Spica (α Vir / α Virginis /
AlphaAlpha 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 letter Aleph...
Virginis) is the brightest star in the
constellationIn modern astronomy, a constellation is an area of the celestial sphere, defined by exact boundaries.The term "constellation" can also be used loosely to refer to just the more prominent visible stars that seem to form a pattern in that area.-Definitions:...
VirgoVirgo 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
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
. A
blue giantIn space sciences, a blue giant is a star with a spectral type of O or B and a luminosity class of III...
, it is a
variableA star is classified as variable if its apparent brightness 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 typeBeta 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
HipparchusHipparchus, 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
precessionPrecession refers to a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...
of the
equinoxAn equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the Sun being vertically above a point on the Equator...
es.
Spica (α Vir / α Virginis /
AlphaAlpha 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 letter Aleph...
Virginis) is the brightest star in the
constellationIn modern astronomy, a constellation is an area of the celestial sphere, defined by exact boundaries.The term "constellation" can also be used loosely to refer to just the more prominent visible stars that seem to form a pattern in that area.-Definitions:...
VirgoVirgo 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
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
. A
blue giantIn space sciences, a blue giant is a star with a spectral type of O or B and a luminosity class of III...
, it is a
variableA star is classified as variable if its apparent brightness 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 typeBeta 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
HipparchusHipparchus, 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
precessionPrecession refers to a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...
of the
equinoxAn equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the Sun being vertically above a point on the Equator...
es. A
templeA 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
HathorHathor , , was an Ancient Egyptian goddess who personified the principles of feminine love, motherhood and joy. She was one of the most important and popular deities throughout the history of Ancient Egypt...
) at
ThebesThebes 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 . It was inhabited beginning in around 3200 BC. It was the eponymous 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.
Nicolaus CopernicusNicolaus Copernicus was the first astronomer 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
triquetrumframe|Drawing of a triquetrum by Wilhelm Schickard, Basel University LibraryThe 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 magnitudeThe apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the atmosphere...
varies between +0.92 and +1.04, with a
periodThe orbital period 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.There are several kinds of...
of 4.0142 days. This slight dip in magnitude is barely noticeable visually. It is also a
variableA star is classified as variable if its apparent brightness 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 typeBeta 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 has a luminosity about 2,300 times that of the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
. Spica is a double star, but the distance between the two stars is so small that it distorts the image, and makes the two stars seem like one, with very slight brightness variations.
Visibility
Located close to the
eclipticThe ecliptic is the apparent path that the Sun traces out in the sky during the year, appearing to move eastwards on an imaginary spherical surface, the celestial sphere, relative to the fixed stars. More accurately, it is the intersection of the celestial sphere with the ecliptic plane, which is...
, Spica can be
occultedAn 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
MoonThe Moon is Earth's only natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is , about thirty times the diameter of the Earth. The common centre of mass of the system is located at about —a quarter the Earth's...
and sometimes by the
planetA 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
VenusVenus is the second-closest planet to 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...
passed in front of the star (as seen from
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
) on November 10, 1783. The next occultation will occur September 2, 2197, when Venus again passes in front of Spica. The Sun passes a little more than 2º north of Spica around October 16 every year, and the star's
heliacal risingThe heliacal rising of a star occurs when it first becomes visible above the eastern horizon at dawn, after a period when it was hidden below the horizon or when it was just above the horizon but hidden by the brightness of the sun.Each day after the heliacal rising, the star will appear to rise...
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 will pass 3.5
o north of the star on November 3.
http://www.poyntsource.com/New/Diary.htm
An easy way to find Spica is to follow the arc of the handle of the
Big DipperThe Plough or the Big Dipper is an asterism of seven stars that has been recognized as a distinct grouping in many cultures from time immemorial. The comprising stars are the seven brightest of the formal constellation Ursa Major.-Europe:...
to
Arcturus|- bgcolor="#FFFAFA"| note : || H and K emission vary.Arcturus is the brightest star in the constellation Boötes. With a visual magnitude of −0.05, it is also the third brightest star 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
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
spīca virginis "Virgo's ear of grain" (usually
wheatWheat is a worldwide cultivated grass from the Fertile Crescent region of the Near East. 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 XiuThe 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 constellationChinese constellations are the way ancient Chinese grouped the stars. They are very different from the modern IAU recognized constellations. This is due to the independent development of ancient Chinese astronomy....
s. In
HinduA Hindu is an adherent of Hinduism, a set of religious, philosophical and cultural systems that originated in the Indian subcontinent. The vast body of Hindu scriptures, divided into Śruti and Smriti , lay the foundation of Hindu beliefs which primarily include dhárma, kárma, ahimsa and saṃsāra...
astronomyThe 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
NakshatraNakshatra or lunar mansion is one of the 27 divisions of the sky, identified by the prominent star in them, used in Jyotisha.-Overview:...
Chitra. 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'.
In medieval
astrologyAstrology is a group of systems, traditions, and beliefs which hold that the relative positions of celestial bodies and related details can provide information about personality, human affairs, and other terrestrial matters. A practitioner of astrology is called an astrologer...
, it was a Behenian fixed star, associated with the
emeraldEmeralds 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. Most emeralds are highly included, so their toughness is classified as generally poor...
and
sageSalvia officinalis is a small perennial evergreen subshrub, with woody stems, grayish leaves, and blue to purplish flowers. It is a member of the mint family, Lamiaceae...
. In his
De Occulta PhilosophiaDe occulta philosophia libri tres is Heinrich Cornelius Agrippa's study of occult philosophy, acknowledged as a significant contribution to the Renaissance philosophical discussion concerning the powers of ritual magic and its relationship with religion.The three books deal with Elemental,...
, Cornelius Agrippa attributes its kabbalistic symbol
to
Hermes TrismegistusHermes Trismegistus is the representation of the combination of the Greek god Hermes and the Egyptian god Thoth. In Hellenistic Egypt, the Greeks recognised the congruence of their God Hermes with the Egyptian god Thoth...
.
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 IcePushing 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 ReynoldsAlastair 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
mangaManga consist of comics and print cartoons , in the Japanese language and conforming to the style developed in Japan in the late 20th century...
and series
Twin Spicais a Japanese science fiction manga series by Kō Yaginuma. It was serialized in the seinen magazine Comic Flapper between September 2001 and August 2009. 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.
External links