Exploring Andromeda’s past through Nasa’s Hubble Space telescope

Since Hubble’s launch, astronomers have discovered over 1 trillion galaxies, but Andromeda stands out as the closest and most significant to our Milky Way. Visible to the naked eye on clear autumn nights, it appears as a faint, cigar-shaped object, roughly the size of the Moon in the sky. (Image credits: Nasa)

A century ago, Edwin Hubble revealed that the "spiral nebula" was not part of our Milky Way but located 2.5 million light-years away, about 25 times the Milky Way's diameter. Before this discovery, astronomers believed the Milky Way was the entire universe. Hubble's findings reshaped cosmology, revealing a vastly larger cosmos. (Image credits: Nasa)

Photographing Andromeda was a monumental challenge due to its vast size, far exceeding the galaxies Hubble usually observes. The full mosaic was completed across two Hubble programs, requiring over 1,000 orbits and more than a decade of work to capture the galaxy's intricate details. (Image credits: Nasa)

The Panchromatic Hubble Andromeda Southern Treasury (PHAST), led by Zhuo Chen, added images of 100 million stars in Andromeda's southern half. This region provides key insights into the galaxy's merger history, offering a deeper understanding than the northern disk mapped by the PHAT survey. (Image credits: Nasa)

The Hubble survey programs offer critical data on Andromeda's age, element abundance, and stellar masses, helping astronomers distinguish between different merger scenarios. These detailed measurements from Hubble refine models of Andromeda’s merger history and disk evolution, shedding light on the galaxy’s complex past. (Image credits: Nasa)

In addition to these stellar streams, Hubble’s detailed imaging has allowed scientists to study the star populations in Andromeda. By examining these stars, scientists gain insights into the galaxy’s age, structure, and its long evolutionary journey. (Image credits: Nasa)

Although the Milky Way and Andromeda likely formed around the same time billions of years ago, they have distinct evolutionary paths. Andromeda is populated with younger stars and unique features, such as coherent stellar streams, suggesting it has experienced more active recent star formation and cosmic interactions compared to the Milky Way. (Image credits: Nasa)