47 Ursae Majoris (abbreviated 47 UMa), formally named Chalawan , is a yellow dwarf star approximately 46

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 from Earth 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 ...

of Ursa Major. , three extrasolar planets (designated

47 Ursae Majoris b 47 Ursae Majoris b (abbreviated 47 UMa b), formally named Taphao Thong , is a gas planet and an extrasolar planet approximately 46 light-years from Earth in the constellation of Ursa Major. The planet was discovered located in a long-period or ...

, c and d; the first two later named Taphao Thong and Taphao Kaew) are believed to orbit the star. The star is located fairly close to the Solar System: according to

astrometric Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. Histor ...

measurements made by the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

astrometry satellite, it exhibits a

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

of 71.11 milliarcseconds, corresponding to a distance of 45.913 light-years. With an apparent magnitude of +5.03, it is visible to the naked eye and its absolute magnitude of +4.29 implies a visual

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

around 60% greater than the Sun. A solar analog, with a spectral type of G1V, it has a similar mass to that of the Sun but is slightly hotter at around 5,882 K. and slightly more metal-rich with around 110% of the solar

abundance Abundance may refer to: In science and technology * Abundance (economics), the opposite of scarcities * Abundance (ecology), the relative representation of a species in a community * Abundance (programming language), a Forth-like computer prog ...

of iron. Like the Sun, 47 Ursae Majoris is on the

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 Her ...

, converting hydrogen to helium in its core by nuclear fusion. Based on its

chromospheric activity A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the S ...

, the star may be around six billion years old, though evolutionary models suggest an older age of around 8.7 billion years. Other studies have yielded estimates of 4.4 and 7 billion years for the star. The low level of magnetic activity makes it a Maunder Minimum candidate star.

Nomenclature

47 Ursae Majoris is the Flamsteed designation. On their discoveries the planets were successively designated 47 Ursae Majoris b, c and d. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning names were Chalawan for this star and Taphao Thong and Taphao Kaew for two of the planets (b and c, respectively). The winning names were submitted by the Thai Astronomical Society, Thailand. Chalawan ( th, ชาละวัน ) is a

myth Myth is a folklore genre consisting of Narrative, narratives that play a fundamental role in a society, such as foundational tales or Origin myth, origin myths. Since "myth" is widely used to imply that a story is not Objectivity (philosophy), ...

ological crocodile king from the Thai folktale

Krai Thong ''Krai Thong'' or ''Kraithong'' ( th, ไกรทอง, ) is a Thai folktale, originating from Phichit Province. It tells the story of Chalawan, a crocodile lord who abducts a daughter of a wealthy Phichit man, and Kraithong, a merchant from No ...

and Taphaothong and Taphaokaeo are two sisters associated with the tale. ('

Chalawan ''Krai Thong'' or ''Kraithong'' ( th, ไกรทอง, ) is a Thai folktale, originating from Phichit Province. It tells the story of Chalawan, a crocodile lord who abducts a daughter of a wealthy Phichit man, and Kraithong, a merchant from No ...

' is also the name given to an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of crocodylian. It contains a single species, ''Chalawan thailandicus''.) In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. In its first bulletin of July 2016, the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.

Planetary system

In 1996 an

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 ...

( 47 UMa b) was announced in orbit around 47 Ursae Majoris by

Geoffrey Marcy Geoffrey William Marcy (born September 29, 1954) is an American astronomer. He was an early influence in the field of exoplanet detection, discovery, and characterization. Marcy was a professor of astronomy at the University of California, Berk ...

and

R. Paul Butler Robert Paul Butler (born 1960) is an astronomer and staff scientist at the Carnegie Institution for Science in Washington, D.C., who searches for extrasolar planets. he and his team have discovered over half of the planets found orbiting nea ...

