program, which produced a hi-resolution image of the galaxy’s northern half in 2015. He is a co-investigator on the second and final phase, the Panchromatic Hubble Andromeda Southern Treasury (PHAST). The mosaic of the combined images was unveiled at the annual meeting of the American Astronomical Society in National Harbor, Maryland.