Spica

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Spica

Spica (also known as a Vir / a Virginis / Alpha

Alpha (letter)

Alpha is the first letter of the Greek alphabet. In the system of Greek numerals it has a value of 1. It was derived from the Phoenician alphabet Aleph ....
Virginis) is the brightest star in the constellation

Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
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

List of brightest stars

Bright stars are bright because they have high luminosity and/or they are nearby. Below are the 91 brightest individual stars as seen from Earth in visible wavelengths ....
in the nighttime sky. It is 260 light years distant from Earth

Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
. 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 . In the standard Hertzsprung-Russell diagram, blue giants are found in the upper left corner, due to their high luminosity and early spectral type....
, 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....
.

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...
with the data which enabled him to discover precession

Precession

Precession refers to a change in the direction of the axis of a rotation object. In physics, there are two types of precession, torque-free and torque-induced, the latter being discussed here in more detail....
of the equinox

Equinox

Equinoxes occur twice a year, when the tilt of the Earth's axis is inclined neither away from nor toward the Sun, causing the Sun to be located vertically above a point on the equator....
es. 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....
to Menat (an early Hathor

Hathor

In Egyptian mythology, Hathor was originally a personification of the Milky Way, which was seen as the milk that flowed from the udders of a heavenly cow....
) at Thebes

Thebes, Egypt

Thebes was a city in Ancient Egypt located about 800 km south of the Mediterranean, on the east bank of the river Nile . It was the capital of Waset, the fourth Upper Egyptian Nome ....
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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Observation history

Spica is believed to be the star that provided Hipparchus

Hipparchus

Precession

Equinox

Temple

Hathor

In Egyptian mythology, Hathor was originally a personification of the Milky Way, which was seen as the milk that flowed from the udders of a heavenly cow....
) at Thebes

Thebes, Egypt

Nicolaus Copernicus

Nicolaus Copernicus was the first astronomer to formulate a scientifically-based heliocentrism cosmology that 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.

Characteristics

Spica is the brightest of the rotating ellipsoidal variables. Its apparent magnitude

Apparent magnitude

The apparent magnitude of a celestial body is a measurement of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the Earth's atmosphere....
varies between +0.92 and +1.04, with a period

Orbital period

The orbital Periodicity is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars....
of 4.0142 days. This slight dip in magnitude is barely noticeable visually. It is also a variable

Variable star

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....
. Spica has a luminosity about 2,300 times that of the Sun

Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
.

Visibility

Located close to the ecliptic

Ecliptic

The ecliptic is the apparent path that the Sun traces out in the sky during the year. As it appears to move in the sky in relation to the stars, the apparent path aligns with the planets throughout the course of the year....
, 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 and can also be used in a general sense to describe when an object in the foreground occults objects in the background....
by the Moon

Moon

The Moon is Earth's only natural satellite and the List of natural satellites by diameter satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is km, about thirty times the diameter of the Earth....
and sometimes by the planet

Planet

A planet , as 2006 definition of planet by the International Astronomical Union , is a celestial body orbiting a star or Stellar evolution#Stellar remnants that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared the neighbourhood of planetesimals....
s. The last planetary occultation of Spica occurred when Venus

Venus

Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus , the Roman mythology goddess of love....
passed in front of the star (as seen from Earth

Earth

Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
passes a little more than 2º north of Spica around October 16 every year.

An easy way to find Spica is to follow the arc of the handle of the Big Dipper

Big Dipper

The seven brightest stars of the constellation Ursa Major, the Great Bear, form a well-known asterism that has been recognized as a distinct grouping in many cultures from time immemorial....
to Arcturus

Arcturus

|- bgcolor="#FFFAFA"| note : || H and K emission vary.Arcturus is the brightest star in the constellation Bo?tes. With a visual magnitude of -0.05, it is also the list of brightest stars in the night sky, after Sirius and Canopus ....
, and then continue on the same distance to Spica ("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, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
spica virginis "Virgo's ear of grain" (usually wheat

Wheat

Wheat , is a worldwide cultivated Poaceae from the Levant region of the Middle East. Globally, after maize, wheat is the second most-produced food among the cereal just above rice....
). In Chinese astronomy, the star is known as Jiao Xiu 1 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 ....
, one of the Chinese constellation

Chinese constellation

Chinese constellations are the way ancient Chinese grouped the stars. They are very different from the modern International Astronomical Union recognized constellations....
s. In Hindu 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....
, Spica corresponds to the Nakshatra

Nakshatra

A nakshatra or lunar mansion is one of the 27 or 28 divisions of the sky, identified by the prominent star in them, that the Moon passes through during its monthly cycle, as used in Hindu astronomy and Jyotisha....
Chitra.

Medieval names include Azimech, from Arabic as-simak al-a'zal "the Undefended", and Alarph, Arabic for "the Grape Gatherer".

In medieval astrology

Astrology

Astrology is a group of systems, traditions, and beliefs which hold that the relative positions of astronomical object and related details can provide useful information about personality, human affairs, and other terrestrial matters....
, it was a Behenian fixed star, associated with the emerald

Emerald

Emeralds are 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

Sage

Sage or SAGE may refer to one of the following:...
. In his De Occulta Philosophia

Libri tres de occulta philosophia

De occulta philosophia libri tres is Heinrich Cornelius Agrippa's study of occult philosophy, acknowledged as a significant contribution to the Renaissance philosophy discussion concerning the powers of ritual magic and its relationship with religion....
, Cornelius Agrippa attributes its kabbalistic symbol

to Hermes Trismegistus

Hermes Trismegistus

Hermes Trismegistus is the representation of the combination of the Greek mythology god Hermes and the Egyptian god Thoth. In Hellenistic Egypt, the Greeks recognised the congruence of their God Hermes with the Egyptian god Thoth....
.

Spica was used in the novel Pushing Ice
Pushing Ice

Pushing Ice is a 2005 science fiction novel by Wales author Alastair Reynolds. According to Reynolds' Web site, the story takes place in a universe separate and distinct from his Revelation Space universe....
by Alastair Reynolds

Alastair Reynolds

Alastair Preston Reynolds is a Wales 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 University, where he read Physics and Astronomy....
as the distant star to which the protagonists are carried by alien technology

The Japanese manga

Manga

, , are comics and print cartoons , in the Japanese language and conforming to the style developed in Japan in the late 20th century. In their modern form, manga date from shortly after World War II, but they have a long, complex pre-history in earlier Japanese art....
and series Twin Spica

Twin Spica

is a Japanese science fiction manga series by Ko Yaginuma. It began serialization in the seinen magazine Comic Flapper in January 2001. Twin Spica tells the story of a group of Japanese high school students training to become astronauts....
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.

Spica

Observation history

Characteristics

Visibility

Etymology and cultural significance

External links