Stars are the most basic entity within the universe, for they are present to varying degrees in galaxies, nebulae, open
and closed clusters as well as supernova remnants. They have graced the evening sky ever since man first started becoming
aware of his existence and have been intricately intertwined in culture, religion, superstition and many facets of human
Our galaxy is believed to contain 300 billion (3x108) stars whereas over 70 sextillion (7x1022) stars are believed to exist within the universe. The greatest accumulation of stars is in the form of galaxies where hundreds of billions of stars form these island universes. Less populous but still large accumulations of stars are observed in globular clusters where up to one million stars are strongly held together gravitationally (approximately 150 such clusters exist in our galaxy). Open clusters also involve a collection of stars (usually in the hundreds) which are weakly held gravitationally and are more frequent than globular clusters (at least 1500 open clusters exist in our galaxy).
Note: Star HE 1523-0901 lying in Libra is amongst a sample of bright metal-poor stars selected from the Hamburg-ESO Survey and whose age using various chronometers has been estimated to be 13.2 billion years old, thus making it one of the oldest known stars to date and which was created a mere 500 million years following the Big Bang. Using techniques similar to carbon-14 dating, the star's thorium and uranium abundance (amongst others) has helped establish the star's age as well as set a lower bound for the creation of the universe. This "galactic fossil" lies two degrees east of Zubeneschamali (â-Lib, mag 2.57) and reaches its greatest altitude at the southern meridian during summer and around midnight. For further details, see the article by Frebel et al (2007) here as well as the online article from Astronomy Magazine here.
Note: With a declination of -9.2°, HE 1523-0901 is a difficult imaging target for mid-northern latitudes and this task is further complicated by the geosynchronous satellite belt.
Please click on the image below to display in reverse colour (900x1200)
Proper Star Name:
RA / Dec:
15h 26m 01.2s /
-09° 11' 38"
B-V Color Index:
May 13, 2007
00:00 - 02:10 UT+3
AP 160 f/7.5 StarFire EDF
AP 1200GTO GEM
SBIG LRGB filters