An international team of researchers has debunked one of astronomy's long held beliefs about how stars are formed, using a set of galaxies found with CSIRO's Parkes radio telescope.
When a cloud of interstellar gas collapses to form stars, the stars range from massive to minute.
Since the 1950s astronomers have thought that in a family of new-born stars the ratio of massive stars to lighter ones was always pretty much the same — for instance, that for every star 20 times more massive than the Sun or larger, you'd get 500 stars the mass of the Sun or less.
"This was a really useful idea. Unfortunately it seems not to be true," said team research leader Dr Gerhardt Meurer of Johns Hopkins University in Baltimore.
The different numbers of stars of different masses at birth is called the 'initial mass function' (IMF).
Most of the light we see from galaxies comes from the highest mass stars, while the total mass in stars is dominated by the lower mass stars.
By measuring the amount of light from a population of stars, and making some corrections for the stars' ages, astronomers can use the IMF to estimate the total mass of that population of stars.
Results for different galaxies can be compared only if the IMF is the same everywhere, but Dr Meurer's team has shown that this ratio of high-mass to low-mass newborn stars differs between galaxies.
For instance, small 'dwarf' galaxies form many more low-mass stars than expected.
no time to comment.
No comments:
Post a Comment