Eccentric Extrasolar Planet Discovered

Astronomers have just detected an extrasolar planet they described as eccentric, but not in a strange way.

Eccentric in this case means elliptical, referring to the comet-like orbit of the newly discovered planet. Astronomers from San Francisco State University, led by Dr. Stephen Kane, reported that they have spotted it outside our own solar system, at a distance of about 117 light-years from earth.

Catalogued as HD 20782, its discovery was officially published online on February 28 in The Astrophysical Journal.

The team detected it with reflected starlight from its atmosphere. They calculated the speed and trajectory of the orbit, thereby determining its eccentricity.

Kane explained in an article that eccentricity refers to the orbital path of a planet. The orbit could be a close to circular path or a very elliptical path with corresponding scale of between zero and one.

A perfectly circular orbit has an eccentricity of zero, while a very elliptical orbit has an eccentricity of one. Earth has an almost circular orbit with eccentricity of 0.017.

On the other hand, scientists have discovered that HD 2078 has an eccentricity of 0.96. By comparison, Mercury, the most elliptical orbit in our solar system, has its scale at 0.205.

The high eccentricity means that its elliptical path is almost flat and comparable to a comet's orbit. The planet takes 597 days to complete one revolution around its parent star.

Another intriguing thing about the planet is the reflected starlight, allowing scientists to indirectly study its atmospheric composition. An article has pointed out the possibility that the atmosphere was suddenly heated by the stellar wind of its parent star.

Researchers said that at the furthest point in its orbit, the HD 2087 sits very far from its star, about 2.5 times the distance between our Earth and the sun. At its closest, it comes even much closer than Mercury and the sun.

"It is around the mass of Jupiter, but it is swinging around its star like it is a comet," Kane said.