Detail View: NASA Astronomy Picture of the Day Collection: Sextans A: A Seemingly Square Galaxy

Sextans A: A Seemingly Square Galaxy
What's bothering local galaxy Sextans A [ ]? A small dwarf irregular galaxy [ ] spanning 5 thousand light years across, Sextans A [ ] is located [ ] only 5 million light-years away. Named for its home constellation of Sextans [ ], the "diamond in the rough" structure relates to an ancient unknown event. 100 million years ago, something mysterious [ ] started a new wave of star formation in Sextans A's center [ ]. Massive short-lived stars exploded in supernovae [ ] that caused more star formation [ ] and yet more supernovae, ultimately resulting in an expanding shell [ ]. Today, young blue stars [ ] highlight areas and shell edges high in current star formation, a shell that from our perspective appears roughly square [ ]. In the above picture [ ], a bright orange star in our own Milky Way Galaxy [ ] appears superposed in the foreground.
Credit and Copyright: 
S. D. Van Dyk [ ] (IPAC [ ] /Caltech [ ]) et al., KPNO [ ] 2.1-m Telescope [ ], NOAO [ ]
Local Group
Goddard Space Flight Center (GSFC)
original url: