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Spica

Spica

Overview
Spica is the brightest star
Brightest Star
-Information:Debut mini-album from vocal group Bright. This was their first cd they released under major label Rhythm Zone. The album ranked weekly on the Oricon chart at #133.- Track listing :#Theme of Bright#Brightest Star#Girls Party Time#Eternal Love#Tears...

 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....

 Virgo
Virgo (constellation)
Virgo is one of the constellations of the zodiac. Its name is Latin for virgin, and its symbol is . Lying between Leo to the west and Libra to the east, it is the second largest constellation in the sky...

, and the 15th brightest star in the nighttime sky. It is 260 light years distant 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...

. A blue giant
Blue giant
In astronomy, a blue giant is a star with a spectral type of O or B and a luminosity class of III...

, it is a variable
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...

 of the Beta Cephei type
Beta Cephei variable
Beta Cephei variables are variable stars which exhibit variations in their brightness due to pulsations of the stars' surfaces. The point of maximum brightness roughly corresponds to the maximum contraction of the star. Typically, Beta Cephei variables change in brightness by 0.01 to 0.3...

.

Spica is believed to be the star that provided Hipparchus
Hipparchus
Hipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...

 with the data which enabled him to discover precession of the equinoxes. A temple
Temple
A temple is a structure reserved for religious or spiritual activities, such as prayer and sacrifice, or analogous rites. A templum constituted a sacred precinct as defined by a priest, or augur. It has the same root as the word "template," a plan in preparation of the building that was marked out...

 to Menat (an early Hathor
Hathor
Hathor , is an Ancient Egyptian goddess who personified the principles of love, beauty, music, motherhood and joy. She was one of the most important and popular deities throughout the history of Ancient Egypt...

) at Thebes
Thebes, Egypt
Thebes is the Greek name for a city in Ancient Egypt located about 800 km south of the Mediterranean, on the east bank of the river Nile within the modern city of Luxor. The Theban Necropolis is situated nearby on the west bank of the Nile.-History:...

 was oriented with reference to Spica when it was constructed in 3200 BC and, over time, precession resulted in a slow but noticeable change in the location of Spica relative to the temple.
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Encyclopedia
Spica is the brightest star
Brightest Star
-Information:Debut mini-album from vocal group Bright. This was their first cd they released under major label Rhythm Zone. The album ranked weekly on the Oricon chart at #133.- Track listing :#Theme of Bright#Brightest Star#Girls Party Time#Eternal Love#Tears...

 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....

 Virgo
Virgo (constellation)
Virgo is one of the constellations of the zodiac. Its name is Latin for virgin, and its symbol is . Lying between Leo to the west and Libra to the east, it is the second largest constellation in the sky...

, and the 15th brightest star in the nighttime sky. It is 260 light years distant 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...

. A blue giant
Blue giant
In astronomy, a blue giant is a star with a spectral type of O or B and a luminosity class of III...

, it is a variable
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...

 of the Beta Cephei type
Beta Cephei variable
Beta Cephei variables are variable stars which exhibit variations in their brightness due to pulsations of the stars' surfaces. The point of maximum brightness roughly corresponds to the maximum contraction of the star. Typically, Beta Cephei variables change in brightness by 0.01 to 0.3...

.

Observation history


Spica is believed to be the star that provided Hipparchus
Hipparchus
Hipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...

 with the data which enabled him to discover precession of the equinoxes. A temple
Temple
A temple is a structure reserved for religious or spiritual activities, such as prayer and sacrifice, or analogous rites. A templum constituted a sacred precinct as defined by a priest, or augur. It has the same root as the word "template," a plan in preparation of the building that was marked out...

 to Menat (an early Hathor
Hathor
Hathor , is an Ancient Egyptian goddess who personified the principles of love, beauty, music, motherhood and joy. She was one of the most important and popular deities throughout the history of Ancient Egypt...

) at Thebes
Thebes, Egypt
Thebes is the Greek name for a city in Ancient Egypt located about 800 km south of the Mediterranean, on the east bank of the river Nile within the modern city of Luxor. The Theban Necropolis is situated nearby on the west bank of the Nile.-History:...

 was oriented with reference to Spica when it was constructed in 3200 BC and, over time, precession resulted in a slow but noticeable change in the location of Spica relative to the temple. Nicolaus Copernicus
Nicolaus Copernicus
Nicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....

 made many observations of Spica with his home-made triquetrum
Triquetrum (astronomy)
The triquetrum was the medieval name for an ancient astronomical instrument first described by Ptolemy in the Almagest . Also known as Parallactic Rulers, it was used for determining altitudes of heavenly bodies...

 for his researches on precession.

As one of the nearest massive binary star systems to the Sun, Spica has been the subject of many observational studies.

