HD 7924 b
Encyclopedia
HD 7924 b is an extrasolar planet
located approximately 54 light years away in the constellation
of Cassiopeia
, orbiting the 7th magnitude
K-type main sequence
(slightly metal poor) star
HD 7924
. It was published on January 28, 2009 and is the second planet discovered in the constellation Cassiopeia. (The first planet discovered in this constellation is HD 17156 b
, which was published on April 14, 2007).
exoplanet with a minimum mass
9.2 times that of Earth and takes only about 129.5 hours to orbit the star, at an average distance of 8500000 km (5,281,668.3 mi). When HD 7924 b was discovered in 2009, it was one of only eight planets known with a minimum mass less than 10 Earths. Also a super-Earth discovery makes 2009 the fifth year in a row since 2005 to have super-Earth planets discovered.
. Since the true mass
of this planet is not known, it might be gaseous if the true mass is considerably more than minimum mass. If the true mass is near the minimum mass of 9.2 ME
, then this planet could be rocky.
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...
located approximately 54 light years away 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....
of Cassiopeia
Cassiopeia (constellation)
Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty. Cassiopea was one of the 48 constellations listed by the 2nd century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today...
, orbiting the 7th magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
K-type main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
(slightly metal poor) 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...
HD 7924
HD 7924
HD 7924 is a 7th magnitude K-type main sequence star located approximately 55 light years away in the constellation Cassiopeia. This star is smaller, cooler, dimmer, and less massive than our Sun. Also its metal content is about seven-tenths as much as the Sun. In 2009, a super-Earth exoplanet was...
. It was published on January 28, 2009 and is the second planet discovered in the constellation Cassiopeia. (The first planet discovered in this constellation is HD 17156 b
HD 17156 b
HD 17156 b is an extrasolar planet approximately 255 light-years away in the constellation of Cassiopeia. The planet was discovered orbiting the yellow subgiant star HD 17156 in April 2007. The planet is classified as a relatively cool hot Jupiter planet slightly smaller than Jupiter but slightly...
, which was published on April 14, 2007).
Super-Earth
HD 7924 b is a super-EarthSuper-Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's gas giants. The term super-Earth refers only to the mass of the planet, and does not imply anything about the surface conditions or habitability...
exoplanet with a minimum mass
Minimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...
9.2 times that of Earth and takes only about 129.5 hours to orbit the star, at an average distance of 8500000 km (5,281,668.3 mi). When HD 7924 b was discovered in 2009, it was one of only eight planets known with a minimum mass less than 10 Earths. Also a super-Earth discovery makes 2009 the fifth year in a row since 2005 to have super-Earth planets discovered.
Characteristics
While the radius of HD 7924 b is unknown, depending on its composition, it will be between 1.4–6 times the diameter of the Earth. It is unknown whether this planet is rocky or gaseousGas giant
A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...
. Since the true mass
True mass
The term true mass is synonymous with the term mass, but is used in astronomy to differentiate the measured mass of a planet from the lower limit of mass usually obtained from radial velocity techniques...
of this planet is not known, it might be gaseous if the true mass is considerably more than minimum mass. If the true mass is near the minimum mass of 9.2 ME
Earth mass
Earth mass is the unit of mass equal to that of the Earth. 1 M⊕ = 5.9722 × 1024 kg. Earth mass is often used to describe masses of rocky terrestrial planets....
, then this planet could be rocky.