Comets are small icy bodies that light up when they near the sun as solar ice they were a bright tail to create to evaporate.
new computer simulations of billions of comets crisscrossing the solar system indicate that most of them originate outside our local area, but it grabbed and pulled by the gravity of our sun later.
Scenario unlike the old model for the evolution of comets, which holds that most of our local comets come from the same area where the sun and planets formed. This region, known as the Oort cloud surrounding the solar system and extends far beyond Pluto.
According to researchers it Levison, an astronomer at the Southwest Research Institute in Boulder, Colorado, but "the standard model can not generate near the amount of comets we see."
"This model says that comets are the dregs of planet formation of our solar system and our planet's gravity boot them to a very great distance, fill the cloud," said Levison. Such a process tends to occur around other stars as well, with each giving rise to their own cloud of comet debris.
But the star may not have been at their initial cloud.
Like the other stars, the sun gave birth in the open star clusters are destroyed from time to time. The cluster usually contains between ten and a thousand stars jammed into a small space, an average radius is not much different from the Oort cloud today. Near the star in the group may have allowed the star to "steal" young comets from each other.
And the stars would not have been the greatest to the most successful thief. As the comet moves far enough away from the star and close enough to the sun, for example, can trap the sun's gravity, even if the parent star is much larger.
If it does not add
The distance of the Oort cloud from the ground makes it difficult to see - let alone pin down the exact number of comets contain. The number of comets that are derived from their observations of the comet, which lights when they passed near the sun.
But based on this data, Levison and his team said there was about 400000000000 comets floating just outside Pluto. For comparison, the conventional model predicts only 6 billion.
"This is ... a big difference," says Levison. "Too big to be explained by errors in the budget is not possible for us to much, so there must be something wrong with the model itself .."
Long period comet orbits that these findings appear to support. they are highly elliptical orbits take them far into the depths of space.
"So they could not have been born in orbit around the sun," says Levison. "They have now formed to other stars, and then here was hijacked."
Comets are generally considered a very good picture of the early solar system, because they spend most of their lives encased in ice. And if some comets come from outside our solar system, they can tell us about their parent stars, too.
"We have the orbits of comets can be studied and their chemical put in the context of and around their stars formed," says Levison. "It's exciting to think we have some" goods "we in the distant star us. Family."