Stars rush about


Pick of the pics

Young stars rush about like naughty children

Flicking between images of a star cluster taken by the WFPC2 camera in the Hubble Space Telescope in 1997 and 2007 reveals individual stars moving, like those seen in the boxes. In two years of close examination, German astronomers have gauged the motions of more than 700 stars and found them to be faster than expected. Most of the cluster stars move by less than 1/10 of a pixel over the ten-year period, which is not discernible by eye. The object is the massive compact Young Cluster, NGC 3603, lying 20,000 light-years away in the Carina spiral arm of the Galaxy. Credit: NASA, ESA and Wolfgang Brandner (MPIA), Boyke Rochau (MPIA) and Andrea Stolte (University of Cologne)

Extracts from the Hubble press release

[If the flicking doesn’t work, go to this Hubble url to see it offered, on the right. NC]

With a mass of more than 10,000 suns packed into a volume with a diameter of a mere three light-years, the massive young star cluster in the nebula NGC 3603 is one of the most compact stellar clusters in the Milky Way and an ideal place to test theories for their formation.

A team of astronomers from the Max-Planck Institute for Astronomy in Heidelberg and the University of Cologne led by Wolfgang Brandner (MPIA) wanted to track the movement of the cluster’s many stars. Such a study could reveal whether the stars were in the process of drifting apart, or about to settle down.

The results for the motion of these cluster stars were surprising: this very massive star cluster has not yet settled down. Instead, the stars’ velocities were independent of their mass and thus still reflect conditions from the time the cluster was formed, approximately one million years ago.

In the long term such massive compact star clusters may lead to the development of the huge balls of stars known as globular clusters, whose tightly packed stars remain held together by gravity for billions of years.

Wolfgang Brandner (MPIA): This is the first time we have been able to measure precise stellar motions in such a compact young star cluster.

Andrea Stolte (Cologne): This is key information for astronomers trying to understand how such clusters are formed, and how they evolve.

Boyke Rochau (MPIA) Our measurements have a precision of 27 millionths of an arcsecond per year. This tiny angle corresponds to the apparent thickness of a human hair seen from a distance of 800 km.