Astronomers have used telescopes on Earth and in space to nail the precise position of a mysterious, dark object at the outer edge of our Galaxy. The work could be an important step in understanding so-called dark matter — mysterious material that makes up about a quarter of our Universe.Most dark matter is believed to be in the form of subatomic particles that don't interact with regular atoms. But as much as 20% could also be in more traditional things that don't emit light, such as black holes and clouds of gas that never became stars. Such objects are thought to litter the galactic halo — the region beyond the visible disk of the Galaxy. They are known as Massive Compact Halo Objects, or MACHOs.MACHOs can be spotted ifthey pass in front of a distant star.
The object's gravitational field will bend the starlight like a lens, briefly making the star appear slightly brighter. But a single observation tells you only that the MACHO is between you and the star, not how far away it is. Two viewpoints allows distance to be calculated, similar to the way that binocular vision gives us depth perception.In the summer of 2005, Subo Dong, an astronomer at Ohio State University in Columbus and his colleagues watched from multiple ground-based telescopes as a distant MACHO caused a star in the Small Magellanic Cloud, a nearby galaxy, to briefly brighten. Half a day later, they watched the brightening again with the Spitzer Space Telescope, an infrared telescope orbiting 70 million kilometres from Earth. The delay corresponded to the time it took the MACHO to cross thespace between the lines of sight from Earth and the space telescope (see diagram). Based on this delay, the team calculated that the object lies some 16,000 light years away, putting it squarely in the Milky Way's halo. Dong suspects that the object is a pair of relatively small black holes orbiting each other. "I think it's great," says cosmologist and Nobel laureate John Mather of the Goddard Space Flight Center in Greenbelt, Maryland. Astrophysicists have long talked about making such measurements, but this is the first time they've done so successfully, Mather says.
View: Full Article | Source: Nature.com
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Posted on Friday, June 01 - 2007
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Tags Miscellaneous, Miscellaneous
Posted on Tuesday, August 24 - 2010
![]() Helium has a wide range of applications from use in hospitals to cleaning rockets but how much do we have left ?The world"s largest store of helium is located at a disused airfield in Texas however it is being sold off too cheaply with no way to replace it once its gone meaning that our supply could expire within just 25 years.
It is more commonly known as the gas that fills cheap party balloons and makes your voice squeak if you inhale it. Views : 10
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Tags Miscellaneous, Miscellaneous
Posted on Monday, August 23 - 2010
![]() A peculiar new fabric made in vats of tea is being used to create a range of new clothes and shoes.The innovative material is grown in a vat containing green tea, sugar and other nutrients. Scientists believe that the development of new fabrics is essential in relieving the pressure on the resources needed toproduce conventional materials. Views : 12
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Tags Nature, Miscellaneous
Posted on Thursday, August 19 - 2010
![]() In a remarkable story this week a surgeon removed most of a man"s skull and froze it in order to save his life.The Utah man had shattered his skull in multiple places after a longboarding accident, to reduce the swelling in his brain the neurosurgeon had to remove both sides of his skull and freezeit as a last resort. Views : 11
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Tags Super Science & Technology, Miscellaneous
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