| Leo P | |
|---|---|
 Leo P byHubble Space Telescope | |
| Observation data (J2000epoch) | |
| Constellation | Leo |
| Right ascension | 10h 21m 45.123s[1] |
| Declination | +18° 05′ 16.89″[1] |
| Distance | 5,284kly (1,620kpc)[2] |
| Group orcluster | Antlia Sextans Group |
| Apparent magnitude (V) | 16.89[3] |
| Absolute magnitude (V) | −9.27[2] |
| Characteristics | |
| Type | Irr |
| Size | 1132 pc[4] (3692.09 ly) |
| Apparent size (V) | 1.2′[2] |
| Other designations | |
| Leo P,[1] AGC 208583 | |
Leo P is a small, star-formingirregular galaxy located in the constellationLeo, discovered through the blind HI Arecibo Legacy Fast ALFA (ALFALFA) survey, as an ultra-compact high-velocity cloud (UCHVC) of hydrogen gas. Its confirmation as adwarf galaxy in 2013 suggests that other such UCHVCs are possibly undiscovered dwarf galaxies themselves.[5] Leo P is noteworthy for harbouring one of the most metal-poor environments in the local universe. Its metallicity is just 3% that of the Sun's, meaning that its stars contain 30 times less heavy elements than the Sun.[2] This makes Leo P similar to the pristine environments of primordial galaxies.
Leo P is located on the very outskirts of theLocal Group, nearly 5.3 million light years away, and may not be part of it, instead being part of theAntlia-Sextans Group, a small grouping of galaxies adjacent to the Local Group, sometimes considered bound to it.
Leo P is one of the smallest, least massive and faintest star-forming galaxies in theLocal Group. Its total luminosity is less than 440,000 times that of the Sun (absolute magnitude of −9.27), and its stellar mass is only about 560,000solar masses, implying a small stellar population. Leo P is also very rich in gas, containing about 810,000 solar masses of neutral hydrogen.[2] Leo P'shalf-light radius is about 570 pc.[4] Early attempts to detectmolecular hydrogen in Leo P were unsuccessful. In 2025James Webb Space Telescope discovered rotational emission lines of H2 in themid-infrared part of the spectra leading to an estimate of the molecular hydrogen mass of the galaxy >104 solar masses.[6]
Leo P's stellar population consists of a strong concentration of massive, bright andblue stars in the centre of the galaxy, which may be B and A-typemain sequence stars. Some fainter and redder stars are also observed, presumablyred giants from an olderstellar population.[3] 10RR Lyrae stars have been detected in the galaxy, as well as oneH II region, which is ionised by LP26, anO-type star of 22 solar masses, the only one in Leo P.[7]
Leo P is one of the fewLocal Group galaxies which are currently forming stars. Its star formation rate is about4.3×10−5 M☉ every year,[2] or 1 solar mass every 20,400 years, and it is the Local Group's most metal-poor star-forming galaxy. Its star formation history shows mostly constant star formation throughout its lifetime, something which is also observed in larger irregular galaxies. Models also suggest that there was not much star formation post-reionisation, 12–8 billion years ago, and over the last 4 billion years, star formation has been happening at a constant rate.[2]
