When galaxies collide, fate of Earth dims, experts say
Milky Way and Andromeda bound to merge in 2 billion years
Global warming, the Iraq war, economic woes, fears of terrorism -- and now, just when it appeared things couldn't get any worse, astronomers predict the sun -- and Earth along with it -- will be hurled into deep space when our galaxy collides with a neighboring galaxy. Is Avocation Piece of At Be Dwelling A Or in of one Domicile Based action You? Because A work...What
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The galactic collision won't happen for a few billion years, but when it does, the entire solar system will be expelled from its current place in the bright galactic "suburbs" into the galactic boondocks, where there will be far fewer stars to guide sailors and to inspire the romantic.
Never again will the night skies be as pretty as they are now.
This less-than-sunny news comes from Harvard astronomer Thomas Cox and his colleague Avi Loeb, who used a supercomputer model to predict how the two galaxies will begin colliding in about 2 billion years.
"These types of merger events are very common," said Cox, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and a former San Francisco resident. "They are to a certain extent snapshots of what our future evolution holds."
Cox, 33, grew up in Santa Barbara, lived in Nob Hill from 1996-98 and received his astrophysics doctorate at UC Santa Cruz in 2004.
Loeb, an astronomy professor at Harvard who also works at the Harvard-Smithsonian Center, is a leading authority on the evolution of galaxies and the cosmos.
Our sun is one of a few hundred billion stars in the Milky Way, a pinwheel-like swirl of stars.
The Milky Way's biggest neighbor is another galaxy, Andromeda, which is more than 2 million light-years away. A light-year is the distance a beam of light travels in a year. A starship traveling at the speed of light would take more than 2 million years to reach Andromeda.
But no would-be Buck Rogers needs to fly to Andromeda, because it's flying toward us -- at approximately 60 miles per second, maybe faster. In other words, the Milky Way and Andromeda are doomed to collide, astronomers say.
For almost a century, astronomers have known that Andromeda is approaching the Milky Way. They concluded this after analyzing Andromeda's light spectrum as it shifted toward blue. In astronomy, if objects are becoming bluer, they are moving toward the observer, while objects that are becoming more intensely red are moving away. Astronomers continue to debate, however, over Andromeda's exact speed and direction -- whether it's pointed straight toward the Milky Way or at an angle.
Either way, astronomers agree that the two galaxies are so big that they won't miss each other. Right now, Andromeda is so far away that it appears as a small, faint glow in the night sky. But as it nears the Milky Way, its hundreds of billions of stars will stretch from horizon to horizon.
Using their computer model, Cox and Loeb forecast that after the collision about 2 billion years from now, the Milky Way and Andromeda galaxies will be pulled together by gravity and blend into a single, spherical super galaxy -- "Milkomeda," as Cox and Loeb call it.
In both galaxies, stars are so widely separated -- typically trillions of miles apart -- that it's highly unlikely any one star will hit another star during the merger.
The merger won't be entirely calm, however. During the collision, many stars will be hurled out of the galaxy, or at least into the galactic boondocks, like a fading Broadway celebrity who ends his career playing dinner theaters in Toledo.
According to Cox and Loeb's computer simulation, our sun probably will be one of those unlucky refugees hurled to the galactic edge. The sun is presently pretty far from the center of the Milky Way -- about 25,000 light-years. That means it's less tightly bound by gravity to the dense galactic center than closer-in stars.
Being gravitationally bound to the sun, Earth and the solar system's other planets will be pulled with it into the cosmic gloom.
It'll be much lonelier on the galactic periphery. The Earth and sun will be surrounded by only about one-tenth as many stars as they are now, according to Cox and Loeb's computer simulation.
"All the constellations we are used to will completely change," Loeb said.
A leading authority on galactic interactions called Cox and Loeb's findings credible.
"The authors are well-respected and the scenario they describe makes sense," said Professor Jean Brodie of UC Santa Cruz.
But Puragra "Raja" Guhathakurta, another astrophysicist at UC Santa Cruz, had a mixed reaction to the Cox-Loeb paper.
On the one hand, he said he agreed the two galaxies will collide and merge.
On the other hand, he said, there's debate among astronomers about the exact angle at which Andromeda is approaching the Milky Way.
"Exactly what the sun's location will be (after) all of this will depend a lot on the specific details of how (the two galaxies) approach each other," he said, "and at the moment we don't know the answer to this."