Characteristics


Spica is a close binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 whose components orbit about each other every four days. They remain sufficiently close together that they can not be resolved as individual stars through a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

. The changes in the orbital motion of this pair results in a Doppler shift in the absorption lines of their respective spectra
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...

, making them a double-lined spectroscopic binary. Initially, the orbital parameters for this system were inferred using spectroscopic measurements. Between 1966 and 1970, the Narrabri interferometer was used to observe the pair, and to directly measure the orbital characteristics and the angular diameter of the primary. The latter was determined to be , while the angular size of the semimajor axis of the orbit was found to be only slightly larger at .

The primary star has a stellar classification
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...

 of B1 III-IV. The luminosity class matches the spectrum of a star that is midway between a subgiant and a giant star
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...

, and it is no longer a B-type main sequence star. This is a massive star with more than 10 times the mass of the Sun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

 and seven times the Sun's radius. The total luminosity of this star is about 12,100 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 eight times the luminosity of its companion. The primary is one of the nearest stars to the Sun that has sufficient mass to end its life in a Type II supernova
Type II supernova
A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least 9 times, and no more than 40–50 times the mass of the Sun for this type of explosion. It is distinguished from other types of supernova by the presence of hydrogen in its spectrum...

 explosion.

The primary is classified as a Beta Cephei type
Beta Cephei variable
Beta Cephei variables are variable stars which exhibit variations in their brightness due to pulsations of the stars' surfaces. The point of maximum brightness roughly corresponds to the maximum contraction of the star. Typically, Beta Cephei variables change in brightness by 0.01 to 0.3...

 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...

 that varies in brightness over a 0.1738 day period. The spectrum shows a radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...

 variation with the same period, indicating that the surface of the star is regularly pulsating outward and then contracting. This star is rotating rapidly, with a rotational velocity of 199 km/s along the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

.

The secondary member of this system is one of the few stars to display the Struve-Sahade Effect
Struve-Sahade effect
The Struve-Sahade effect occurs with a double-lined spectroscopic binary star system. A spectroscopic binary is called double-lined when the absorption lines of both stars can be observed with a spectroscope...

. This is an anomalous change in the strength of the spectral line
Spectral line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from a deficiency or excess of photons in a narrow frequency range, compared with the nearby frequencies.- Types of line spectra :...

s over the course of an orbit, where the lines become weaker as the star is moving away from the observer. It may be caused by a strong stellar wind
Stellar wind
A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.Different types of stars have...

 from the primary scattering the light from secondary when it is receding. This star is smaller than the primary, with about 7 times the mass of the Sun and 3.6 times the Sun's radius. Its stellar classification is B2 V, making this a main sequence star.

Spica is a rotating ellipsoidal variable
Rotating ellipsoidal variable
Rotating ellipsoidal variables are a class of variable star. They are close binary systems whose components are ellipsoidal. They are not eclipsing, but fluctuations in apparent magnitude occur due to changes in the amount of light emitting area visible to the observer...

, which is a non-eclipsing close binary star system where the stars are mutually distorted through their gravitational interaction. This effect causes the 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 the star system to vary by 0.03 over a time interval that matches the orbital period. This slight dip in magnitude is barely noticeable visually. The rotation rates of both stars are faster than their mutual orbital period. This lack of synchronization and the high ellipticity of their orbit may indicate that this is a young star system. Over time, the mutual tidal interaction of the pair may lead to rotational synchronization and orbit circularization.

Visibility




Located 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...

, Spica can be occulted
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...

 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 sometimes by the 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 planetary occultation of Spica occurred when 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...

 passed in front of the star (as seen 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...

) on November 10, 1783. The next occultation will occur on September 2, 2197, when Venus again passes in front of Spica. The Sun passes a little more than 2° north of Spica around October 16 every year, and the star's heliacal rising
Heliacal rising
The heliacal rising of a star occurs when it first becomes visible above the eastern horizon for a brief moment just before sunrise, after a period of time when it had not been visible....

 occurs about two weeks later. Every 8 years, Venus passes Spica around the time of the star's heliacal rising, as in 2009 when it passed 3.5° north of the star on November 3.

A method of finding Spica is to follow the arc of the handle of the Big Dipper
Big Dipper
The Plough, also known as the Big Dipper or the Saptarishi , is an asterism of seven stars that has been recognized as a distinct grouping in many cultures from time immemorial...

 to Arcturus, and then continue on the same angular distance
Angular distance
In mathematics and all natural sciences , the angular distance between two point objects, as observed from a location different from either of these objects, is the size of the angle between the two directions originating from...

 to Spica. This can be recalled by the mnemonic phrase, "follow the arc to Arcturus and speed on to Spica."

