Electra , designated 17 Tauri, is a blue-white giant

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 ...

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 ...

Taurus Taurus is Latin for 'bull' and may refer to: * Taurus (astrology), the astrological sign * Taurus (constellation), one of the constellations of the zodiac * Taurus (mythology), one of two Greek mythological characters named Taurus * ''Bos taurus ...

. It is the third-brightest star in the

Pleiades The Pleiades (), also known as The Seven Sisters, Messier 45 and other names by different cultures, is an asterism and an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance of ...

open star cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

( M45); the most visible stars in this group are named for the Seven Sisters of

Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...

Properties

The star has an apparent brightness of 3.72, the third-brightest of the stars in the group. Electra belongs to the spectral class B6 IIIe and is approximately 400

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 from the Sun. The Pleiades cluster is thought to be 444 light-years away. The

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

of this star is 181 km/s, making it a fast rotator. This is the velocity component of the star's equatorial rotation along the line of sight to the Earth. The estimated inclination of the star's pole is , giving it a true equatorial rotational velocity of . The rapid rotation rate of this star flattens the poles and stretch the equator. This makes the surface gravity of the star non-uniform and causes temperature variation. This effect is known as

gravity darkening Gravity darkening, also referred to as gravity brightening, is an astronomical phenomenon where the poles of a star are brighter than the equator, due to rapid rotation and oblate shape. When a star is oblate, it has a larger radius at its equat ...

, because it results in a variation of radiation by latitude. The rapid rotation extends the life span of the star by increasing the core density and reducing the radiation output. This is classified as a

Be star Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer e ...

, which is a

B-type star A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type stars ...

with prominent emission lines of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

in its spectrum. The Be stars have a rotation rate that is 1.5–2 times the rotation of normal B-type stars. This high rate of rotation may allow mass loss during even minor prominences. Changes in the

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

measurements indicate that this star may have a companion, which would make Electra a

spectroscopic binary A binary star is a system of two star, stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separa ...

. However, follow-up studies including

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

have failed to confirm any companion star(s), so it is likely a single star. ElectraLightCurve

Electra may be a variable star, and it appears in the

New Catalogue of Suspected Variable Stars The ''New Catalogue of Suspected Variable Stars'' (NSV) is a star catalogue containing 14,811 stars which, although suspected to be variable, were not given variable star designations In astronomy, a variable star designation is a unique identifi ...

as NSV 15755. Low amplitude variability of the brightness of Electra was detected by Kepler/K2, and Fourier analysis of the star's light curve shows several periods of oscillation, the strongest being 1.107 and 1.165 days. The International Variable Star Index classifies it as a

slowly pulsating B star A slowly pulsating B-type star (SPB), formerly known as a 53 Persei variable, is a type of pulsating variable star. They may also be termed a long-period pulsating B star (LPB). As the name implies, they are main-sequence stars of spectral type B2 ...

Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

observations of this star showed an excess level of radiation equal to about 0.5 magnitudes. This emission is probably from a gaseous disk created by radiation-driven mass loss and rapid rotation of the star. These disks are created by an ejection of material roughly every ten years, which then settles into the equatorial plane about the star. However, the bright nebulosity that surrounds this star makes the observation uncertain.

Nomenclature

''17 Tauri'' is the star's

Flamsteed designation A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the modern constellations visible from southern England. They are named for John Flamsteed who first used them while co ...

. It bore the traditional name ''Electra''.

Electra Electra (; grc, Ήλέκτρα) is one of the most popular mythological characters in tragedies.Evans (1970), p. 79 She is the main character in two Greek tragedies, '' Electra'' by Sophocles and '' Electra'' by Euripides. She is also the centra ...

was one of the Pleiades sisters in

. In 2016, the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name ''Electra'' for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.

Military namesakes

USS ''Electra'' (1843) and USS ''Electra'' (AK-21/AKA-4), both of

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

References

External links

* {{DEFAULTSORT:Electra (Star) B-type giants Tauri, 017 Pleiades Open Cluster

Taurus (constellation) Be stars

1142 Year 1142 ( MCXLII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. Events By place Byzantine Empire * Spring – Emperor John II Komnenos and his sons lead a Byzantine expedi ...

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