Astronomers using data from the Euclid space telescope have discovered an exceptionally faint stellar system near the Fornax dwarf galaxy. Named Fornax-7, the system contains only about 170 times the mass of the sun in stars, making it one of the faintest stellar systems ever found.

The discovery paper was posted to the arXiv preprint server on 13 September. Fornax-7 lies about 1.1 degrees from the centre of the Fornax dwarf, corresponding to a projected distance of roughly 2.8 kiloparsecs.

Researchers say it may represent a ‘satellite of a satellite’ – a tiny companion orbiting the Fornax dwarf, which itself orbits the Milky Way. Such a find would extend the observed hierarchy of satellite systems nearly two orders of magnitude below the Large Magellanic Cloud, the current record holder. Alternative explanations include an extremely remote star cluster or an independent ultra-faint dwarf in the Milky Way’s outer halo. Deeper photometric and spectroscopic follow-up will be needed to confirm its nature.