Delta Tauri
Encyclopedia
The Bayer designation
Delta Tauri (δ Tau, δ Tauri) is shared by three star systems in the constellation
Taurus
. They are all members of the Hyades
star cluster
.
Because they are close to the ecliptic
, these stars can be occulted by the Moon
and, very rarely, by planet
s. The last occultation of δ¹ Tauri by a planet took place on 3 January 1818, when it was occulted by Venus
.
and has the traditional name Hyadum II, which is Latin
for "Second Hyad", and the name Eudora
(Greek
Ευδωρη), who was one of the Hyades sisters.
The primary component, Delta-1 Tauri A, is an orange K-type
giant
with an apparent magnitude
of +3.77. Delta-1 has a luminosity
of 74 times that of the Sun
and a radius of 11.6 times solar. Its mass is calculated to be 2.6 solar mass
es. The surface temperature of this star is 4965 kelvin
s. Its companion, Delta-1 Tauri B, is a 12th magnitude star separated by 107 arcseconds from the primary. It is most likely not physically related to the main star. However, observations of lunar occultation
s of this star has revealed a much closer, physically related, star that orbits the main star in an eccentric orbit
with an average distance of 1.76 AU
. This companion takes about 530 days to orbit the main star.
main sequence dwarf
with an apparent magnitude
of +4.80. It is approximately 146 light years
from Earth
and is separated from δ¹ Tauri by 0.23° on the sky.
Taurus
. It is approximately 148 light years
from Earth
and is separated from δ¹ Tauri by 0.72° on the sky. This star also has the traditional name Cleeia or Kleeia (Greek
Κλεεια), who was one of the Hyades sisters.
The primary component, δ³ Tauri A, is a white A-type
subgiant with a mean apparent magnitude
of +4.30. It is classified as an Alpha2 Canum Venaticorum type
variable star
and its brightness varies from magnitude +4.29 to +4.32 with a period of 57.25 days. It has a close, 8th magnitude binary companion, δ³ Tauri B, 1.4 arcseconds, or at least 64 Astronomical Unit
s, away. At 77 arcseconds away is the third component, the 11th magnitude δ³ Tauri C.
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...
Delta Tauri (δ Tau, δ Tauri) is shared by three star systems in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Taurus
Taurus (constellation)
Taurus is one of the constellations of the zodiac. Its name is a Latin word meaning 'bull', and its astrological symbol is a stylized bull's head:...
. They are all members of the Hyades
Hyades (star cluster)
The Hyades is the nearest open cluster to the Solar System and one of the best-studied of all star clusters. The Hipparcos satellite, the Hubble Space Telescope, and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster's center of ~153 ly...
star cluster
Open cluster
An open cluster is a group 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 many more are thought to exist...
.
Because they are close to the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
, these stars can be occulted by the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and, very rarely, by planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s. The last occultation of δ¹ Tauri by a planet took place on 3 January 1818, when it was occulted by Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
.
δ¹ Tauri
δ¹ Tauri is a triple star approximately 153 light years from EarthEarth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and has the traditional name Hyadum II, which is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "Second Hyad", and the name Eudora
Eudora
Eudora may refer to:Places*Eudora, Arkansas, a city*Eudora, Kansas, a city*Eudora Township, Douglas County, Kansas*Eudora, Mississippi, an unincorporated community*Eudora, Missouri, an unincorporated community*217 Eudora, an asteroidOther...
(Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
Ευδωρη), who was one of the Hyades sisters.
The primary component, Delta-1 Tauri A, is an orange K-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
giant
Giant star
A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...
with an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +3.77. Delta-1 has a luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
of 74 times that of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
and a radius of 11.6 times solar. Its mass is calculated to be 2.6 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es. The surface temperature of this star is 4965 kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
s. Its companion, Delta-1 Tauri B, is a 12th magnitude star separated by 107 arcseconds from the primary. It is most likely not physically related to the main star. However, observations of lunar occultation
Occultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...
s of this star has revealed a much closer, physically related, star that orbits the main star in an eccentric orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
with an average distance of 1.76 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. This companion takes about 530 days to orbit the main star.
δ² Tauri
δ² Tauri is a white A-typeStellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
main sequence dwarf
Main sequence
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 Hertzsprung and Henry Norris Russell...
with an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +4.80. It is approximately 146 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....
from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and is separated from δ¹ Tauri by 0.23° on the sky.
δ³ Tauri
δ³ Tauri is a triple star system in the constellationConstellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Taurus
Taurus (constellation)
Taurus is one of the constellations of the zodiac. Its name is a Latin word meaning 'bull', and its astrological symbol is a stylized bull's head:...
. It is approximately 148 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....
from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and is separated from δ¹ Tauri by 0.72° on the sky. This star also has the traditional name Cleeia or Kleeia (Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
Κλεεια), who was one of the Hyades sisters.
The primary component, δ³ Tauri A, is a white A-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
subgiant with a mean apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +4.30. It is classified as an Alpha2 Canum Venaticorum type
Alpha2 Canum Venaticorum variable
An Alpha2 Canum Venaticorum variable is a type of variable star. These stars are chemically peculiar main sequence stars of spectral class B8p to A7p. They have strong magnetic fields and strong silicon, strontium, or chromium spectral lines...
variable star
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
and its brightness varies from magnitude +4.29 to +4.32 with a period of 57.25 days. It has a close, 8th magnitude binary companion, δ³ Tauri B, 1.4 arcseconds, or at least 64 Astronomical Unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s, away. At 77 arcseconds away is the third component, the 11th magnitude δ³ Tauri C.