CoRoT-7 (TYC 4799-1733-1) 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 ...

system. The primary, CoRoT-7A is a G-type main sequence

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

, slightly smaller, cooler, and younger than the Sun. It has an apparent magnitude of 11.67, fainter than

Proxima Centauri Proxima Centauri is a small, low-mass star located away from the Sun in the southern constellation of Centaurus. Its Latin name means the 'nearest tarof Centaurus'. It was discovered in 1915 by Robert Innes and is the nearest-kno ...

(mag. 11.05), the nearest star to the Sun. This star is approximately 520

light-year 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 ...

s away from the Solar System in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Monoceros (the Unicorn). The comoving companion CoRoT-7B was discovered in 2021. It is a red dwarf star.

Location and properties

The star is located in the LRa01 field of view of the CoRoT spacecraft. It is about 500 light years from Earth. According to the project website, this field is in the

Monoceros constellation Monoceros ( Greek: Μονόκερως, " unicorn") is a faint constellation on the celestial equator. Its definition is attributed to the 17th-century Dutch cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the no ...

. Published data lists the stellar properties as being a G9V yellow dwarf with a temperature of 5250 K, a radius of about 82% of the Sun and a mass of about 91% of the Sun. But other sources have listed it as a (K0V) orange dwarf. The

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

is 0.12 ± 0.06. The star is estimated to be about 150 parsecs away and with an age in the range 1.2 – 2.3 billion years, is younger than our own star which has an age of 4.6 billion years. The rotation period of the star, inferred by the lightcurve obtained by CoRoT, is around 23 days.

Planetary system

The primary star is orbited by the super-Earth

exoplanet 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 ...

CoRoT-7b CoRoT-7b (previously named CoRoT-Exo-7b) is an exoplanet orbiting the star CoRoT-7 in the constellation of Monoceros, from Earth. It was first detected photometrically by the French-led CoRoT mission and reported in February 2009. Until the anno ...

and CoRoT-7c, both discovered in 2009. A third planet CoRoT-7d, initially proposed in a 2010 study, was confirmed in 2022. The discovery of the inner planet was made using the transit method by the CoRoT program. CoRoT-7b is notable for its relatively small size, compared to other exoplanets known at the time. Because of their closeness to their star, these

s cannot be seen in a telescope; only their gravitational effect can be detected by the

Doppler effect The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who d ...

on the star's electromagnetic spectrum (radial velocity method), as well as transits of planet b. This star was reported to have stellar activity, making the confirmation process for CoRoT-7b more difficult. In fact, mass estimates are affected by large uncertainty due to stellar activity that perturbs the

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

measurements needed to "weigh" the planets. CoRoT-7d was first proposed by A. P. Hatzes et al in 2010 by 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 ...

. The existence of CoRoT-7d was disputed by a 2014 study, which concluded that the radial velocity signal was more likely to be an artifact of the stellar rotation. However, a 2022 study provided strong evidence for the existence of this planet, and it is now listed as a confirmed planet in the NASA Exoplanet Archive. CoRoT-7d's mass is 17.1 times that of Earth, but its volume and diameter are unknown. One year on CoRoT-7d would be equivalent to 8.966

day A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours, 1440 minutes, or 86,400 seconds. In everyday life, the word "day" often refers to a solar day, which is the length between two so ...

s on Earth.

References

External links

* {{DEFAULTSORT:CoRoT-7 G-type main-sequence stars M-type main-sequence stars Binary stars Planetary transit variables Planetary systems with three confirmed planets Monoceros (constellation)