The Hubble Space Telescope has created the largest mosaic image of the Andromeda Galaxy ever made. Located 2.5 million light-years away, it’s our closest major galaxy and can be seen with the naked eye under ideal conditions.
This massive photomosaic is comprised of over 10 years’ worth of data gathered by Hubble and features approximately 200 million stars spread across 2.5 billion pixels. The Andromeda Galaxy holds secrets for astronomers studying its own history and evolution, serving as a proxy for our Milky Way galaxy.
Since we’re embedded within one of the Milky Way’s spiral arms, we can’t observe our entire galaxy. The 200 million detected stars in the Andromeda Galaxy are brighter than our Sun, while estimated trillions of stars remain undetectable by Hubble.
The mosaic was created over two Hubble observing programs: Panchromatic Hubble Andromeda Treasury (PHAT) and Panchromatic Hubble Andromeda Southern Treasury (PHAST). The combined data reveals the galaxy’s age and star masses, shedding light on potential collisions in its past. Notably, satellite galaxy Messier 32 is a candidate for such interactions.
In about 4.5 billion years, the Andromeda Galaxy will collide with our Milky Way, an event predicted by astronomers.
Source: https://www.skyatnightmagazine.com/news/hubble-andromeda-galaxy-mosaic