Scientists have long searched for evidence of the oldest stars in the universe. How do you know that you have such a star? By its spectrum. The spectrum of a star teaches you about the abundance of chemical elements in the atmosphere of the star. If it is one of the oldest stars in the universe, sometimes known as Population III stars, then it should have practically nothing but hydrogen and helium. Such stars have long evaded detection, but now, scientists of the European Southern Observatory (ESO) believe they may have found some. Learn more about the possible discovery of some of the oldest stars in our universe online now here.
Population III stars are the oldest stars in the universe. They were the first stars to form in the universe. In a paper to be published by the Royal Astronomical Society, available online now here, astronomer Jarrett Johnson addresses such questions as the link between dark matter haloes and the formation of Population III stars. It is estimated that there may be as many as thousands of these stars with a red shift between 2 and 7 (indicative of their distance). If so, Johnson expects that surveys to be done by the James Webb Space Telescope may be able to determine the number density of such Population III stars. If correct, the studies such as those proposed will be able to estimate how long the epoch of primordial star formation lasted.
I always enjoy seeing newly published research related to a topic that I’ve recently explored in my introductory astronomy course. In this case, the topic is Population III stars. As I was just telling my class yesterday, Population III stars are the oldest generation of stars. This would include the very first stars to form in our universe. Our own Sun is a Population I star, that is, it is a member of the youngest generation of stars. In a paper which appeared in the journal Science, available online now here, astronomers have developed computer models which predict that the “first stars to appear in the early universe” were very massive stars and likely formed in isolation.
In a pre-print released today, online now here, to appear in the journal Nature, astronomers provide a concise review of what is known today about the very first stars and galaxies that formed after the origin of the universe itself. In particular, the authors outline what we may be able to answer about these primordial stars and galaxies given the future ground-based and space-based instruments to be implemented. Astronomers conclude “that the first stars, so-called Population III (Pop III), were predominantly very massive.” The authors remind the readers that Population III stars are “those that initially contain no elements heavier than helium (’metals’ in the parlance of astronomers) other than the lithium produced in the Big Bang.”
When you talk to an astronomer about the evolution (actually a poor use of the term, better to say development) of stars, you may be told about how there are three major generations of stars, Population I, Population II and Population III stars. The oldest stars belong to the group called Population III stars. Our relatively young star, the Sun, belongs to the Population I star group. Now a group of American astronomers have proposed that there may have been stars even before Population III stars. These primordial stars are called dark stars because they were formed from dark matter. If correct, these astronomers point out that unlike our current stars, who produce energy by fusion of hydrogen into helium, these dark stars produce energy by annihilation of Weakly Interacting Massive Particles or WIMPs. The authors conclude that dark stars would result in the formation of black holes, something only the most massive “normal” stars can form. You can read more about dark stars here in a pre-print of a paper to be published in the Astrophysical Journal.
Astronomers hope to observe evidence of the first galaxies and stars born in this universe with the help of the James Webb Space Telescope (JWST). With an expected launch in 2013, JWST should allow astronomers to see galaxies with redshifts of about 10. That would mean that these galaxies formed about 13 billion years ago, not too long after the origin of this universe of ours. Also, the evidence for the first generation of stars, also known as Population III stars, should be in reach of JWST. Read more about how the JWST will assist astronomers to examine the very oldest galaxies and stars online now at http://xxx.lanl.gov/PS_cache/arxiv/pdf/0902/0902.3263v1.pdf
In a paper to appear later this year in the Astrophysical Journal, astronomers investigate the expected formation rate of what is called Population III stars. Our Sun is a Population I star. The previous generation of stars (about 5 billion years older) are called Population II stars. Population II stars do not have as many heavy chemical elements as do the Population I stars, as the heavier elements are formed in the supernovae explosions of the previous generation of stars. The oldest stars are called Population III stars, and these stars should have no heavy chemical elements in their spectra. Star formation rates are very important to astronomers’ calculations, and even show up in the famous Drake Equation used to estimate the number of civilizations in the Milky Way galaxy. Read more about the formation rate of Population III stars online at http://xxx.lanl.gov/PS_cache/arxiv/pdf/0901/0901.0735v1.pdf
Cosmic dust is an important field of study as it is the dust in nebulae which helps form things such as stars and planets. So where did all the dust out there come from? One NASA scientist joined a group of Japanese astronomers in modeling the formation and evolution of dust in primordial supernovae. They use observations of supernova remnants from the oldest known supernovae (called Population III supernovae) to test the results of their models. Learn more about the origins of cosmic dust online at http://xxx.lanl.gov/PS_cache/arxiv/pdf/0812/0812.1448v1.pdf And if you are curious about cosmic dust in general, you may want to take a look at a popular level presentation done by a colleague (Joe Weingartner) at http://physics.gmu.edu/~joe/NOVAC.pdf