HIP 11915 b is an extrasolar planet orbiting the solar twin star HIP 11915, located about 190 light years (57 parsecs) away from Earth in the constellation Cetus. It is notable as the first exoplanet to be discovered with an orbit and mass extremely similar to that of Jupiter. The planet is essentially a "Jupiter analog", which suggests that the HIP 11915 system could be very similar to that of the Solar System. It orbits its star at a distance of approximately 4.8 AU. The exoplanet was found by using the radial velocity method, where periodic Doppler shifts of spectral lines of the host star suggest an orbiting object.
Characteristics[]
Mass, radius, and temperature[]
HIP 11915 b is a giant planet. It has a mass of 0.99 Jupiter mass (315 Earth mass) and a likely radius of around 1 Jupiter radius. Based on models, it is expected to have a temperature of around 118 K (-155 °C; -247 °F), almost the same as the planet Jupiter.
Host star[]
The host star, HIP 11915, is a G-type star that is the same mass of the Sun (a solar twin). It has a temperature of 5760 K, nearly the same as the Sun, which has a temperature of 5778 K. The star's age is estimated to be about 4.16 billion years old, about 540 million years younger than the Sun, which is 4.6 billion years old. The radius of the star has not been directly known, but given the same mass as the Sun, HIP 11915 likely has a radius of around 1.01 Solar radius, making it the same size as the Sun.
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 8.58. Therefore, HIP 11915 is too dim to be seen with the naked eye, but can be seen with good binoculars.
Orbit[]
HIP 11915 b orbits its host star with about 102% of the Sun's luminosity with an orbital period of 10 years and an orbital radius of about 4.8 AU. This is nearly the same as Jupiter, which has an orbital distance of about 5.2 AU. Its eccentricity is 0.1, slightly higher than Jupiter's. This would not have any effect on any residing planets near the star.
Significance in astronomy[]
The discovery of HIP 11915 b marked a significant breakthrough in the astronomy news. Because of its orbital distance and mass are just about the same as Jupiter, astronomers began to predict that star systems with Jupiter-like planets at the right orbital distance could have terrestrial planets in the inner portion, like the Solar System does.
While several Jovian-sized planets have been discovered, most have been found orbiting close to their stars. It is now hypothesized that Jupiter's movement in the Solar System may have cleared the way for the rocky inner planets, including Earth, to form. The similarity extends to the star that centers the system; like the Sun, HIP 11915 is a G-class star.