Astronomers discover 'tilted planets'

December 22, 2009
The COROT satellite

(PhysOrg.com) -- University of Exeter, UK, research has added to a growing evidence that several giant planets have orbits so tilted that their orbits can be perpendicular or even backwards relative to their parent star’s rotation.

Known as ‘extrasolar ’, because they are located outside our solar system, these planets orbit very closely to their star.

Planets are formed from a swirling disk of gas and dust that surrounds . Because the disk rotates in the same direction as the star, the planets spawned by the disk should revolve in the same direction. In an overcrowded , however, planets can push one body outward while flinging the other inward, elongating and tilting the inner planet’s orbit.

Published as a letter to the , the research involved examining the orbit of the first extrasolar planet discovered by the European satellite COROT. Known as COROT-Exo-1b, the planet can periodically be seen from Earth by telescope, as it passes across the face of its star. The research team observed the spectra of the star with the Keck telescope in Hawaii and discovered that its orbital axis was tilted at an angle of around 77 degrees.

The University of Exeter had already participated in the detection of two of these tilted planets in the past year, including the first know case, a planet known as “XO-3b”.

Since then astronomers worldwide have added their observations of tilted planets, making this one of the most talked-about phenomena of the year in astronomy. Currently between 25 and 50 percent of all whose angles of inclination have been measured have tilts exceeding 30 degrees. Of the planets in the solar system, Earth has the greatest orbital tilt relative to the sun’s axis of rotation, at an angle of 7.1 degrees.

Frédéric Pont of the University of Exeter's School of Engineering, Mathematics and Physical Sciences, said: “The presence of advanced life on Earth may be contingent on our planetary system having avoided the brunt of planet-planet scatter, keeping Earth on a circular orbit—neither too hot nor too cold for life as we know it. In this scenario, the may have been unusually lucky. Either it avoided catastrophic gravitational encounters between massive planets or it suffered such interactions so long ago that most of the planets had the chance to resettle into nearly circular orbits with little or no tilt.”

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4 comments

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TheWalrus
not rated yet Dec 22, 2009
Never mind. I was mistaking orbital tilt with axial tilt. Blush, blush.
TheWalrus
not rated yet Dec 22, 2009
More blushing, due to my original comment about Uranus's axial tilt not being posted for some strange reason.
jsa09
not rated yet Dec 22, 2009
I wonder what differences we would notice if planet earth had an orbit tilt of 90 degrees. A suns Polar orbit we could look down on the other planets in their orbit (given that ours is the only one we changed) except that it could be day time and therefore we may not see many at a time anyway.
A_Paradox
not rated yet Dec 28, 2009
TheWalrus,
no sweat buddy! The title of "Tilted Planets" did that to me too! Blame the journos! they don' write proper! [joking they have to make a buck too.] But the title should have been "Tilted Orbits".

I tend to think that if the planets of our Solar system all had very steeply tilted orbits relative to each other, it would lead to all sorts of traumatic instabilities. In other words we would not have evolved if, for example, a very elongated and tilted elliptical orbit for Earth meant that periodically the oceans froze solid, or that periodically the Earth's surface was blasted by great squadrons of thousands of comets drifting in from the Oort cloud.
Or some such.

It could be that we have come about only because Earth and the Solar system is a rather boring place by cosmological standards; like the "Hitch hikers guide" remarked: "Mostly harmless" :-)

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