Etymology and cultural significance



The name Spica derives from 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...

 spīca virginis "Virgo's ear of grain" (usually wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

). In Chinese astronomy, the star is known as Jiao Xiu 1 (角宿一) in Jiao Xiu
Horn (Chinese constellation)
The Horn mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the eastern mansions of the Azure Dragon.-Asterisms:...

, one of the Chinese constellation
Chinese constellation
Chinese constellations are the way the ancient Chinese grouped the stars. They are very different from the modern IAU recognized constellations. This is because the IAU was based on Greco-Roman astronomy instead of Chinese astronomy....

s. In Hindu
Hindu
Hindu refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is also attributed to all persons professing any Indian religion...

 astronomy
Hindu calendar
The hindu calendar used in ancient times has undergone many changes in the process of regionalization, and today there are several regional Indian calendars, as well as an Indian national calendar. Nepali calendar, Bengali calendar, Malayalam calendar, Tamil calendar, Telugu calendar, Kannada...

, Spica corresponds to the Nakshatra
Nakshatra
Nakshatra is the term for lunar mansion in Hindu astrology. A nakshatra is one of 27 sectors along the ecliptic...

 Chitra
Chitra
Chitra is a Sanskrit adjective meaning "excellent, distinguished; bright, bright-coloured". As a noun, it may refer to:* Chitra, the Sanskrit name of Spica virginis**in Hindu astrology, the corresponding nakshatra ....

. The 17th century German astronomer Bayer and others referred to the star as Arista.

Medieval names include Azimech, from Arabic السماك الأعزل al-simāk al-a‘zal 'the Undefended', and Alarph, Arabic for 'the Grape Gatherer'. Other titles include Sumbalet, Sombalet, Sembalet Eleandri, Shibbōleth, Citrā, Sa-Sha-Shirū, Kió, Repā.

In medieval astrology
Astrology
Astrology consists of a number of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world...

, it was a Behenian fixed star, associated with the emerald
Emerald
Emerald is a variety of the mineral beryl colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the 10 point Mohs scale of mineral hardness...

 and sage
Common sage
Salvia officinalis is a small, perennial, evergreen subshrub, with woody stems, grayish leaves, and blue to purplish flowers. It is a member of the family Lamiaceae and is native to the Mediterranean region, though it has naturalized in many places throughout the world...

. In his Three Books of Occult Philosophy, Cornelius Agrippa attributes its kabbalistic symbol to Hermes Trismegistus
Hermes Trismegistus
Hermes Trismegistus is the eponymous author of the Hermetic Corpus, a sacred text belonging to the genre of divine revelation.-Origin and identity:...

.

A blue star represents Spica on the flag of the Brazilian state of Pará. Spica is also the star representing Pará on the Brazilian flag.

Spica was used in the novel Pushing Ice
Pushing Ice
Pushing Ice is a 2005 science fiction novel by Welsh author Alastair Reynolds. According to Reynolds' Web site, the story takes place in a universe separate and distinct from his Revelation Space universe.- Plot summary:...

by Alastair Reynolds
Alastair Reynolds
Alastair Preston Reynolds is a British science fiction author. He specialises in dark hard science fiction and space opera. He spent his early years in Cornwall, moved back to Wales before going to Newcastle, where he read physics and astronomy. Afterwards, he earned a PhD from St Andrews, Scotland...

 as the distant star to which the protagonists are carried by alien technology.

The Japanese manga
Manga
Manga is the Japanese word for "comics" and consists of comics and print cartoons . In the West, the term "manga" has been appropriated to refer specifically to comics created in Japan, or by Japanese authors, in the Japanese language and conforming to the style developed in Japan in the late 19th...

 and series Twin Spica
Twin Spica
is a Japanese seinen manga series written and illustrated by Kou Yaginuma. The "realistic, slice-of-life science fiction series" tells the story of a group of Japanese high school students training to become astronauts in the early 21st century after the country's first human spaceflight launch...

was named after the star. Spica is two stars that circle each other, though from a distance they appear as one, which parallels the series' running theme of friendship.

In the video game Ar Tonelico, one of the characters is named Spica.

Namesakes


Both USS Spica (AK-16)
USS Spica (AK-16)
USS Spica was an Sirus-class cargo ship commissioned by the U.S. Navy for service in World War II. She was responsible for delivering necessary goods and equipment to ships and stations in the war zone.- An extended period in mothballs :...

 and USNS Spica (T-AFS-9)
USNS Spica (T-AFS-9)
The USNS Spica was a combat stores ship acquired by the U.S. Navy in 1981. The Spica served the Navy fleet until she was deactivated in 2008.-Built in England:...

 were named after this star whilst USS Azimech (AK-124)
USS Azimech (AK-124)
USS Azimech was a commissioned by the U.S. Navy for service in World War II, named after Azimech, the other name of Spica, the brightest star in constellation Virgo...

 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...

, a 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....

, was given the alternative name.