The star-forming region NGC 3603 in 2007 - seen in the Hubble Space Telescope image.
Credit: Hubble Space Telescope
SYDNEY: A team of astronomers in Germany measured tiny motions of young stars, and were surprised to find that it is independent of mass.
Astronomers compared two observations made 10 years apart of the star-forming region NGC 3603 using the Hubble Space Telescope.
It took the team from the Max-Planck Institute for Astronomy in Heidelberg and the University of Cologne two years to analyse and to estimate the motions of the stars from images taken in July 1997 and September 2007.
Lower mass stars
In the end they measured the precise speeds of more than 800 stars, and published the result in The Astrophysical Journal Letters.
The results showed the stars moving in ways that are at odds with the current understanding of how such clusters evolve.
"In a cluster one would expect that stars with lower mass have, on average, higher velocities. This suggests that the cluster has not yet achieved such an equilibrium but rather shows signs of the formation process," said Boyke Rochau, the paper's lead author.
Birthsites of the stars
Stellar clusters are the birthsites of most stars and the only place where the massive stars are forged - those with a mass in excess of 10 suns or more.
The cluster, formally known as the NGC 3603 Young Cluster, is about 20,000 light-years from the Sun, which made measurements difficult. However, it was important to get an insight into the cluster's fate:
"This particular cluster is even exceptional among the population of clusters in the Milky Way since it is one of the most massive young clusters that we can find in the galaxy," said Rochau.
Not dependent on mass
The study is an important development, according to astronomer Dougal Mackey, who researches star clusters at the Australian National University.
"We don't have that much knowledge of younger star clusters so this opens the door for us to learn more about the condition of how the clusters evolve," he said.
Mackey finds it surprising that the speed of the stars not necessarily is depended on the mass of the stars.
"We used to assume that massive stars slowed down quickly but this research show us that it is not a good assumption to make with very young clusters," he said.
