HD 40307 is an orange ( K-type)

main-sequence In astronomy, 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 Hert ...

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 ...

located approximately 42

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 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 ...

Pictor Pictor is a constellation in the Southern Celestial Hemisphere, located between the star Canopus and the Large Magellanic Cloud. Its name is Latin for Painting, painter, and is an abbreviation of the older name Equuleus Pictoris (the "painter's ...

(the

Easel An easel is an upright support used for displaying and/or fixing something resting upon it, at an angle of about 20° to the vertical. In particular, easels are traditionally used by painters to support a painting while they work on it, normally ...

), taking its primary name from its Henry Draper Catalogue designation. It is calculated to be slightly less massive than the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. The star has six known

planets A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young ...

, three discovered in 2008 and three more in 2012. One of them,

HD 40307 g HD 40307 g is an exoplanet candidate suspected to be orbiting in the habitable zone of HD 40307. It is located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, usi ...

, is a potential

super-Earth A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to ...

in the

habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kas ...

, with an orbital period of about 200 days. This object might be capable of supporting liquid water on its surface, although much more information must be acquired before its habitability can be assessed. No stellar companions to HD 40307 were detected as in 2018.

History and nomenclature

HD 40307 was observed during or before 1900 as part of the

Cape Photographic Durchmusterung In astronomy, Durchmusterung or Bonner Durchmusterung (BD) is an astrometric star catalogue of the whole sky, compiled by the Bonn Observatory in Germany from 1859 to 1903. The name comes from ('run-through examination'), a German word used for ...

. The designation ''HD 40307'' is from the Henry Draper Catalogue, which is based on spectral classifications made between 1911 and 1915 by

Annie Jump Cannon Annie Jump Cannon (; December 11, 1863 – April 13, 1941) was an American astronomer whose cataloging work was instrumental in the development of contemporary stellar classification. With Edward C. Pickering, she is credited with the creation of ...

and her co-workers, and was published between 1918 and 1924.

Characteristics

As a K-type star, HD 40307 emits orange-tinted light. It has only about three-quarters of the

's radius and mass. Its temperature is measured at slightly under . The astronomers who discovered the planets orbiting HD 40307 suggested that the metallicities of stars determine whether or not the planetary bodies that orbit them will be terrestrial, like Earth, or gaseous, like

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

and

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

Distance and visibility

Despite its relative proximity to the Sun at 42 light-years, HD 40307 is not visible to the naked eye, given its

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 7.17. It came within 6.4 light-years of the Sun about 413,000 years ago.

Planetary system

A planetary system around HD 40307 contains four confirmed planets and two other possible planets, all within of the star. After spending five years observing the star, the European Organisation for Astronomical Research in the Southern Hemisphere (''ESO'') announced that they had discovered three

s in orbit around HD 40307 in June 2008. All three planets were detected by 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 ...

method, using the

HARPS The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ...

spectrograph system. In 2012, an independent analysis carried out by a team of astronomers led by

Mikko Tuomi Mikko Tuomi is a Finnish astronomer from the University of Hertfordshire, most known for his contributions to the discovery of a number of exoplanets, among them the Proxima Centauri b which orbits the closest star to the Sun. Mikko Tuomi was the ...

of the University of Hertfordshire confirmed the existence of these planets and found an additional three planets in the systems. The planet HD 40307 f on 51.6-day orbit was confirmed in 2015, with inconclusive evidence for the planets HD 40307 e and

. Five of the planets orbit very close to the star, with the farthest of them located twice as close to HD 40307 than is the planet

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

is to the

.Mercury orbits at approx. 0.39 AU The outermost planet orbits at a distance similar to the distance of

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...

to the

and is situated well in the system's

liquid water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a s ...

. The

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 detected by the radial veloc ...

es of the planets in the system ranges from three to ten times the

mass of the Earth An Earth mass (denoted as M_\mathrm or M_\oplus, where ⊕ is the standard astronomical symbol for Earth), is a unit of mass equal to the mass of the planet Earth. The current best estimate for the mass of Earth is , with a relative uncertainty ...

, placing them somewhere between

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 ...

and gas giants like

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus (mythology), Uranus (Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars (mythology), Mars), grandfather ...

and

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

. Dynamical analysis of the innermost planets suggests that planet b is unstable at its age unless it is an ice giant, having migrated from further away. That implies similar for the other planets, even further out. The most recent discovery also indicates via dynamical analysis that the true planetary masses can not be much higher than their minimum masses.

Notes

References

External links

A Trio of Super-Earths: A harvest of low-mass exoplanets discovered with HARPS
press release,

European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...

, ESO 19/08, June 16, 2008. {{DEFAULTSORT:HD 40307 040307 027887

2046 In contemporary history, the third millennium of the anno Domini or Common Era in the Gregorian calendar is the current millennium spanning the years 2001 to 3000 (21st century, 21st to 30th century, 30th centuries). Ongoing futures studies se ...

CD-60 01303 K-type main-sequence stars HD, 040307 Pictor (constellation) Planetary systems with four confirmed planets J05540421-6001245