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Milky Way putting on weight as it hurtles toward oblivion
Source: Agencies |
January 7, 2009, Wednesday
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THE Milky Way could be crashing into the neighboring Andromeda galaxy sooner than predicted, scientists said yesterday.
But there's no need to panic - the event is still billions of years away.
For decades, astronomers thought, when it came to the major galaxies in Earth's cosmic neighborhood, that our Milky Way was a weak sister to the larger Andromeda. Not anymore.
It is considerably larger, bulkier and spinning faster than astronomers once thought, and Andromeda's equal.
Scientists mapped the Milky Way in a more detailed, three-dimensional way and found that it is 15 percent larger in breadth. More importantly, it is denser, with 50 percent more mass, which is like weight.
That difference means a lot, said study author Mark Reid of the Harvard-Smithsonian Center for Astrophysics.
"Previously we thought Andromeda was dominant, and that we were the little sister of Andromeda," Reid said. "But now it's more like we're fraternal twins."
Reid and his colleagues used a large system of 10 radio telescope antennas to measure the brightest newborn stars in the galaxy at different times in Earth's orbit around the sun.
They made a map of those stars, not just in the locations where they were first seen, but an additional dimension of time - something Reid said hadn't been done before.
With that, Reid was able to determine the speed at which the spiral-shaped Milky Way is spinning around its center.
That speed - about 914,000 kilometers per hour - is faster than the 791,800k/h that scientists had been using for decades.
That is about a 15-percent jump in spiral speed.
The old number was based on less accurate measurements and the current one was based on actual observations, Reid said.
Once the speed of the galaxy's spin was determined, complex formulas that end up cubing the speed determined the mass of all the dark matter in the Milky Way. And the dark matter - the stuff we cannot see - is by far the heaviest stuff in the universe. So that means the Milky Way is about one-and-a-half times the mass astronomers had previously calculated.
The study makes sense, but is not the final word on the size of the Milky Way, said Mark Morris, an astrophysicist at the University of California Los Angeles, who was not part of the study.
Being bigger means the gravity between the Milky Way and Andromeda is stronger.
So the long-forecast collision between the neighboring galaxies is likely to happen sooner and is less likely to be a glancing blow.
But don't worry. That is at least 2 to 3 billion years away, Reid said.
But there's no need to panic - the event is still billions of years away.
For decades, astronomers thought, when it came to the major galaxies in Earth's cosmic neighborhood, that our Milky Way was a weak sister to the larger Andromeda. Not anymore.
It is considerably larger, bulkier and spinning faster than astronomers once thought, and Andromeda's equal.
Scientists mapped the Milky Way in a more detailed, three-dimensional way and found that it is 15 percent larger in breadth. More importantly, it is denser, with 50 percent more mass, which is like weight.
That difference means a lot, said study author Mark Reid of the Harvard-Smithsonian Center for Astrophysics.
"Previously we thought Andromeda was dominant, and that we were the little sister of Andromeda," Reid said. "But now it's more like we're fraternal twins."
Reid and his colleagues used a large system of 10 radio telescope antennas to measure the brightest newborn stars in the galaxy at different times in Earth's orbit around the sun.
They made a map of those stars, not just in the locations where they were first seen, but an additional dimension of time - something Reid said hadn't been done before.
With that, Reid was able to determine the speed at which the spiral-shaped Milky Way is spinning around its center.
That speed - about 914,000 kilometers per hour - is faster than the 791,800k/h that scientists had been using for decades.
That is about a 15-percent jump in spiral speed.
The old number was based on less accurate measurements and the current one was based on actual observations, Reid said.
Once the speed of the galaxy's spin was determined, complex formulas that end up cubing the speed determined the mass of all the dark matter in the Milky Way. And the dark matter - the stuff we cannot see - is by far the heaviest stuff in the universe. So that means the Milky Way is about one-and-a-half times the mass astronomers had previously calculated.
The study makes sense, but is not the final word on the size of the Milky Way, said Mark Morris, an astrophysicist at the University of California Los Angeles, who was not part of the study.
Being bigger means the gravity between the Milky Way and Andromeda is stronger.
So the long-forecast collision between the neighboring galaxies is likely to happen sooner and is less likely to be a glancing blow.
But don't worry. That is at least 2 to 3 billion years away, Reid said.
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