XO-2b is an extrasolar planet

Extrasolar planet

An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...

 orbiting the star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 XO-2

XO-2 (star)

XO-2 is a cooler sun-like star located approximately 486 light-years away from Earth in the Lynx constellation. It has a magnitude of 11 and cannot be seen with the naked eye but is visible through a small telescope. This star is also notable for its large proper motion.This star shares magnitude...

 in the constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 Lynx

Lynx (constellation)

Lynx is a constellation in the northern sky, introduced in the 17th century by Johannes Hevelius. It is named after the lynx, a genus of cat. It is a very faint constellation; its brightest stars form a zigzag line.-History:...

. This planet was found by transit method in 2007 by Burke et al. This was the second such planet found by the XO telescope

XO Telescope

The XO Telescope is a telescope located on the 3,054 m summit of Haleakala on Maui, Hawaii, formed by a pair of 200 mm telephoto lenses. It is used to detect extrasolar planets using the transit method. It is similar to the TrES survey telescope...

.
Like most planets found by the transit method, it is a roughly Jupiter

Jupiter

Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

 sized planet that orbits very close to its host star; in this case, it has a surface temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 of about 1200 K

Kelvin

The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

, so it belongs to a group of exoplanets known as hot Jupiter

Hot Jupiter

Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...

s. The planet takes 2.6 days to orbit the star at the average distance of 0.0369 AU. The planet has mass of 57% of Jupiter and radius of 97% of Jupiter. The radius is relatively large for its mass, probably due to its intense heating from its nearby star that bloats the planet’s atmosphere

Atmosphere

An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

. The large radius for its mass gives a low density of 820 kg/m³.