Early data from the Vera C. Rubin Observatory have revealed two new members of our galaxy’s family. Aquarius IV, found by Yale graduate student William Cerny’s team (Research Notes of the AAS), is an ultra-faint dwarf galaxy more than 350,000 light-years away: a sparse group of ancient, metal-poor stars thought to be held together mostly by dark matter. Rubin-GC1, found by Aashay Pai (University of Chicago) and colleagues (The Astrophysical Journal Letters, 28 Oct), is a globular cluster on the far side of the Milky Way, hidden behind dust towards Ophiuchus. Both come from preview data (April 2025 to January 2026) covering only about 15% of Rubin’s survey area; about 65 Milky Way satellites were known. Caveat: Aquarius IV still needs spectra to be sure it is a galaxy and not a large cluster.
350,000 lydistance of Aquarius IV
~65satellites of the Milky Way known before
~15%of Rubin’s survey area searched so far