. The discovery was made by observing the

Doppler shift 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 ...

of the star's spectrum corresponding to changes in the star's

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 ...

as the planet's gravity pulled it around. The planet was the first long-period extrasolar planet discovered. Unlike the majority of known such planets, it has a low-eccentricity orbit. The planet is at least 2.53 times the mass of Jupiter and takes 1,078 days, or 2.95 years, to orbit its star. If it were to be located in the Solar System, it would lie between the orbits of Mars and Jupiter. 47UMaOrbits

In 2001, preliminary astrometric measurements made by the

probe suggested the orbit of 47 UMa b is

inclined Incline, inclined, inclining, or inclination may refer to: *Grade (slope), the tilt, steepness, or angle from horizontal of a topographic feature (hillside, meadow, etc.) or constructed element (road, railway, field, etc.) *Slope, the tilt, steepn ...

at an angle of 63.1° to the plane of the sky, implying the planet's true mass is around 2.9 times that of Jupiter. However, subsequent analysis suggested the Hipparcos measurements were not precise enough to accurately determine the orbits of substellar companions, and the inclination and true mass remain unknown. A second planet ( 47 UMa c) was announced in 2002 by Debra Fischer, Geoffrey Marcy and R. Paul Butler. The discovery was made using the same

method. According to Fischer et al., the planet takes around 2,391 days, or 6.55 years, to complete an orbit. This configuration is similar to the configuration of Jupiter 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 ...

in the Solar System, with the orbital ratio (close to 5:2) and mass ratio roughly similar. Subsequent measurements failed to confirm the existence of the second planet, and it was noted that the dataset used to determine its existence left the planet's parameters "almost unconstrained". Analysis of a longer dataset spanning over 6,900 days suggests that while a second planet in the system is likely, periods near 2,500 days have a high false-alarm probability, and the best fit model gives an orbital period of 7,586 days at a distance of 7.73 AU from the star. Nevertheless, the parameters of the second planet are still highly uncertain. On the other hand, the Catalog of Nearby Exoplanets gives a period of 2,190 days, which would put the planets close to a 2:1 ratio of orbital periods, though the reference for these parameters is uncertain: the original Fischer ''et al.'' paper is cited as a reference in spite of the fact that it gives different parameters, though this solution has been adopted by the '' Extrasolar Planets Encyclopaedia''. In 2010, the discovery of a third planet ( 47 UMa d) was made by using the

Bayesian Kepler Periodogram 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 th ...

. Using this model of this planetary system it was determined that it is 100,000 times more likely to have three planets than two planets. This discovery was announced by Debra Fischer and P. C. Gregory. This planet has an orbital period of 14,002 days, or 38.33 years, and a semi-major axis of 11.6 AU with a moderate eccentricity of 0.16. It would be the longest-period planet discovered by the radial velocity method, although longer-period planets had previously been discovered by

direct imaging Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of ...

and pulsar timing. Simulations suggest that the inner part of the habitable zone of 47 Ursae Majoris could host a terrestrial planet in a stable orbit, though the outer regions of the habitable zone would be disrupted by the gravitational influence of the planet 47 UMa b. However, the presence of a giant planet within 2.5 AU of the star may have disrupted planet formation in the inner system, and reduced the amount of water delivered to inner planets during

accretion Accretion may refer to: Science * Accretion (astrophysics), the formation of planets and other bodies by collection of material through gravity * Accretion (meteorology), the process by which water vapor in clouds forms water droplets around nucl ...

. This may mean any terrestrial planets orbiting in the habitable zone of 47 Ursae Majoris are likely to be small and dry. , there have been two METI messages sent to 47 Ursae Majoris. Both were transmitted from Eurasia's largest radar— Eupatoria Planetary Radar. The first message, the

Teen Age Message The Teen Age Message (TAM) was a series of interstellar radio transmissions sent from the Yevpatoria Planetary Radar to six solar-type stars during August–September 2001. The structure of the TAM was suggested by Alexander Zaitsev, Chief Scie ...

, was sent on September 3, 2001, and it will arrive at 47 Ursae Majoris in July 2047. The second message,

Cosmic Call 2 Cosmic commonly refers to: * The cosmos, a concept of the universe Cosmic may also refer to: Media * ''Cosmic'' (album), an album by Bazzi * Afro/Cosmic music * "Cosmic", a song by Kylie Minogue from the album '' X'' * CosM.i.C, a member of ...

, was sent on July 6, 2003, and it will arrive at 47 Ursae Majoris in May 2049. Because of its planetary system, 47 Ursae Majoris was listed as one of the top 100 target stars for NASA's former Terrestrial Planet Finder mission.

Notes

References

External links

* * {{Sky, 10, 59, 28.0, +, 40, 25, 49, 45.9 G-type main-sequence stars Ursae Majoris, 47 Maunder Minimum Planetary systems with three confirmed planets Ursa Major (constellation) BD+41 2147 Ursae Majoris, 47 0407 095128 053721 4277

Nomenclature

Planetary system

See also

Notes

References

External links