Pictor

Pictor is a constellation in the Southern Celestial Hemisphere, located between the star Canopus and the Large Magellanic Cloud. Its name is Latin for painter, and is an abbreviation of the older name Equuleus Pictoris (the "painter's easel"). Normally represented as an easel, Pictor was named by Abbé Nicolas-Louis de Lacaille in the 18th century. The constellation's brightest star is Alpha Pictoris, a white main-sequence star around 97 light-years away from Earth. Pictor also hosts RR Pictoris, a cataclysmic variable star system that flared up as a nova, reaching apparent (visual) magnitude 1.2 in 1925 before fading into obscurity. Pictor has attracted attention because of its second-brightest star Beta Pictoris, 63.4 light-years distant from Earth, which is surrounded by an unusual dust disk rich in carbon, as well as three exoplanets (extrasolar planets). Another five stars in the constellation have been observed to have planets. Among them is HD 40307, an orange dwarf that has six planets orbiting it, one of which—HD 40307 g—is a potential super-Earth in the circumstellar habitable zone. Kapteyn's Star, the nearest star in Pictor to Earth, is a red dwarf located 12.76 light-years away that was believed to have two super-Earths in orbit in 2014, but their existence of these planets was disproven in 2021. Pictor A is a radio galaxy that is shooting an 800,000 light-year long jet of plasma from a supermassive black hole at its centre. In 2006, a gamma-ray burst—GRB 060729—was observed in Pictor, its extremely long X-ray afterglow detectable for nearly two years.

History

The French astronomer Abbé Nicolas-Louis de Lacaille first described Pictor as le Chevalet et la Palette (the easel and palette) in 1756, after observing and cataloguing 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised 14 new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honored instruments that symbolised the Age of Enlightenment. He gave these constellations Bayer designations, including ten stars in Pictor now named Alpha to Nu Pictoris. He labelled the constellation Equuleus Pictorius on his 1763 chart, the word "Equuleus" meaning small horse, or easel—perhaps from an old custom among artists of carrying a canvas on a donkey. The German astronomer Johann Bode called it Pluteum Pictoris. The name was shortened to its current form in 1845 by the English astronomer Francis Baily on the suggestion of his countryman Sir John Herschel.

Characteristics Pictor is a small constellation bordered by Columba to the north, Puppis and Carina to the east, Caelum to the northwest, Dorado to the southwest and Volans to the south. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Pic". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 18 segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 04h 32.5m and 06h 52.0m , while the declination coordinates are between −42.79° and −64.15°. Pictor culminates each year at 9 p.m. on 17 March. Its position in the far Southern Celestial Hemisphere means that the whole constellation is visible to observers south of latitude 26°N, and parts become circumpolar south of latitude 35°S.

Features

Stars

Pictor is a faint constellation; its three brightest stars can be seen near the prominent Canopus. Within the constellation's borders, there are 49 stars brighter than or equal to apparent magnitude 6.5. At apparent magnitude 3.3, Alpha Pictoris is the brightest star in the constellation; it is an astrometric binary 97 light-years from Earth. The primary of this system is an A-type star of spectral type A8VnkA6, a rapidly spinning star with a projected rotational velocity estimated at 206 km/s with has a shell of circumstellar gas. Beta Pictoris is another white main sequence star of spectral type A6V and apparent magnitude 3.86. Located around 63.4 light-years distant from Earth, it is a member of the Beta Pictoris moving group—a group of 17 star systems around 12 million years old moving through space together. In 1984 Beta Pictoris was the first star discovered to have a debris disk. Since then, two exoplanets with masses over ten times the mass of Jupiter have been discovered orbiting between 2.7 and eight astronomical units (AU) away from the star, which fit between the asteroid belt and the orbit of Saturn. Beta Pictoris b was discovered using direct imagery with the Very Large Telescope in late 2009, while Beta Pictoris c was discovered via doppler spectroscopy (radial velocity method) in August 2009. A third planet with a lower mass of 2-3 times the mass of Jupiter, Beta Pictoris d, was discovered in 2026 using direct imaging and spectral template matching with moderate-resolution spectroscopy. Gamma Pictoris is an orange giant of spectral type K1III that has swollen to 11 times the diameter of the Sun. Shining with an apparent magnitude of 4.5, it lies 186 light-years distant from Earth. HD 42540, called 47 Pictoris by American astronomer Benjamin Apthorp Gould, is a slightly cooler orange giant, with a spectral type of K2.5III and average magnitude 5.04. It has also been suspected of being a variable star. Lacaille mistakenly named this star Mu Doradus, but had recorded its Right Ascension one hour too low. Lacaille named two neighbouring stars Eta Pictoris. Eta2 Pictoris, also known as HR 1663, is an orange giant of spectral type K5III and apparent magnitude 5.05. 474 light-years distant, it has a diameter 5.6 times that of the Sun. Eta1 Pictoris, also known as HR 1649, is 85 light-years distant and is a main sequence star of spectral type F5V and visual magnitude 5.38. A double star, it has a companion of magnitude 13; the two are separated by 11 arcseconds.

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