HD 40307
Encyclopedia
HD 40307 is an orange (K-type) main sequence
star
located approximately 42 light-year
s away in the constellation
of Pictor
(the Easel
), taking its primary name from its Henry Draper Catalogue
designation. It is calculated to be slightly less massive than the Sun
. HD 40307 was observed during or before 1900 as part of the Cape Photographic Durchmusterung. In 2008, three extrasolar planet
s were discovered in orbit around it.
. This catalogue was based on spectral classifications made between 1911 and 1915 by Annie Jump Cannon
and her co-workers, and was published between 1918 and 1924. Unlike stars like Sirius
, Rigel
, and Betelguese, HD 40307 does not have a common, colloquial name.
. HD 40307's temperature has been observed to be slightly under 5000 K. This is relatively high for a K-type star and approaches the temperatures normally found in G-type stars such as the Sun.
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
and Saturn
.
of 7.17, is not visible to the naked eye. This star came within 1.97 pc of the Sun about 413 thousand years ago.
After spending five years observing the star, the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) announced that they had discovered three "Super-Earth
s" in orbit around HD 40307 in June 2008. All three planets were detected by the radial velocity
method, using the HARPS
spectrograph system. All three planets orbit extremely near the star, with the farthest member of the system located three times closer to HD 40307 than the planet Mercury
is to the Sun
.Mercury orbits at approx. 0.39 AU The planets are more massive than the Earth
, but may be less massive than Uranus
and Neptune
. Despite having masses less than 10 times that of Earth, dynamical analysis suggests that all three planets are determined to be gas giants like Uranus
and Neptune
. The radial velocity measurements also exhibit a linear trend, which may indicate the presence of an additional companion orbiting the star in a long-period orbit.
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...
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...
located approximately 42 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s 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 Pictor
Pictor
Pictor is a small and faint constellation in the southern sky , located between the brilliant star Canopus and the Large Magellanic Cloud. Its name is Latin for painter, but it is in fact an abbreviation of its original name Equuleus Pictoris, the 'painter's easel', and it is normally represented...
(the Easel
Easel
An easel is an upright support used for displaying and/or fixing something resting upon it.-Etymology:The word is an old Germanic synonym for donkey...
), taking its primary name from its Henry Draper Catalogue
Henry Draper Catalogue
The Henry Draper Catalogue is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension , published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the...
designation. It is calculated to be slightly less massive than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. HD 40307 was observed during or before 1900 as part of the Cape Photographic Durchmusterung. In 2008, three 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...
s were discovered in orbit around it.
History and nomenclature
The designation HD 40307 is from the Henry Draper CatalogueHenry Draper Catalogue
The Henry Draper Catalogue is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension , published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the...
. This catalogue was based on spectral classifications made between 1911 and 1915 by Annie Jump Cannon
Annie Jump Cannon
Annie Jump Cannon was an American astronomer whose cataloging work was instrumental in the development of contemporary stellar classification. With Edward C...
and her co-workers, and was published between 1918 and 1924. Unlike stars like Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...
, Rigel
Rigel
Rigel is the brightest star in the constellation Orion and the sixth brightest star in the sky, with visual magnitude 0.18...
, and Betelguese, HD 40307 does not have a common, colloquial name.
Characteristics
HD 40307, being a K-type star, emits orange-tinted light. Additionally, at approximately three-fourths the Sun's radius and mass, it is smaller and less massive than the SunSun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. HD 40307's temperature has been observed to be slightly under 5000 K. This is relatively high for a K-type star and approaches the temperatures normally found in G-type stars such as the Sun.
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
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,...
and Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
.
Distance and visibility
Despite its relative proximity to the Sun at 42 light-years, HD 40307, at an apparent magnitudeApparent 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...
of 7.17, is not visible to the naked eye. This star came within 1.97 pc of the Sun about 413 thousand years ago.
Planetary system
Super-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...
s" in orbit around HD 40307 in June 2008. All three planets were detected by the radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
method, using the HARPS
High Accuracy Radial Velocity Planet Searcher
The High Accuracy Radial velocity Planet Searcher is a high-precision echelle spectrograph installed in 2002 on ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003...
spectrograph system. All three planets orbit extremely near the star, with the farthest member of the system located three times closer to HD 40307 than the planet Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
is to the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
.Mercury orbits at approx. 0.39 AU The planets are more massive than the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, but may be less massive than Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...
and Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
. Despite having masses less than 10 times that of Earth, dynamical analysis suggests that all three planets are determined to be gas giants like Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...
and Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
. The radial velocity measurements also exhibit a linear trend, which may indicate the presence of an additional companion orbiting the star in a long-period orbit.
See also
- List of extrasolar planets
- Other stars with planets discovered in June 2008:
- HD 181433
- HD 47186HD 47186HD 47186 is a star located approximately 129 light-years away in the constellation of Canis Major. It is a G6V star with the characteristics very similar to the Sun, but it is 1.7 times more metal-rich. In 2008, two extrasolar planets were discovered orbiting the star.- Planetary system :Announced...
- MOA-2007-BLG-192LMOA-2007-BLG-192LMOA-2007-BLG-192L is a low-mass red dwarf star or brown dwarf, approximately 3,000 light-years away in the constellation of Sagittarius. It is estimated to have a mass approximately 6% of the Sun's...
External links
- A Trio of Super-Earths: A harvest of low-mass exoplanets discovered with HARPS, press release, European Southern ObservatoryEuropean Southern ObservatoryThe European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
, ESO 19/08, June 16, 2008.