Alpha Cephei
Encyclopedia
Alpha Cephei (α Cep, α Cephei) is a second magnitude star
in the constellation
of Cepheus
that is relatively close to Earth
at only 49 light years. It has the traditional name Alderamin, an Arabic name meaning "the right arm".
throughout all of Europe
, northern Asia, Canada and American cities as far south as San Diego on the west coast but not quite as far as Miami on the east coast. All other locations around the globe having a latitude greater than ± 27° North will notice that the star is always visible in the night sky. Since Alderamin has an apparent magnitude of about 2.5, the star is easily observable to the naked eye, even in light polluted
cities.
into a subgiant, probably on its way to becoming a red giant
as its hydrogen supply runs low. In 2007, the star's apparent magnitude was recalibrated at 2.5141 along with an updated parallax of 66.50 ± 0.11 mas yielding a distance of 15 parsecs or approximately 49 light years from Earth.
Given a surface temperature of 7,600 Kelvin, theoretical calculations would yield a total luminosity for the star of about 18.7L☉.Alderamin has a radius of 2.5R☉ boasting a mass that is almost twice that of the Sun
at 1.9M☉
. Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a Delta Scuti variable.
Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars. By comparison, the Sun takes almost a month to turn on its axis. α Cep is also known to emit an amount of X radiation similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity—something unexpected (though not at all unusual) for a fast rotator.
is at present. This will next occur about the year 7500 AD.
This star, along with β Cep
(Alfirk) and η Cep
(Alkidr) were Al Kawākib al Firḳ (الكوكب الفرق), meaning "the Stars of The Flock" by Ulug Beg.
In Chinese
, , meaning Celestial Hook
, refers to an asterism consisting of α Cephei, 4 Cephei, HD 194298, η Cephei
, θ Cephei
, ξ Cephei
, 26 Cephei, ι Cephei
and ο Cephei
. Consequently, α Cephei itself is known as .
was a United States Navy
Crater class cargo ship
named after the star.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
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....
of Cepheus
Cepheus (constellation)
Cepheus is a constellation in the northern sky. It is named after Cepheus, King of Aethiopia in Greek mythology. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations.-Stars:...
that is relatively close to 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...
at only 49 light years. It has the traditional name Alderamin, an Arabic name meaning "the right arm".
Visibility
With a declination in excess of 62 degrees north, Alderamin is mostly visible to observers in the northern hemisphere, though the star is still visible as far south as ± 27° South latitude, albeit just above the horizon. The star is circumpolarCircumpolar star
A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets , due to its proximity to one of the celestial poles...
throughout all of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, northern Asia, Canada and American cities as far south as San Diego on the west coast but not quite as far as Miami on the east coast. All other locations around the globe having a latitude greater than ± 27° North will notice that the star is always visible in the night sky. Since Alderamin has an apparent magnitude of about 2.5, the star is easily observable to the naked eye, even in light polluted
Light pollution
Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.The International Dark-Sky Association defines light pollution as:...
cities.
Properties
Alderamin is a white Class A star, evolving off of the main sequenceMain 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...
into a subgiant, probably on its way to becoming a red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
as its hydrogen supply runs low. In 2007, the star's apparent magnitude was recalibrated at 2.5141 along with an updated parallax of 66.50 ± 0.11 mas yielding a distance of 15 parsecs or approximately 49 light years from Earth.
Given a surface temperature of 7,600 Kelvin, theoretical calculations would yield a total luminosity for the star of about 18.7L☉.Alderamin has a radius of 2.5R☉ boasting a mass that is almost twice 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...
at 1.9M☉
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
. Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a Delta Scuti variable.
Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars. By comparison, the Sun takes almost a month to turn on its axis. α Cep is also known to emit an amount of X radiation similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity—something unexpected (though not at all unusual) for a fast rotator.
