BD+14 4559 b, named Pirx, is an

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

orbiting the

K-type main sequence star A K-type main-sequence star, also referred to as a K-type dwarf, or orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("r ...

BD+14 4559 BD, Bd or bd may refer to: In arts and entertainment * B. D. (Doonesbury), a major character in the ''Doonesbury'' comic strip * ''Bande dessinée'' (or "bédé"), a French term for comics * Bass drum, in sheet music notation * Brahe Djäknar ...

about 161

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s (49

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s, or nearly km) from Earth in the constellation

Pegasus Pegasus (; ) is a winged horse in Greek mythology, usually depicted as a white stallion. He was sired by Poseidon, in his role as horse-god, and foaled by the Gorgon Medusa. Pegasus was the brother of Chrysaor, both born from Medusa's blood w ...

. It orbits its star within the

habitable zone In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...

at a distance of 0.777 AU, close to that of

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

, but its star is less energetic, thus its habitable zone is closer to it than Earth. The exoplanet was found by using 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 th ...

, from radial-velocity measurements via observation of

Doppler shift The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described t ...

s in the

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

of the

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

's parent star. The planet was named during the

NameExoWorlds NameExoWorlds (also known as IAU NameExoWorlds) were various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, notably exoplanets. The accepted names would later be cons ...

campaign by

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

. Pilot Pirx is a fictional character from stories by Polish

science-fiction Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, sp ...

writer

Stanisław Lem Stanisław Herman Lem (; 12 September 1921 – 27 March 2006) was a Polish writer. He was the author of many novels, short stories, and essays on various subjects, including philosophy, futurology, and literary criticism. Many of his science fi ...

Characteristics

Mass, radius and temperature

BD+14 4559 b is a

gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...

, an exoplanet that has a radius and mass around that of the gas giants

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 Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

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 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

. It has a temperature of . It has an estimated mass of around 1.2 and a potential radius of around 1.05 based on its mass.

Host star

The planet orbits a ( K-type)

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

named

. The star has a mass of 0.86 and a radius of around 0.95 . It has a surface temperature of 5008 K and is likely about 3 billion years old based on its evolution and mass. In comparison, the Sun is about 4.6 billion years old and has a surface temperature of 5778 K. The star's

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

, or how bright it appears from Earth's perspective, is 9.63. Therefore, BD+14 4559 is too dim to be seen with the naked eye, but can be viewed using good binoculars.

Orbit

BD+14 4559 b orbits its star every 268 days at a distance of 0.77 AU (close to

's orbital distance from the Sun, which is 0.72 AU). It has a mildly eccentric orbit, with an eccentricity of 0.29.

Discovery

The search for BD+14 4559 b started when its host star was chosen an ideal target for a planet search using the

(in which the gravitational pull of a planet on its star is measured by observing the resulting

), as stellar activity would not overly mask or mimic

Doppler spectroscopy 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 ...

measurements. It was also confirmed that BD+14 4559 is neither a binary star nor a quickly rotating star, common

false positive A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resu ...

s when searching for transiting planets. Analysis of the resulting data found that the radial velocity variations most likely indicated the existence of a planet. The net result was an estimate of a 1.47 planetary companion orbiting the star at a distance of 0.77 AU with an eccentricity of 0.29. Radial velocity measurements of BD+14 4559 were measured at 43 epochs over the period of roughly 1,265 days (around 4 years) using the

Hobby–Eberly Telescope The Hobby–Eberly Telescope (HET) is a telescope located at the McDonald Observatory in Davis Mountains, Texas. The Hobby–Eberly Telescope is one of the largest optical telescopes in the world. It combines a number of features that differe ...

. Measurements determined that a signal-to-noise ratio per resolution element was around 150–260 at 594 nm in 10 to 25 minutes of integration. The estimated mean RV uncertainty for the parent star was estimated at 8 m s⁻¹. The discovery of BD+14 4559 b was reported in the journal ''

The Astrophysical Journal ''The Astrophysical Journal'' (''ApJ'') is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler. The journal discontinued its print edition and ...

'' on June 10, 2009.

References