Free Astronomy Magazine May-June 2016

SPACE CHRONICLES the cluster, all more than 100 times more massive as the Sun. However, the current record holder R136a1 does keep its place as the most mas- sive star known in the Universe, at over 250 solar masses. The detected stars are not only extremely massive, but also extremely bright. Together these nine stars outshine the Sun by a factor of 30 million. The scientists were also able to in- vestigate outflows from these behe- moths, which are most readily stud- ied in the ultraviolet. They eject up to an Earth mass of material per month at a speed approaching one percent of the speed of light, resulting in ex- treme weight loss throughout their brief lives. “The ability to distinguish ultraviolet light from such an exceptionally crowded region into its component parts, resolving the signatures of in- dividual stars, was only made possible with the instruments aboard Hub- ble,” explains Paul Crowther from the University of Sheffield, UK, and lead author of the study. “Together with my colleagues, I would like to acknowledge the invaluable work done by astronauts during Hubble’s last servicing mission: they restored by NASA A n international team of scien- tists using the NASA/ESA Hub- ble Space Telescope has com- bined images taken with the Wide Field Camera 3 (WFC3) with the un- precedented ultraviolet spatial res- olution of the Space Telescope Im- aging Spectrograph (STIS) to success- fully dissect the young star cluster R136 in the ultraviolet for the first time. R136 was originally listed in a catalogue of the brightest stars in the Magellanic Clouds compiled at the Radcliffe Observatory in South Africa. It was separated into three compo- nents a, b, c at the European South- ern Observatory, with R136a subse- quently resolved into a group of eight stars at ESO, and confirmed as a dense star cluster with the NASA/ ESA Hubble Space Telescope after the first servicing mission in 1993. R136 is only a few light-years across and is lo- cated in the Tarantula Nebula within the Large Magellanic Cloud, about 170,000 light-years away. The young cluster hosts many extremely massive, hot and luminous stars whose energy is mostly radiated in the ultraviolet. This is why the scientists probed the ultraviolet emission of the cluster. (Very massive stars are exclusive to the youngest star clusters because their lifetimes are only 2-3 million years. Only a handful of such stars are known in the entire Milky Way gal- axy.) As well as finding dozens of stars exceeding 50 solar masses, this new study was able to reveal a total number of nine very massive stars in Hubble unveils monster stars T he image shows the central re- gion of the Tarantula Nebula in the Large Magellanic Cloud. The young and dense star cluster R136 can be seen at the lower right of the image. This cluster contains hun- dreds of young blue stars, among them the most massive star detected in the Universe so far. [NASA, ESA, P. Crowther (University of Sheffield)]