by dougettinger » Fri Apr 09, 2010 3:34 pm
Chris Peterson wrote:dougettinger wrote:Then, I presume the stars in galaxial globular star clusters are consistently very old stars with very little higher metals. I believe astronomers call them Population I stars. I would also presume that these stars are all mid-size or smaller stars that would have long lives that compare with the age of the universe less 1 or 2 billion years. Are these presumptions proven by observational data?
Population I stars are high metal content, like the Sun. Globular clusters are made up of low metal, Population II stars, like those found in the galactic halo and bulge. The stars all appear to have formed at the same time, but they don't all have the same mass, so you find a range of luminosities. The stars in globulars are very old, as you suggest. Most seem to be about a billion years younger than the Universe- the same as galaxies. This is all well supported by observation. There are a small number of globulars that have different characteristics, such as split star populations. These aren't well understood, but might be the product of later evolution due to collisions or tidal effects.
Chris, thanks for answering my question and correcting me about Population I and Population II stars. Is it correct to assume then that most subsequent generation stars, young massive short-lived blue stars, and Population I stars with high metal content are mostly made in spiral and barred galaxies and irregular galaxies like the LMC? Older, possibly original stars, are mostly found in elliptical galaxies and the bulges/globular clusters of spiral galaxies.
[quote="Chris Peterson"][quote="dougettinger"]Then, I presume the stars in galaxial globular star clusters are consistently very old stars with very little higher metals. I believe astronomers call them Population I stars. I would also presume that these stars are all mid-size or smaller stars that would have long lives that compare with the age of the universe less 1 or 2 billion years. Are these presumptions proven by observational data?[/quote]
Population I stars are high metal content, like the Sun. Globular clusters are made up of low metal, Population II stars, like those found in the galactic halo and bulge. The stars all appear to have formed at the same time, but they don't all have the same mass, so you find a range of luminosities. The stars in globulars are very old, as you suggest. Most seem to be about a billion years younger than the Universe- the same as galaxies. This is all well supported by observation. There are a small number of globulars that have different characteristics, such as split star populations. These aren't well understood, but might be the product of later evolution due to collisions or tidal effects.[/quote]
Chris, thanks for answering my question and correcting me about Population I and Population II stars. Is it correct to assume then that most subsequent generation stars, young massive short-lived blue stars, and Population I stars with high metal content are mostly made in spiral and barred galaxies and irregular galaxies like the LMC? Older, possibly original stars, are mostly found in elliptical galaxies and the bulges/globular clusters of spiral galaxies.