First Picture of Likely Planet around Sun-like Star

[LunaSea]

http://www.gemini.edu/sunstarplanet



September 15, 2008

Astronomers have unveiled what is likely the first picture of a planet around a normal star similar to the Sun.

Three University of Toronto scientists used the Gemini North telescope on Mauna Kea in Hawai‘i to take images of the young star 1RXS J160929.1-210524 (which lies about 500 light-years from Earth) and a candidate companion of that star. They also obtained spectra to confirm the nature of the companion, which has a mass about eight times that of Jupiter, and lies roughly 330 times the Earth-Sun distance away from its star. (For comparison, the most distant planet in our solar system, Neptune, orbits the Sun at only about 30 times the Earth-Sun distance.) The parent star is similar in mass to the Sun, but is much younger.

“This is the first time we have directly seen a planetary mass object in a likely orbit around a star like our Sun,” said David Lafrenière, lead author of a paper submitted to the Astrophysical Journal Letters and also posted online. “If we confirm that this object is indeed gravitationally tied to the star, it will be a major step forward.”

[bananas]

1. Is it a planet, or a binary star?

[pokerfan]

2. Not with a mass of only eight Jupiters

The spectral analysis would also look much different.

[Odin2005]

3. If it is above 17 Jupiter masses it is a Brown Dwarf star, below 17 and it's a Gas Giant planet.

IIRC 17 Jupiter masses is the minimum amount of mass needed for an object to start fusing deuterium ("heavy hydrogen"), but deuterium is not very abundant so the fusion only lasts for a short time and "true" proton-proton fusion never starts. Objects that are massive enough for deuterium fusion but not proton-proton fusion are called Brown Dwarfs.

Brown Dwarfs and Gas Giants are also thought to tend to have different origins. It is thought that most brown dwarfs are formed like other starts, but just happen to not get enough mass for proton-proton fusion. Gas Giants start out like most planets do, from the disk of debris surround a young star, in the outer solar system you have lots of ice that allow proto-planets of 10 earth-masses to form, when that point is reached these giant ice-balls start sucking up the surrounding gas and become Gas Giants