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==Arcturus in History==
Arcturus is well know known worldwide since [[antiquity]], thanks to the fact that it is one of the brightest stars in the night sky.
The star was seen known by ancient [[Polynesian]] navigators as '''Hōkūleʻa''', the "Star of Joy". The Polynesians knew the star was at its zenith over the [[Hawaii|Hawaiian islands]] and used this knowledge to sail from [[Tahiti]] and the Marquesas Islands to Hawaii. For their return trip, the Polynesians would use [[Sirius]], the zenith star of Tahiti. This trip has been duplicated several times using the same wayfinding technique of navigation through the use of these same stars since 1976 by the Polynesian Voyaging Society.
The star was known as ''Marpean-kurrk'' to the Koori of [[Australia]], its appearance signifying the birth of the larvae of the wood-ant in spring. The start of summer would be signaled by the star setting with the Sun. It was also seen as the mother of Antares (known to them as ''Djuit'').<ref>Mudrooroo (1994). Aboriginal mythology : an A-Z spanning the history of aboriginal mythology from the earliest legends to the present day. London: HarperCollins. p. 5. ISBN 1855383063.</ref>
==The Star==
[[Image:000Arcturus-star.jpg|thumb|right|200px|Comparison in size between Arcturus and the [[Sun]]. Copyright © Windows to the Universe [http://www.windows.ucar.edu/]. Used with permission.]]
Arcturus is an orange-red giant with of the spectral type K1.5 IIIpe. The star has some 24.5 times the diameter of our [[Sun]]. Like all giants, it has a low mass mass compared to its size, having only 1.5 times the mass of our Sun.<ref name="illinois">http://www.astro.illinois.edu/~jkaler/sow/arcturus.html</ref> Arcturus is 115 times as bright as our sun visually, although its absolute magnitude is 215 times as great counting the [[infrared]].<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002hgs..book.....K&db_key=AST&data_type=HTML&format=&high=45e3861c6616357</ref> The star has rather low [[metallicity]], with being only 17 to 32 percent as abundant as our Sun with in elements heavier then [[hydrogen]], based on its abundance of [[iron]].<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1998Obs...118..299G&data_type=PDF_HIGH&type=PRINTER</ref>
Arcturus is an older star, even possibly a [[metallicity|Population II]] star, forming in the thick disk that lies thousands of light years above and below the galactic plane. As Arcturus is more massive then our sun, it burned through its core fuel of [[hydrogen]] faster, likely exhausting it in five to eight billion years and evolving into a giant.<ref name="illinois">http://www.astro.illinois.edu/~jkaler/sow/arcturus.html</ref> Arcturus may have only recently entered this stage, its mass indicating the star hasn't suffered yet suffered from substantial loss of material after leaving the main sequence.<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1977ApJ...214..410A&data_type=PDF_HIGH&type=PRINTER</ref>
As a helium-burning giant star that has consumed all its [[hydrogen]] core fuel and left the main sequence, it has fully shifted to fusing [[helium]] in its core into [[carbon]] and [[oxygen]]. This stage of the star's life will only last some tens to hundreds of millions of years. Eventually the star will begin to loss lose its mass, and the gases will puff out as a[[ planetary nebula]] containing mostly hydrogen and helium, with smaller amounts of other elements. What will be left is a [[white dwarf]] star that will gradually cool and fade over time.
There are no known substellar companions orbiting Arcturus at this time. Any world that would have been [[terrestrial planet|Earth-like]] while Arcturus was on the main sequence would have long ago been destroyed. For such a world to exist now with liquid water on its surface, it would need to be centered around 11 AU away, or between the orbital distances of [[Saturn]] and [[Uranus]] in our solar system. Such a world would be extremely difficult to detect using current methods.
