XO-2 is a

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

. It consists of two components: XO-2S (Also known as XO-2A) and XO-2N (Also known as XO-2B). This system is located approximately 500

light-years A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

away from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

in the Lynx constellation. Both of these stars are slightly cooler than the Sun and are nearly identical to each other. The system has a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of 11 and cannot be seen with the naked eye but is visible through a small

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

. These stars are also notable for their large

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

s. XO-2N and XO-2S have a separation of approximately AU.

Planetary systems

There are two known

exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

orbiting XO-2N. XO-2Nb (or rarely XO-2Bb), which is classified as a

hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere temp ...

, was discovered by the

XO Telescope The XO Telescope is an astronomical telescope located on the 3,054 m (10,000 foot) summit of Haleakala on Maui, Hawaii. It consists of two 200-millimeter telephoto camera lenses, and resembles binoculars in shape. It is used by the XO Project ...

using the

transit method Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty o ...

orbiting XO-2N (XO-2B) in 2007 and XO-2Nc was discovered in 2015 using the

radial velocity method Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in t ...

. Two planets were reported to orbit around XO-2S in 2014 using radial velocity method. One of them is Jupiter-mass and another has a mass comparable to Saturn. Both stars also show RV-trends, which may indicate the presence of additional long-periodic jovians or brown dwarfs around each of them.

References

External links

* NASA PlanetQuest
Planet race heats up: 1 month, 32 discoveries
* {{DEFAULTSORT:XO-2 (star) K-type main-sequence stars Lynx (constellation) Planetary transit variables Planetary systems with four confirmed planets 2 Binary stars

Planetary systems

See also

References

External links