Sextans A

Sextans A (also known as UGCA 205) is a tiny dwarf irregular galaxy. It spans about 5000 light-years across, and is located at 4.3 million light-years away, in the outskirts of the Local Group of galaxies, which includes the Milky Way galaxy, and to which Sextans A may or may not belong.

Sextans A
Irregular galaxy Sextans A. The bright Milky Way foreground stars appear yellowish in this view. Beyond them lie the stars of Sextans A with young blue star clusters clearly visible.
Observation data (J2000 epoch)
Constellation	Sextans
Right ascension	10h 11m 00.8s[1]
Declination	−04° 41′ 34″[1]
Redshift	324 ± 2 km/s[1]
Distance	4.31 ± 0.13 Mly (1.32 ± 0.04 Mpc)[2][3][4]
Apparent magnitude (V)	11.9[1]
Characteristics
Type	IBm[1]
Apparent size (V)	5′.9 × 4′.9[1]
Notable features	Square in shape
Other designations
UGCA 205,[1] DDO 75,[1] PGC 29653[1]

Sextans A has a peculiar square shape. Massive short-lived stars exploded in supernovae that caused more star formation, triggering yet more supernovae, ultimately resulting in an expanding shell. Young blue stars now highlight areas and shell edges high in current star formation, which from the perspective of observers on Earth appears roughly square.[5] The 10.4m telescope Gran Telescopio Canarias recently observed the OB-type stars that power the giant HII regions.[6]