The Milky Way is seen above the ESO 3.6-metre telescope at La Silla

The Milky Way and its Galactic Bulge form a bright backdrop for the La Silla Observatory in Chile. Credit: Y. Beletsky (LCO)/ESO

Astronomy and astrophysics

Gigantic stellar cluster may have dwarfish roots

The shape of one of the Milky Way’s largest star clusters hints at independent past.

A cluster of millions of stars may be the remnants of what was once a companion galaxy to the Milky Way.

The stellar cluster, dubbed FSR 1758, is one of the largest ever discovered in our Galaxy. It lies roughly 11,000 parsecs (36,000 light years) from the Solar System in the Milky Way’s bright central bulge and is partially obscured by dust, which makes it difficult to study in detail.

A team led by Rodolfo Barbá at the University of La Serena in Chile identified stars belonging to the cluster by looking for those moving across the sky in a common direction. The researchers’ analysis showed a large arm of stars extending from one side of the cluster, which might be even larger than thought.

Similar extensions are created when gravity tears apart colliding galaxies and flings their stars outwards. FSR 1758’s extension suggests that the cluster could be the stripped remains of a separate dwarf galaxy orbiting the core of the Milky Way.