Astrophysicist suggests planetary misalignment due to multiple star impact

Nov 15, 2012 by Bob Yirka report
Geometrical set-up of the problem. This figure depicts a schematic representation of the production of misaligned close-in planets through disk-driven migration in binary systems. Credit: (c) Nature, 491, 418–420 (15 November 2012) doi:10.1038/nature11560

(—Astrophysicist Konstantin Batygin has published a paper in the journal Nature arguing that the reason some planets lie in a tilt off the equatorial plane of their sun is because of the prior existence of another star that impacted their orbit. He suggests that systems that once hosted more than one star, but now do not, could also explain the existence of "Hot Jupiters" that have an orbit opposite of their host star.

"" are large, Jupiter-like planets that orbit very closely to their star. First discovered in 1995, it was assumed they formed at some distance from their and then migrated closer over time due to from gasses and dust around the star. Such a theory would suggest that the planet would naturally orbit in alignment with the star's equator. That theory was dashed however, when in 2008, researchers discovered that some Hot Jupiters did not have aligned orbits and that some in fact actually orbited in reverse of their sun. New theories have suggested this was due to the pull of other planets as the Hot Jupiter made its way closer to the star. Now, Batygin proposes another possibility – that the misalignment is due to the of another star that used to be part of the system, but has since departed.

Batygin notes that most solar systems today are binaries, and that some systems have more than two stars. To try to understand what sort of impact multiple stars might have on planets in those systems, he built and ran computer models. His simulations showed that disruptions to a planet's orbital path could very easily explain why some systems show a total misalignment of all its planets and that given the right circumstances, a complete flip-flop could occur, resulting in a planet orbiting in an opposite direction to their stars' spin. He adds that because the solar system in which Earth resides has a 7 degree tilt, it's very likely that one of the stars out there in the Milky Way today, once was part of our own solar system. He also suggests that it might be possible to strengthen his theory by comparing all of the known binary star formations with all known misaligned exoplanet systems.

Explore further: Is the universe finite or infinite?

More information: A primordial origin for misalignments between stellar spin axes and planetary orbits, Nature, 491, 418–420 (15 November 2012) doi:10.1038/nature11560

The existence of gaseous giant planets whose orbits lie close to their host stars ('hot Jupiters') can largely be accounted for by planetary migration associated with viscous evolution of proto-planetary nebulae. Recently, observations of the Rossiter–McLaughlin effect during planetary transits have revealed that a considerable fraction of hot Jupiters are on orbits that are misaligned with respect to the spin axes of their host stars3. This observation has cast doubt on the importance of disk-driven migration as a mechanism for producing hot Jupiters. Here I show that misaligned orbits can be a natural consequence of disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars. The gravitational torques arising from the dynamical evolution of idealized proto-planetary disks under perturbations from massive distant bodies act to misalign the orbital planes of the disks relative to the spin poles of their host stars. As a result, I suggest that in the absence of strong coupling between the angular momentum of the disk and that of the host star, or of sufficient dissipation that acts to realign the stellar spin axis and the planetary orbits, the fraction of planetary systems (including systems of 'hot Neptunes' and 'super-Earths') whose angular momentum vectors are misaligned with respect to their host stars will be commensurate with the rate of primordial stellar multiplicity.

add to favorites email to friend print save as pdf

Related Stories

Capturing planets

May 22, 2012

( -- The discovery of planets around other stars has led to the realization that alien solar systems often have bizarre features - at least they seem bizarre to us because they were so unexpected. ...

Two more kepler planets confirmed

Aug 08, 2011

Hot on the heels of confirming one Kepler planet, the Hobby-Eberly Telescope announces the confirmation of another planet. Another observatory, the Nordic Optical Telescope, confirms its first Kepler planet ...

'Hot Jupiter' planets unlikely to have moons

Aug 23, 2010

( -- Planets of the major type so far found outside our solar system are unlikely to have moons, according to new research reported in the August 20 issue of The Astrophysical Journal Letters.

New planet discovered in Trinary star system

Jul 14, 2011

Until recently, astronomers were highly skeptical of whether or not planets should be possible in multiple star systems. It was expected that the constantly varying gravitational force would eventually tug ...

Recommended for you

Is the universe finite or infinite?

Mar 27, 2015

Two possiblities exist: either the Universe is finite and has a size, or it's infinite and goes on forever. Both possibilities have mind-bending implications.

'Teapot' nova begins to wane

Mar 27, 2015

A star, or nova, has appeared in the constellation of Sagittarius and, even though it is now waning, it is still bright enough to be visible in the sky over Perth through binoculars or a telescope.

Dark matter is darker than once thought

Mar 27, 2015

This panel of images represents a study of 72 colliding galaxy clusters conducted by a team of astronomers using NASA's Chandra X-ray Observatory and Hubble Space Telescope. The research sets new limits on ...

Galaxy clusters collide—dark matter still a mystery

Mar 26, 2015

When galaxy clusters collide, their dark matters pass through each other, with very little interaction. Deepening the mystery, a study by scientists at EPFL and the University of Edinburgh challenges the ...

Using 19th century technology to time travel to the stars

Mar 26, 2015

In the late 19th century, astronomers developed the technique of capturing telescopic images of stars and galaxies on glass photographic plates. This allowed them to study the night sky in detail. Over 500,000 ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.