German project slims Milky Way
A team of scientists in Heidelberg have calculated that Earth's galaxy is much smaller than previously thoughtHeidelberg, Germany -- The Milky Way, the galaxy in which we live, has only half the mass it was previously thought to have, German scientists said Tuesday after calculating the orbit speeds of 2,400 stars.
The galaxy turns out to be a comparative lightweight in the universe, with a mass of only about 1,000 billion times the mass of our sun.
The findings were disclosed by the Max Planck Astronomy Institute in Heidelberg, and have been published on the internet.
The calculations were led by Xiang-Xiang Xue, who is a a PhD student in Heidelberg. She studied how much gravitational pull the galaxy and its dark matter must have to stop outer stars of the Milky Way whirling off into space.
"The galaxy turns out to have less mass than we expected," she said. "There's a lot less dark matter than supposed."
The same day, other astronomers in Germany who had devised a way to hook up two powerful telescopes in stereo said they had observed the details of a star outside our galaxy for the first time.
They trained the two telescopes on a red supergiant named WOH G64 in the Large Magellanic Cloud, a neighbouring galaxy. WOH is about 2,000 times larger than the sun and is 163,000 light years away.
Keiichi Ohnaka of the Max Planck Radio-Astronomy Institute in Bonn led the research.
He and his team worked with the European Southern Observatory (ESO) in Garching, a suburb of Munich, remotely using the ESO telescope complex, which is built on a desert mountain in Chile. They used two 8-metre-reflector scopes to create a virtual 60- metre telescope.
Normally a distant star only appears as a point of light. But the observations made visible how the ageing star was blowing much of its substance into space. It has lost 40 per cent of its original mass already, developing a shroud of dust around it. An explosion as a supernova is inevitable.
Xue's article meanwhile is set to be fully published this autumn in the Astrophysical Journal.