By Jonathan Amos

Science correspondent, BBC News

The galactic bubble known as RCW 120 lies some 4,300 light-years from Earth

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A colossal star many times the mass of our own Sun is seen growing in a bubble of excited gas just pictured by the Herschel space observatory. The image of the bubble, known as RCW 120, has been released a few days ahead of the European telescope's first birthday in orbit. Herschel's infrared detectors are tuned to see the cold materials that give birth to stars. Pictures like RCW 120 will help explain how really giant ones are made. The monster in this picture is seen as the small white blob on the bottom edge of the bubble. Please turn on JavaScript. Media requires JavaScript to play. The "baby" star is perhaps a few tens of thousands of years old and has yet to ignite the nuclear furnace that will form at its core. But it is some eight to 10 times the mass of our Sun and is surrounded by about 200 times as much material. If more of that gas and dust continues to fall in on the star, the object has the potential to become one of the Milky Way Galaxy's true giants, and it will go on to have a profound influence on its environment. "It's the massive stars that control the dynamical and chemical evolution of the galaxy," explained Herschel scientist Dr Annie Zavagno from the Laboratoire d'Astrophysique de Marseille. THE HERSCHEL SPACE TELESCOPE The telescope is sited over a million km from Earth Its instruments sense far-infrared and sub-millimetre radiation Its 3.5m diameter mirror is the largest ever flown in space Herschel can probe clouds of gas and dust to see stars being born It will investigate how galaxies have evolved through time The mission will end when its helium refrigerant boils off

Seeking the cold cosmos "It's the massive stars that create the heavy elements like iron and they are able to put them in the interstellar medium. And because they end their lives in supernova explosions, they also inject a lot of energy into the galaxy," she told BBC News. The baby owes its existence to another, unseen star, the radiation from which has sculpted the exquisite shape of the bubble. By pushing away this shroud of gas and dust, it has raised the density of matter in new locations, triggering a fresh round of starbirth. Present theories of star formation struggle to explain how objects larger than about 10 solar masses can exist. The fierce light they emit should blast away their birth clouds, limiting their growth. And yet, astronomers know of stars that are 120 times the mass of our Sun. The unique capabilities of Herschel - it works in the far-infrared and sub-millimetre range (55 to 672 microns) - mean it can see physical processes that are beyond the vision of other telescopes. Hubble, for example, which senses visible and near-infrared light, is blind to the details in this picture. Scientists hope Herschel's vision can give them the information they need to correct their models. The European Space Agency's billion-euro observatory was sent into orbit on an Ariane rocket on 14 May last year. It is positioned far from Earth to give it an unobstructed view of deep space. Jonathan.Amos-INTERNET@bbc.co.uk



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