Overview – Sagittarius Dwarf Irregular Galaxy
- Designations: Sagittarius Dwarf Irregular Galaxy, SagDIG, SGR Dwarf, ESO594-G004, PGC 63287, Kowal’s Object
- Object: Dwarf galaxy
- Constellation: Sagittarius
- Right ascension: 19h 29m 59.0s
- Declination: −17° 40′ 41″
- Apparent size: 2′.9 × 2′.1
- Apparent magnitude: 15.5
- Redshift: −79±1 km/s
- Distance: 3.4 million light years (1.04 Mpc)
The Sagittarius Dwarf Irregular Galaxy, also known as SagDIG, is a dwarf galaxy in the constellation of Sagittarius. It is located around 3.4 million light years away from Earth and has an apparent size of 2′.9 × 2′.1. Its right ascension is 19h 29m 59.0s and its declination is −17° 40′ 41″.
The small dwarf galaxy is part of the Local Group, but is thought to be the most remote from the Local Group’s barycenter. It is only slightly outside the zero-velocity surface of the Local Group.
The SagDIG should not be confused with the Sagittarius Dwarf Elliptical Galaxy, SagDEG. This is a seperate satellite galaxy of the Milky Way discovered decades later in the same constellation.
SagDIG has been through a prolonged period of star formation. This has resulted in it containing a rich intermediate-age population of stars. They are mostly young, with the average age between 4 and 8 billion years for the dominant population. There are twenty-seven candidate carbon stars that have been identified inside the galaxy. However, the majority of the population of the stars are metal-poor (at least [Fe/H] ≤ −1.3).
The Sagittarius Dwarf Irregular Galaxy was only found in the last few decades. It was discovered by Cesarsky et al. on a photographic plate taken for the ESO (B) Atlas on 13 June 1977 using the ESO 1 meter Schmidt telescope.
- Credit for the image: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)Acknowledgment: Y. Momany (University of Padua) – , , Public Domain, https://commons.wikimedia.org/w/index.php?curid=1206673