BD+14 4559 b, named Pirx, is 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 ...

orbiting the

K-type main sequence star A K-type main-sequence star, also referred to as a K-type dwarf or an 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 ...

BD+14 4559 about 161

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 (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 ( grc-gre, Πήγασος, Pḗgasos; la, Pegasus, Pegasos) is one of the best known creatures in Greek mythology. He is a winged divine stallion usually depicted as pure white in color. He was sired by Poseidon, in his role as hor ...

. It orbits its star within 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 ...

at a distance of 0.777 AU, close to that 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 ...

, 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 t ...

, from radial-velocity measurements via observation of

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 ...

s in the

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

of the

planet 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 you ...

's parent star. The planet was named during the

NameExoWorlds NameExoWorlds (also known as IAU NameExoWorlds) is the name of various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, which would later be considered for official ad ...

campaign by

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populous ...

Pilot Pirx Pilot Pirx is a fictional character introduced in 1966 in the science fiction stories of Polish writer Stanisław Lem: ten short stories (published in English in two parts, 1979's ''Tales of Pirx the Pilot'' and 1982's ''More Tales of Pirx the Pilo ...

is a fictional character from stories by Polish

science-fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel univers ...

writer

Stanisław Lem Stanisław Herman Lem (; 12 September 1921 – 27 March 2006) was a Polish writer of science fiction and essays on various subjects, including philosophy, futurology, and literary criticism. Many of his science fiction stories are of satirical ...

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. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...

, 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 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 ...

. 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 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 ...

named BD+14 4559. 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 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 ...

, 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 t ...

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 result ...

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 10-meter (30-foot) aperture 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 numb ...

. 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'', often abbreviated ''ApJ'' (pronounced "ap jay") in references and speech, is a peer-reviewed Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work ...

'' on June 10, 2009.

References