Astronomers discover ‘out of whack’ planetary system

May 25th, 2010 - 5:19 pm ICT by ANI  

Hubble Space Telescope Washington, May 25 (ANI): A team of astronomers has discovered a planetary system ‘out of whack,’ where the orbits of two planets are at a steep angle to each other.

The research tea, led by Barbara McArthur of The University of Texas at Austin McDonald Observatory, says that this surprising finding will affect theories of how multi-planet systems evolve and shows that some violent events can happen to disrupt planets’ orbits after a planetary system forms.

“The findings mean that future studies of exoplanetary systems will be more complicated. Astronomers can no longer assume all planets orbit their parent star in a single plane,” McArthur said.

McArthur and her team used data from Hubble Space Telescope (HST), thegiant Hobby-Eberly Telescope, and other ground-based telescopes combined with extensive modeling to unearth a landslide of information about the planetary system surrounding the nearby star UpsilonAndromedae.

McArthur reported these findings in a press conference at the 216th meeting of the American Astronomical Society in Miami, along with her collaborator Fritz Benedict, also of McDonald Observatory, and team member Rory Barnes of the University of Washington.

For just over a decade, astronomers have known that three Jupiter-type planets orbit the yellow-white dwarf star Upsilon Andromedae. Similar to our Sun, Upsilon Andromedae lies about 44 light-years away. It’s a bit younger, a bit more massive, and a bit brighter than the Sun.

Combining fundamentally different, yet complementary, types of data from HST and ground-based telescopes, McArthur’s team has determined the exact masses of two of the three known planets, Ups And c and d.

Much more startling, though, is their finding that not all planets orbit this star in the same plane. The orbits of planets c and d are inclined by 30 degrees with respect to each other.

This research marks the first time that the “mutual inclination” of two planets orbiting another star has been measured. And, the team has uncovered hints that a fourth planet, e, orbits the star much farther out.

“Most probably Upsilon Andromedae had the same formation process as our own solar system, although there could have been differences in the late formation that seeded this divergent evolution,” McArthur said.

“The premise of planetary evolution so far has been that planetary systems form in the disk and remain relatively co-planar, like our own system, but now we have measured a significant angle between these planets that indicates this isn’t always the case,” McArthur added.

The work also will be published in the June 1 edition of the Astrophysical Journal. (ANI)

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