Beta Doradus, Latinized from β Doradus, is the second brightest star 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 origins of the e ...

Dorado Dorado () is a constellation in the southern sky. It was named in the late 16th century and is now one of the 88 modern constellations. Its name refers to the dolphinfish (''Coryphaena hippurus''), which is known as ''dorado'' in Spanish, altho ...

. It has a variable

apparent visual 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 lig ...

, and is visible to the naked eye from the southern hemisphere. Based upon

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

measurements with the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

, it is located at a distance of from Earth. BetaDorLightCurve

Beta Doradus is a

Cepheid variable A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid varia ...

that regularly changes magnitude from a low of 4.08 to a high of 3.46 over a period of 9.84318 days. The

light curve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

of this magnitude change follows a nearly regular saw-tooth pattern, with average amplitude variations period to period about 0.005

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

from average amplitude of 0.62

. During each radial pulsation cycle, the radius of the star varies by ±3.9 times the Sun's radius around a mean of 67.8. Its

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

and

luminosity class 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 ...

are likewise variable, from F-type to G-type and from a

supergiant Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spa ...

to a

bright giant A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

. Far

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

emissions have been detected from this star with the

Far Ultraviolet Spectroscopic Explorer Far Ultraviolet Spectroscopic Explorer (FUSE, Explorer 77, and MIDEX-0) represented the next generation, high-orbit, ultraviolet space observatory covering the wavelength range of 90.5–119.5 nanometre (nm) of the NASA operated by the Johns Ho ...

, while

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

emissions were detected with the

XMM-Newton ''XMM-Newton'', also known as the High Throughput X-ray Spectroscopy Mission and the X-ray Multi-Mirror Mission, is an X-ray space observatory launched by the European Space Agency in December 1999 on an Ariane 5 rocket. It is the second cornerst ...

space telescope. The X-ray luminosity is about 1 × 10²⁹

erg The erg is a unit of energy equal to 10−7joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' o ...

/s and the emission varies with the pulsation period, suggesting a connection with the pulsation process. The peak X-ray emissions are in the 0.6–0.8

keV Kev can refer to: Given name * Kev Adams, French comedian, actor, screenwriter and film producer born Kevin Smadja in 1991 * Kevin Kev Carmody (born 1946), Indigenous Australian singer-songwriter * Kev Coghlan (born 1988), Scottish Grand Prix motor ...

energy range, which occurs for plasmas with temperatures of 7–10 million K.

References

{{DEFAULTSORT:Beta Doradus F-type supergiants Classical Cepheid variables Dorado (constellation) Doradus, Beta CD-62 00214 037350 026069

1922 Events January * January 7 – Dáil Éireann (Irish Republic), Dáil Éireann, the parliament of the Irish Republic, ratifies the Anglo-Irish Treaty by 64–57 votes. * January 10 – Arthur Griffith is elected President of Dáil Éirean ...