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Massive black hole spits out fast star |
Chinese astronomers have uncovered the closest hypervelocity star to the Solar System
Lead researcher Zheng Zheng (inset) of the University of Utah, found the nearest hypervelocity stars discovered so far using the LAMOST device near Beijing
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| Chinese astronomers |
black hole at the centre of the Milky Way, at 2.3 million kilometres (1.4
million miles) per hour. This star is one of the speed demons of the
galaxy and gained its boost from the gravity of a black hole.
Although 42,400 light years from the Solar System, LAMOST-HVS1 (the
star’s name) is the closest so-called hypervelocity star to the Solar System,
of around 20 found so far. Once upon a time they each existed within a
binary star system that got too close to the supermassive black hole lurking
at the heart of the Milky Way. These binary stars are pulled away from
each other, with one being captured by the black hole and the other
gaining a gravitational energy boost that flings it away at high velocity.
The star was found by Chinese astronomers using the Large Sky
Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), which has given
its name to the star. The telescope is located at Xinglong Observing Station,
north-east of Beijing. With an array of 4,000 optical fibres the telescope is
able to capture the spectra of 4,000 stars simultaneously, which can
reveal information on a star’s size, temperature and velocity.
LAMOST-HVS1 is moving around three times faster than the other stars
around it. “If you’re looking at a herd of cows and one starts going 60 miles
[97 kilometres] per hour, that’s telling you something important,” says Ben
Bromley of the University of Utah. “You may not know at first what that
is. But for hypervelocity stars, one of the mysteries is where they come
from… the massive black hole in our galaxy is implicated.”
The location of LAMOST-HSV1 is among a group of other hypervelocity
stars 62,000 light years from the galaxy’s centre. According to Zheng
Zheng of the University of Utah, who led the study, the star “is the
nearest, second-brightest and one of the three most massive hypervelocity
stars discovered so far”. It has nine times the mass of our Sun and is
very bright, with a luminosity 3,400 times brighter than the Sun. It’s only
the sheer distance LAMOST-HSV1 lies from us that means it appears quite
faint to observers on Earth. Along with a group of other
astronomers around the world, Zheng will continue to study the speedy
LAMOST-HSV1 and other stars like it. What’s particularly interesting about
these stars is that they’re heading at high speed into the Milky Way’s
halo, which is filled with mysterious dark matter. How dark matter affects
the motion and velocity of these hypervelocity stars could one day
tell us something about what the mysterious substance is made of.
“ It has nine times the mass of our Sun and is very bright”
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