Vera Rubin Observatory Spots Two New Milky Way Satellites

What else is hiding around our galaxy? Astronomers using the Vera Rubin Observatory have identified two new dim Milky Way satellites. Aquarius IV is a faint, compact system in the outer halo with ancient, metal-poor stars, and it is likely an ultra-faint dwarf galaxy, although a globular cluster has not been ruled out.

The second object, Rubin-GC1, is a dust-shrouded globular cluster near the galactic bulge, about 9.2 billion years old and probably linked to the Sagittarius leading arm. The studies are led by William Cerny of Yale and Aashay Pai of the University of Chicago, with Marla Geha co-authoring both papers. Researchers are excited.

Both discoveries came from Rubin's Early Data Preview 2, released in July, before the main ten-year survey has fully begun. The researchers expect many more satellites to appear as observations continue, which could help scientists test how galaxies like the Milky Way grew and how much dark matter surrounds them.