Hubblei

Hubblei is a hypothetical ultra-faint dwarf galaxy used in astronomy education to illustrate the properties of low-luminosity satellite systems around larger galaxies. The name honors the Hubble Space Telescope, reflecting the role of high-resolution imaging in identifying faint stellar companions.

In the hypothetical scenario, Hubblei would inhabit the outskirts of the Milky Way, at a distance of roughly 60 to 150 kiloparsecs from the Sun. It would have a very low luminosity, with an absolute magnitude around −4 to −6, and a half-light radius of a few tens to a couple hundred parsecs, placing it among the smallest known dwarf galaxies.

Its stellar population would be predominantly old and metal-poor, with a broad distribution of metallicities indicating a limited and truncated star-formation history preceding quenching.

Kinematic and chemical studies in such systems typically rely on spectroscopic measurements of resolved stars, using velocity dispersions of a few kilometers per second to infer dark matter dominance. In Hubblei, as in real ultra-faint dwarfs, dark matter is inferred to dominate the mass budget, yielding high mass-to-light ratios.

Observational methods would include deep wide-field imaging to detect faint stellar overdensities, followed by spectroscopy to confirm member stars and measure dynamics. While Hubblei is a pedagogical construct, the study of real ultra-faint dwarfs informs models of galaxy formation and the nature of dark matter.