APOD 1.2

2011 September 7
"SDSS J102915+172927: A Star That Should Not Exist"

The Sloan Sky survey catalogued a new star that has the lowest amount of metals yet. This would indicate that the star is one of the oldest ever studied since newer star tend to have more heavy metals such as lithium in them. What I found surprising was the "Population" numbering of stars that is used to differentiate between the ages of stars in the galaxy. In addition, I did not know that hydrogen is the most abundant element in the galaxy (about 90% of it) with helium is the second most abundant element. Besides random trivia, I learned that the population grading scale, that goes from I,II, III or earliest to latest stars, actually does not apply to SDSS because it is fifty times less lithium than what was thought to be needed for stars to form. This 13-billion old star, that exists in the constellation Leo and is 4/5ths the size of our own sun, is just one of a new group of stars that are smaller and less "metallic" than ever before. Maybe we can look forward with great anticipation for a new category of stars, Population IV!

http://apod.nasa.gov/apod/ap110907.html