The backward-spinning planets puzzle
Source: Agencies |
May 13, 2011, Friday
|
Print Edition
Print Edition
SOME planets are just flipping backward.
Of the more than 500 planets detected around stars besides our sun, the vast majority appear to spin the same way the star does, US scientists reported in the journal Nature.
But some of these extrasolar planets spin in the opposite direction of the stars they orbit, astronomers found.
These strange, backward-spinning planets are usually gassy giants called hot Jupiters, not rocky orbs like Earth.
Besides their backward twirling, which the astronomers call flipped orbits, these big planets huddle close to their stars, unlike Jupiter, which is about 778 million kilometers from the sun.
"That's really weird, and it's even weirder because the planet is so close to the star," Frederic Rasio of Northwestern University said in a statement.
"How can one be spinning one way and the other orbiting exactly the other way? It's crazy. It so obviously violates our most basic picture of planet and star formation."
Astronomers have long theorized that big gas planets form further away from their stars, while Earth-like rocks are born closer in.
But just because a Jupiter-like planet forms in the planetary boondocks doesn't mean it stays there, Rasio and his colleagues reported.
When planetary systems contain more than one planet, in addition to a star, each planet has its own gravitational force, causing the planets to interact and eventually pulling the gas giants close to the star or reversing its orbit, the scientists found.
This process is known as gravitational perturbation, an exchange of angular momentum.
Astronomers have been detecting extrasolar planets since 1995, but have seen only a handful to date.
Of the more than 500 planets detected around stars besides our sun, the vast majority appear to spin the same way the star does, US scientists reported in the journal Nature.
But some of these extrasolar planets spin in the opposite direction of the stars they orbit, astronomers found.
These strange, backward-spinning planets are usually gassy giants called hot Jupiters, not rocky orbs like Earth.
Besides their backward twirling, which the astronomers call flipped orbits, these big planets huddle close to their stars, unlike Jupiter, which is about 778 million kilometers from the sun.
"That's really weird, and it's even weirder because the planet is so close to the star," Frederic Rasio of Northwestern University said in a statement.
"How can one be spinning one way and the other orbiting exactly the other way? It's crazy. It so obviously violates our most basic picture of planet and star formation."
Astronomers have long theorized that big gas planets form further away from their stars, while Earth-like rocks are born closer in.
But just because a Jupiter-like planet forms in the planetary boondocks doesn't mean it stays there, Rasio and his colleagues reported.
When planetary systems contain more than one planet, in addition to a star, each planet has its own gravitational force, causing the planets to interact and eventually pulling the gas giants close to the star or reversing its orbit, the scientists found.
This process is known as gravitational perturbation, an exchange of angular momentum.
Astronomers have been detecting extrasolar planets since 1995, but have seen only a handful to date.
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