Huge gas cloud will hit Milky Way
Pastor Dale Morgan
*Huge gas cloud will hit Milky Way*
By Paul Rincon
Science reporter, BBC News, Austin
The cosmic cloud is heading for us at more than 240km/s
A giant cloud of hydrogen gas is racing towards a collision with the
Milky Way, astronomers have announced.
Smith's Cloud, as it is known, may set off spectacular fireworks when it
smacks into our galaxy in 20-40 million years.
It contains enough hydrogen to make a million stars like the Sun, say
experts, and its leading edge is already hitting gas from our galaxy.
When it does hit, the cloud could indeed set off a new burst of star
formation in the Milky Way.
Details of the work, by a team at the US National Radio Astronomy
Observatory and the University of Wisconsin-Whitewater, were unveiled at
the 211th meeting of the American Astronomical Society in Austin, Texas.
Impressive sight
Smith's Cloud is named after the astronomer who discovered it in 1963.
But until now, astronomers had no idea whether it was leaving the Milky
Way or falling into it.
The new work by a team using the Green Bank telescope (GBT) in West
Virginia to observe the object shows, unmistakably, that the latter is true.
Smith's Cloud
Astronomers have taken detailed images of the cloud
Their new measurements also show that the cloud is 11,000 light-years
long and 2,500 light-years wide. The monster cosmic "fog bank" is
careering towards our galaxy at more than 240km/s (150 miles/s) and is
set to strike the Milky Way at an angle of 45 degrees.
Broadly speaking, the cloud is currently rotating with our galaxy, but
is also moving in towards it. Astronomers can see a wall of gas being
ploughed up as Smith's Cloud thuds into the outskirts of our galaxy's
atmosphere.
Lead author Dr Felix Lockman, from the NRAO, said the object, which lies
at a distance of 40,000 light-years from Earth, would make an impressive
sight if it could be seen with the naked eye.
"We don't know quite where it came from yet, as its orbit is a little
confused, but we can tell it is beginning to interact with the outskirts
of the Milky Way, that it is suffering drag and that bits of it are
falling off," Dr Lockman told the BBC News website.
"But at the same time, it is feeling the gravitational pull of the Milky
Way and is plunging in towards the disc."
By the time it merges with our galaxy, Smith's cloud will strike a
region some distance from the location of our Solar System, about 90
degrees ahead of us in the disc of the Milky Way.
Celestial New Year
Where it does collide, the cloud will generate shockwaves in the gas
already residing in the Milky Way.
"It will be just like letting a bomb go off," said Dr Lockman, "but you
also create a lot of new gas which may have different properties to the
existing gas.
The shockwaves will set off a tremendous burst of star formation. These
stars will be massive, rushing through their lives quickly and exploding
as supernova.
"Over a few million years, it'll look like a celestial New Year's
celebration, with huge firecrackers going off in that region of the
galaxy," said Dr Lockman.
Co-author Dr Robert Benjamin, from the University of
Wisconsin-Whitewater, told BBC News: "If the drag is sufficient, and the
cloud fragments, there could be less of an effect. But at the moment, it
looks like it is holding together quite tightly."
Astronomers have previously surmised that a region of bright stars
called Gould's Belt, which lies close to our own Sun, could have been
created in just this way.
"This is the first time we're actually seeing it happen," said Dr Lockman.
"The Milky Way is still under bombardment ż there are still fragments of
it coming in and arriving on the scene. When this happens, it can bring
fresh gas and trigger new star formation. And it's interesting to
speculate whether this [once] happened near the Sun."
The gas cloud was discovered in 1963 by the young American astronomer
Gail Smith working at Leiden University in the Netherlands. She
subsequently left science but still lives in the Netherlands.