Pole star
Alderamin is located near the precessional path traced across the celestial sphere by the Earth's north pole. That means that it periodically comes within 3° of being a pole star, much as PolarisPolaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....
is at present. This will next occur about the year 7500 AD.
| Preceded by | Pole Star Pole star The term "Pole Star" usually refers to Polaris, which is the current northern pole star, also known as the North Star.In general, however, a pole star is a visible star, especially a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent... |
Succeeded by |
|---|---|---|
| Iota Cephei Iota Cephei Iota Cephei is a Class K0, third-magnitude star in the constellation Cepheus. Iota Cephei is an orange giant star located about 115 light-years from Earth. Due to precession of the equinoxes, it will become the pole star some time around 5200 CE.-External links:... |
circa 6,800 BC | Deneb Deneb Deneb is the brightest star in the constellation Cygnus and one of the vertices of the Summer Triangle. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars... |
Etymology
The name Alderamin is a contraction of the Arabic phrase الذراع اليمين að-ðirā‘ al-yamīn "the right arm," with the first definite article transliterated literally as al, as is often the case with Arabic star names.This star, along with β Cep
Beta Cephei
Beta Cephei is a third magnitude star in the constellation Cepheus. It has the traditional name Alfirk , meaning "The Flock" This star, along with α Cep and η Cep , were Al Kawākib al Firḳ , meaning "the Stars of The Flock" by Ulug Beg...
(Alfirk) and η Cep
Eta Cephei
Eta Cephei is a class K0 third-magnitude giant star in the constellation Cepheus. Eta Cephei is an orange giant star with a very high proper motion on the celestial sphere. It is about 45 light-years from Earth...
(Alkidr) were Al Kawākib al Firḳ (الكوكب الفرق), meaning "the Stars of The Flock" by Ulug Beg.
In Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
, , meaning Celestial Hook
Rooftop (Chinese constellation)
The Rooftop mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the northern mansions of the Black Tortoise.- Asterisms :...
, refers to an asterism consisting of α Cephei, 4 Cephei, HD 194298, η Cephei
Eta Cephei
Eta Cephei is a class K0 third-magnitude giant star in the constellation Cepheus. Eta Cephei is an orange giant star with a very high proper motion on the celestial sphere. It is about 45 light-years from Earth...
, θ Cephei
Theta Cephei
Theta Cephei is a Class A7, fourth-magnitude star in the constellation Cepheus. Theta Cephei is a white spectroscopic binary star, located about 135 light-years from Earth...
, ξ Cephei
Xi Cephei
Xi Cephei is a star in the constellation Cepheus. It has the traditional name Kurhah or Alkirdah or Al Kirduh, and the name was from Al Ḳurḥaḥ , an Arabic word that translated as a white spot, or blaze, in the face of a horse and other suggestion was Al Ḳirdah , the Ape.Xi Cephei belongs to...
, 26 Cephei, ι Cephei
Iota Cephei
Iota Cephei is a Class K0, third-magnitude star in the constellation Cepheus. Iota Cephei is an orange giant star located about 115 light-years from Earth. Due to precession of the equinoxes, it will become the pole star some time around 5200 CE.-External links:...
and ο Cephei
Omicron Cephei
Omicron Cephei is a binary star in the constellation of Cepheus. It consists of a less massive K-type main sequence star in orbit with a more massive G-type giant star. The overall apparent visual magnitude of the system is 4.75.The pair was first determined to be binary by F. G. W. Struve...
. Consequently, α Cephei itself is known as .
Namesakes
USS Alderamin (AK-116)USS Alderamin (AK-116)
USS Alderamin was an Crater-class cargo ship commissioned by the U.S. Navy for service in World War II, named after Alderamin, the alpha star in constellation Cepheus. She was responsible for delivering troops, goods and equipment to locations in the war zone.SS J. S...
was a United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
Crater class cargo ship
Crater class cargo ship
Crater-class cargo ship is a category of freighter that was constructed for use by the United States Navy during World War II under Maritime Commission EC2-S-C1 type....
named after the star.
See also
- List of nearest bright stars
- Lists of stars in the constellation Draco
- Class A Stars
- Dwarf starDwarf starThe term dwarf star refers to a variety of distinct classes of stars.* Dwarf star alone generally refers to any main sequence star, a star of luminosity class V.** Red dwarfs are low-mass main sequence stars....
External links
- Jim Kaler's Stars, University of Illinois:ALDERAMIN (Alpha Cephei)
- NASA's: History of Precession
- Crystalinks:Precession of the Equinoxes