|
|
The Question
(Submitted February 16, 2011)
When the Universe had cooled after the Big Bang to the point where the first
stars could form and given the sheer plentude of star forming materials that
would have been available then, how massive would the first stars have been
(compared to recently formed new massive stars) and what would the state
today of the black holes they formed when they nova'ed ~12-13 billion years
ago? How many black holes would have been formed in the first 100 million
years after the first star formation?
The Answer
Thanks for your question. One key aspect to the early Universe is that
the gas available to make stars did not have metals (which, to astronomers,
mean every element except hydrogen and helium), since metals came
later as a result of nuclear fusion in the stars themselves. This
effectively made cooling of gas slow and is thought to have lead to a
comparitively larger proportion of massive stars; some of which exceded
several hundred times the mass of the sun. By comparison, we are only
aware of stars reaching ~150 times the mass of the sun in the nearby
Universe. The question about how many black holes would have formed is of
significant debate and currently a topic of theoretical astronomy. It is
likely, however, that in the early Universe, when the size of the Universe
was small compared to today, many of these first black holes merged to give
rise to increasingly more massive black holes. These massive black holes
could then quickly "sink" to the centers of what would become
the galaxies. This is a leading theory for how the supermassive black
holes, commonly found at the centers of galaxies, formed over cosmic history.
(see, e.g.,
http://en.wikipedia.org/wiki/Supermassive_black_hole).
Bret & Antara
for Ask an Astrophysicist
|
