Spinning top: An artist's impression of the Milky Way showing the approximate position of our Solar System.
Credit: NASA/JPL-Caltech/R. Hurt
WASHINGTON DC: The Milky Way is spinning much faster and has 50 per cent more mass than previously believed, increasing the chance of a collision with another galaxy, say astronomers.
An international team of researchers have used ten telescopes spread out between Hawaii, the Caribbean and the northeastern United States to determine that the Milky Way is rotating at a speed of 161,000 km/h faster than previously thought.
Gravitational pull
That increase in speed boosts the Milky Way's mass by 50 per cent, said Mark Reid, of the Harvard-Smithsonian Centre for Astrophysics, in research presented at the American Astronomical Society meeting this week in Long Beach, California.
"No longer will we think of the Milky Way as the little sister of the Andromeda Galaxy," he said.
The larger mass, however, also means that the galaxy has a greater gravitational pull, which heightens the likelihood of collisions with the Andromeda galaxy or smaller nearby galaxies, Reid said.
The Earth's Solar System is located some 28,000 light years from the centre of the Milky Way. At that distance, the new measurements show that the galaxy is rotating at a speed of 965,600 km/h, compared to previous estimates of 804,672 km/h, the astronomers report.
The new observations from the network of radio telescopes is "producing highly-accurate direct measurements of distances and motions," said Karl Menten of the Max Planck Institute for Radio Astronomy in Germany, a member of the team.
Difficult to determine
"These measurements use the traditional surveyor's method of triangulation and do not depend on any assumptions based on other properties, such as brightness," Menten said. The direct measurements "are revising our understanding of the structure and motions of our Galaxy."
It is difficult to determine the structure of the Milky Way because the Earth is inside it.
"For other galaxies, we can simply look at them and see their structure, but we can't do this to get an overall image of the Milky Way," added Menten. "We have to deduce its structure by measuring and mapping."
Slow Her Down
"The Milky Way is spinning much faster and has 50 per cent more mass than previously believed, increasing the chance of a collision with another galaxy ... "
We've got to slow her down, then. We cannot have our galaxy recklessly flying through space in a collision course with everything in our way. It is inconsiderate to go bumping into someone else's galaxy.
Then we would die for sure :)
Then we would die for sure. Changing a well balanced system is never a good idea ;).
Measured where?
I wonder where the speed of 965,600 km/h was measured: surely the linear velocity at the Milky Way's border must be much higher than around the center. Is this figure measured from where we stand within the galaxy?
Re: Measured Where?
The Earth's Solar System is located some 28,000 light years from the centre of the Milky Way. At that distance, the new measurements show that the galaxy is rotating at a speed of 965,600 km/h (emphasis mine).
Good point though, the linear velocity does increase with distance from the center.
RE: Measured where
Indeed the linear velocity is substantially higher at the border. If you read the article, it states that the rotational speed measured is that of the Earth itself.
No border velocity is
No border velocity is actually lower than around the center. as you get closer everything speeds up because of super massive Black Hole. it is like an engine rotating spiral arms of the galaxy. And because inner speeds are higher then outer thats why arms form spirals. they get twisted.
Galactic rotational velocity is largely independent of radius
The gravity well of the solar system is not the same shape as the gravity well of the galaxy. Cosmologists discovered that the rotational speed of the Milky Way is fairly constant (approx 200km/s) from 3KLY out to 45KLY from the galactic center. This apparent violation of Kepler's law is one reason why cosmologists theorize that there is far more dark matter than ordinary matter in spiral galaxies. Since the outer regions are traveling almost the same speed as the inner regions it causes a lagging effect on the arms creating the spiral formation. If the outer regions were following Keplers law, the spiral would be wound so tightly that there would be no arms visible. Here is a reference site http://www.aoc.nrao.edu/~smyers/courses/astro12/L21.html
Measured where?
I wonder where the speed of 965,600 km/h was measured: surely the linear velocity at the Milky Way's border must be much higher than around the center. Is this figure measured from where we stand within the galaxy?
One of the wonderful mysteries of Galactic Physics
"surely the linear velocity at the Milky Way's border must be much higher than around the center. "
This is one of those hit your head and say "how could this be" things, but at the galactic level (Milky Way for example), galaxies rotate at the same speed at their outer edges as they do in their center. Totally defies newtonion physics (and totaly different from solar systems) and nobody knows for sure why this is (one of the reasons for all the talk of "dark matter").
Its a wonderful Universe out there and its shocking sometimes how little we understand it.
angular motion
so does this mean that the angular velocity decreases as 1/r? If so this would imply an infinite angular velocity at the centre(unphysical) and surely this would also result in quite notable movement of the stars in the sky, were as I cannot remember Orion's belt (the only easily discernable object in the light polluted skies of a modern city) moving from somewhere just west of south here in north east England in the early evening.