Crux

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Crux

Constellation
List of stars in Crux
Abbreviation	Cru
Genitive	Crucis
Pronunciation	/ˈkrʌks/, genitive /ˈkruːsɨs/
Symbolism	Southern Cross
Right ascension	12.5
Declination	−60
Area	68 sq. deg. (88th)
Main stars	4
Bayer/Flamsteed stars	19
Stars with known planets	1
Bright stars	4
Nearby stars	0
Brightest star	Acrux (α Cru) (0.87m)
Nearest star	η Cru (64.2 ly)
Messier objects	0
Meteor showers	Crucids
Bordering constellations	Centaurus Musca
Visible at latitudes between +20° and −90°. Best visible at 21:00 (9 p.m.) during the month of May.

Crux is the smallest of the 88 modern constellations, but is one of the most distinctive. Its name is Latin for cross, and it is dominated by a cross-shaped asterism that is commonly known as the Southern Cross because throughout this Common Era it has been easily visible from the southern hemisphere, at practically any time of year, although it is also visible near the horizon from tropical latitudes of the northern hemisphere, for a few hours every night, during the spring months; for instance, from Cancun -- or any other place al latitude 25º N or less, with unobstructed view to the South—at around 10 pm, at the end of April.

Crux is bordered by the constellations Centaurus, which surrounds it on three sides, and Musca.

[edit] Location and identification

The five brightest stars in Crux are clearly visible in this picture. The red giant Gacrux and orange giant Juxta Crucem are distinctly different from the three other major stars of the constellation, which are Blue-white in colour

Contrary to popular belief, Crux is not opposite to Ursa Major. In fact, in tropical regions both Crux (low in the south) and Ursa Major (low in the north) can be seen in the sky from April to June. Crux is exactly opposite to Cassiopeia on the celestial sphere, and therefore it cannot be in the sky with the latter at the same time. For locations south of 34°S, Crux is circumpolar and thus always visible in the night sky.

Crux is sometimes confused with the nearby False Cross by stargazers. Crux is somewhat kite-shaped, and it has a fifth star (ε Crucis). Crux may also resemble the shape of an inverted U.S. space shuttle, as if flying upside down through the sky. The False Cross is diamond-shaped, somewhat dimmer on average, does not have a fifth star and lacks two "Pointer Stars".

[edit] Notable features

[edit] Stars

A CTX image of crux.

Three of the five main Crux stars—–Acrux, Mimosa, and Delta Crucis—–are co-moving B-type members of the Scorpius-Centaurus Association, the nearest OB association to the Sun^[1]. They are among the highest-mass stellar members of the Lower Centaurus-Crux subgroup of the association, with ages of roughly 10 to 20 million years^[2][3].

[edit] Markers

Since the southern sky lacks an easily visible pole star, Alpha and Gamma (known as Acrux and Gacrux respectively) are commonly used to mark south. Following the line defined by the two stars for approximately 4.5 times the distance between them leads to a point close to the Southern Celestial Pole.

Alternatively, if a line is constructed perpendicularly between Alpha Centauri and Beta Centauri, the point where the above line and this line intersect marks the Southern Celestial Pole. The two stars are often referred to as the "Pointer Stars" or "White Pointers", allowing people to easily find the top of Crux

[edit] Named stars

• α is named Acrux, a concatenation of "Alpha" and "Crux"
• β is named Becrux a concatenation of "Beta" and "Crux" and is also named after the Mimosa plant
• γ is named Gacrux, a concatenation of "Gamma" and "Crux"

[edit] Deep sky objects

The Coalsack Nebula is the most prominent dark nebula in the skies, easily visible to the naked eye as a big dark patch in the southern Milky Way.

Another deep sky object within Crux is the Open Cluster NGC 4755, better known as the Jewel Box or Kappa Crucis Cluster, that was discovered by Nicolas Louis de Lacaille in 1751-1752. It lies at a distance of about 7,500 light years and consists of approximately 100 stars spread across an area of about 20 light-years square.

[edit] History

Crux was visible to the Ancient Greeks, who regarded it as part of the constellation Centaurus. At the latitude of Athens in 1000 BC, Crux was clearly visible, though low in the sky. However, the precession of the equinoxes gradually lowered its stars below the European horizon, and they were eventually forgotten by the inhabitants of northern latitudes. By AD 400, most of the constellation never rose above the horizon for Athenians.

