L₂ Puppis (also known as HD 56096) is a

giant star A giant star is a star with substantially larger radius and luminosity than a main sequence, main-sequence (or ''dwarf'') star of the same effective temperature, surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moo ...

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 ...

Puppis Puppis is a constellation in the southern sky. Puppis, the Latin translation of "poop deck", was originally part of an over-large constellation Argo Navis (the ship of Jason and the Argonauts), which centuries after its initial description, was ...

and is located between the bright

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 ...

Canopus Canopus is the brightest star in the southern constellation of Carina (constellation), Carina and the list of brightest stars, second-brightest star in the night sky. It is also Bayer designation, designated α Carinae, which is Lat ...

and

Sirius Sirius is the list of brightest stars, brightest star in the night sky. Its name is derived from the Ancient Greek language, Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinisation ...

. It is a semi-regular pulsating star. The designation L₂ has a tangled history. This star and another were both labelled with "L" by

Nicolas-Louis de Lacaille Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a kingdom of France, French astronomer and geodesist who named 14 out of the IAU designated constellations, 88 constellations. From 1750 ...

when he created the constellation Puppis within

Argo Navis Argo Navis (the Ship Argo), or simply Argo, is one of the 48 Ptolemy's constellations, now a grouping of three IAU constellations. It is formerly a single large constellation in the southern sky. The genitive is "Argus Navis", abbreviated "Arg". ...

. The two stars were labelled as "1.L" and "2.L" by

Johann Elert Bode Johann Elert Bode (; 19 January 1747 – 23 November 1826) was a German astronomer known for his reformulation and popularisation of the Titius–Bode law. Bode determined the orbit of Uranus and suggested the planet's name. Life and career Bo ...

in his star catalogue published in 1801. Later authors used L1 and L2, usually with numeric subscripts (i.e. L₁ and L₂), but occasionally as superscripts. The subscripted designation is now universally used where typography allows for subscripts. L₂ Puppis was discovered to be variable by

Benjamin Apthorp Gould Benjamin Apthorp Gould (September 27, 1824 – November 26, 1896) was a pioneering American astronomer. He is noted for creating the ''Astronomical Journal'', discovering the Gould Belt, and for founding of the Argentine National Observatory an ...

in 1872, and was listed in Uranometria Argentina as 73 G. Puppis with magnitude 5.10v. It has never been given a formal

variable star designation In astronomy, a variable star designation is a unique identifier given to variable stars. It uses a variation on the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constell ...

, unlike L₁ Puppis which is OU Puppis. L2PupLightCurve

L₂ Puppis varies in

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 ...

by about two magnitudes with a period of 140 days. The average brightness also varies slowly over several years so that the total range is given as magnitude 2.6–6.0. Since 1995 the average brightness has dropped so that the 140-day variations are now between about magnitude 6 and 8. The variation in light may be caused by a combination of radial pulsations in the star's atmosphere and by dimming from

circumstellar dust Circumstellar dust is cosmic dust around a star. It can be in the form of a spherical shell or a disc, e.g. an accretion disk. Circumstellar dust can be responsible for significant extinction and is usually the source of an infrared excess for sta ...

. L₂ Puppis is most likely an

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

star that has passed through 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 ...

and is evolving to become a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

. It is shedding mass at the rate of about per year, forming a circumstellar dust disk and bipolar plumes of gas that are thought to be the start of a "butterfly"-type

planetary nebula A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to ...

. It has been calculated that the mass of L₂ Puppis is currently about and its original mass was close to about 10 billion years ago. Other calculations give higher masses, for example , and younger ages such as 1.5 billion years. A candidate

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 ...

has been found orbiting L₂ Puppis every 4.69 years at a distance of . The mass is highly uncertain, at , and it might just be a dense clump of gas and dust. L₂ Puppis has a visual 12th-magnitude companion. A hundred years ago, they were separated by about a

minute of arc A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

, but different

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

s mean that this is now about .

References

{{DEFAULTSORT:Hd 56096 Puppis Semiregular variable stars M-type giants Puppis, L2 056096 Post-asymptotic-giant-branch stars 034922 2748 Emission-line stars Durchmusterung objects Puppis, 73