AB Pictoris (abbreviated AB Pic, also catalogued as HD 44627) is a

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 ...

, located 163.5

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 away in the southern

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 first constellati ...

of Pictor. It has been identified as a member of the young (30 million years old) Tucana–Horologium association.. The star has been classified as a

BY Draconis variable BY Draconis variables are variable stars of late spectral types, usually K or M, and typically belong to the main sequence. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in thei ...

, indicating it has an active chromosphere. It is an X-ray source and displays

emission line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...

s in its

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 ...

. In 2005 it was announced that an astronomical object (AB Pictoris b, abbreviated AB Pic b) had been imaged in 2003 and 2004 close to and apparently in orbit around the star. Its mass suggests that it is at the borderline between being a

brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...

or a

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 ...

Planetary system

In 2003 and 2004, an object (now catalogued as ''AB Pictoris b'') was observed close to the star by a team of astronomers at the

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 m ...

. Since it had

common proper motion This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of astronomical object, celestial objects and phenomena ...

with AB Pictoris, it was concluded that it was physically close to the star. Its

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

was estimated as between L0V and L3V. Using evolutionary models, its mass was estimated as from 13 to 14 Jupiter masses. However, because modelling such young objects is difficult, this estimate is very uncertain; some models give masses as low as 11 Jupiter masses or as high as 70 Jupiter masses. Temperature estimates range from 1600 K to 2400 K. As it is not known if the mass of the object exceeds the deuterium burning limit of 13 Jupiter masses, it is not clear whether the object should be classified as an

extrasolar planet 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 detect ...

or a

. In 2010 a team obtained the spectrum of AB Pic b with VLT/SINFONI. This confirmed this object as an L-dwarf with low surface gravity, matching a spectral type of L0-L1. It also constrained the temperature to

Kelvin The kelvin (symbol: K) is the base unit for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts at the lowest possible temperature (absolute zero), taken to be 0 K. By de ...

. Another team found that AB Pic b has a lower temperature of 1400-1700 K and possibly a lower mass (7-14 , from figure 13). A later analysis did find a temperature of K and a mass of 10-14 . The planet shows several molecular and atomic absorption lines in the spectrum. The most notable are

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

and

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

. The planetary orbit is significantly misaligned with its spin axis orientation (obliquity), possibly due to gravitational interactions with the additional inner planet. An additional planet, AB Pictoris c, was first suspected by combining direct imaging, radial velocity and the astrometric acceleration from AB Pic A. The planet was confirmed in 2025 with a re-analysis of the Gaia excess noise and the proper motion anomaly.

References

External links

* * Homogeneous comparison of directly detected planet candidates: GQ Lup, 2M1207, AB Pic, Ralph Neuhaeuser, ''ESO Workshop Proceedings on Multiple Stars'', , . * {{DEFAULTSORT:AB Pictoris K-type main-sequence stars BY Draconis variables Astronomical X-ray sources Planetary systems with one confirmed planet Pictor CD-58 01409 030034 044627 Pictoris, AB

Planetary system

See also

References

External links