Crux was rediscovered by Europeans during the Age of Discovery. Amerigo Vespucci mapped Alpha Centauri and Beta Centauri as well as the stars of modern Crux on his expedition to South America in 1501.

The separation of Crux from Centaurus is generally attributed to the French astronomer Augustin Royer in 1679. Other historians attribute the invention of Crux to Petrus Plancius in 1613, noting that the constellation was later published by Jakob Bartsch in 1624.^{[citation needed]}

[edit] Cultural significance

As a highly distinctive asterism, Crux has great significance in the cultures of the southern hemisphere.

In Australian Aboriginal astronomy, Crux and the Coalsack, mark the head of the 'Emu in the Sky' in several Aboriginal cultures, while Crux itself is said to be a possum sitting in a tree.

A stone image of the constellation has been found at the archaeological site of Machu Picchu, Peru.^{[citation needed]} In Mapudungun, the language of Patagonian Mapuches, the name of Crux is Melipal, which means "four stars". In Quechua, the language of the Inca civilization, Crux is known as "Chakana", which means literally "stair" (chaka, bridge, link; hanan, high, above), but carries a deep symbolism within Quechua mysticism.^[4].

The Māori name for Crux is "Te Punga" - "the anchor". It is thought of as the anchor of Tama-rereti's waka (the Milky Way), where the Pointers are its rope. In Tonga it is known as Toloa — duck; it is a duck flying over, heading south, and one of his wings (δ) is wounded because Ongo tangata — 2 men — α and Β Centauri threw a stone at it. The Coalsack is known as Humu — triggerfish, because of its shape.^[5]

In Indonesia and Malaysia, it is known as Buruj Pari (The Stingray). In ancient Hindu astrology, the modern Crux is referred to as "Trishanku".

Among Tuaregs, the 4 most visible stars of Crux are considered iggaren, i.e. four Maerua crassifolia trees.

Southern Cross is also a song by the classic rock group Crosby, Stills and Nash, written by Rick Curtis, Michael Curtis, and Stephen Stills.

[edit] Flags and symbols that incorporate Crux

Beginning in the colonial age, Crux became used as a national symbol by several southern nations. The brightest stars of Crux appear on the flags of Australia, Brazil, New Zealand, Papua New Guinea, and Samoa. They also appear on the Australian States and Territories of Victoria, the Australian Capital Territory, the Northern Territory, as well as the flag of Magallanes Region of Chile, and several Argentine provincial flags and emblems (e.g., Tierra del Fuego and Santa Cruz). The flag of the Mercosur trading zone displays the four brightest stars. Crux also appears on the Brazilian coat of arms.

Crux, appearing on a number of flags and insignia.

In 1893, Australian poet Banjo Paterson wrote:

The English flag may flutter and wave,
where the world wide oceans toss,
but the flag the Australian dies to save,
is the flag of the Southern Cross.

The five stars are also in the logo of an Brazilian soccer team called Cruzeiro Esporte Clube. A stylized version of Crux appears on the Eureka Flag. The constellation was also used on the dark blue, shield-like patch worn by personnel of the U.S. Army's Americal Division, which was organized in the Southern Hemisphere, on the island of New Caledonia, and also the blue diamond of the U.S. 1st Marine Division, which fought on the Southern Hemisphere islands of Guadalcanal and New Britain.

•  Australia
•  Brazil
•  New Zealand
•  Niue
•  Papua New Guinea
•  Samoa
•  Tokelau

[edit] References

[edit] External links

Wikimedia Commons has media related to: Crux

• Letter of Andrea Corsali 1516-1989: with additional material ("the first description and illustration of the Southern Cross, with speculations about Australia ...") digitised by the National Library of Australia.
• The Deep Photographic Guide to the Constellations: Crux.
• The Cambridge Guide to the Constellations, Michael E. Bakich, Cambridge University Press, 1995, pg. 85.
• Universe: The Definitive Visual Dictionary, Robert Dinwiddie et al., DK Adult Publishing, (2005), pg. 396.
• The Sign of the Southern Cross Black Sabbath
• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.
• Southern Cross Starry Night Photography.
• Star Tales – Crux
• Finding the South Pole in the sky
• Southern Cross in Te Ara - the Encyclopedia of New Zealand

Coordinates: 12^h 30^m 00^s, −60° 00′ 00″