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

Title: 
Sextans A: A Seemingly Square Galaxy
Explanation: 
What's bothering local galaxy Sextans A [ http://spider.ipac.caltech.edu/staff/vandyk/sexa/ ]? A small dwarf irregular galaxy [ http://www.astro.uni-bonn.de/~dwarfs/ ] spanning 5 thousand light years across, Sextans A [ http://antwrp.gsfc.nasa.gov/apod/ap971114.html ] is located [ http://www.seds.org/messier/more/local.html ] only 5 million light-years away. Named for its home constellation of Sextans [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sextans.html ], the "diamond in the rough" structure relates to an ancient unknown event. 100 million years ago, something mysterious [ http://xxx.lanl.gov/abs/astro-ph/9808001 ] started a new wave of star formation in Sextans A's center [ http://www.journals.uchicago.edu/AJ/journal/issues/v115n1/970228/970228.text.html ]. Massive short-lived stars exploded in supernovae [ http://antwrp.gsfc.nasa.gov/apod/ap970225.html ] that caused more star formation [ http://antwrp.gsfc.nasa.gov/apod/ap980412.html ] and yet more supernovae, ultimately resulting in an expanding shell [ http://antwrp.gsfc.nasa.gov/apod/ap971002.html ]. Today, young blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap980803.html ] highlight areas and shell edges high in current star formation, a shell that from our perspective appears roughly square [ http://antwrp.gsfc.nasa.gov/apod/ap980427.html ]. In the above picture [ http://spider.ipac.caltech.edu/staff/vandyk/sexa/ ], a bright orange star in our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ] appears superposed in the foreground.
Credit and Copyright: 
S. D. Van Dyk [ mailto:vandyk@ipac.caltech.edu ] (IPAC [ http://www.ipac.caltech.edu/ ] /Caltech [ http://www.caltech.edu/ ]) et al., KPNO [ http://www.noao.edu/kpno/kpno.html ] 2.1-m Telescope [ http://www.noao.edu/kpno/40th/2.1m.html ], NOAO [ http://www.noao.edu/ ]
keyword: 
Local Group
facet_where: 
Goddard Space Flight Center (GSFC)
facet_what: 
Sextans
original url: 
http://antwrp.gsfc.nasa.gov/apod/ap981103.html
UID: 
SPD-APOD-ap981103