APOD
Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
Sextans A: A Seemingly Square Galaxy
Explanation: 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.
| Date | November 3, 1998 |
|---|---|
| Credit | Credit: S. D. Van Dyk (IPAC /Caltech) et al., KPNO 2.1-m Telescope, NOAO |
| Authors & editors: | Robert Nemiroff (MTU) & Jerry Bonnell (UMCP) |
| A service of: |
ASD at NASA / GSFC, NASA Science Activation & Michigan Tech. U. |