Arcturus (; α Boo, α Boötis, Alpha Boötis ) is the brightest star in the constellation Boötes and in fact the northern celestial hemisphere.

Arcturus is the zenith star of the Hawaiian Islands.

According to the Hipparcos satellite, Arcturus is 36. 7 light years ( 11. 3 parsecs ) from Earth, relatively close in astronomical terms.

However, Alpha Centauri is a bright binary star, whose unresolved components to the naked eye are both fainter than Arcturus.

This makes Arcturus the third brightest individual star, just ahead of Alpha Centauri A ( α Cen A ), whose visual magnitude is − 0. 01.

Arcturus is visible from both hemispheres in the sky, as it is located less than 20 degrees north of the celestial equator.

From the northern hemisphere, an easy way to find Arcturus is to follow the arc of the handle of the Big Dipper.

Eta Bootis, or Muphrid, is only 3. 3 light years distant from Arcturus, and would have a visual magnitude-2½, whereas an observer on the former system would find Arcturus as bright as Venus as seen from Earth.

Arcturus is a type K1. 5 IIIpe orange giant star — the letters " pe " stand for " peculiar emission ," which indicates that the spectrum of light given off by the star is unusual and full of emission lines.

This is not too uncommon in red giants, but Arcturus has a particularly strong case of the phenomenon.

They suggested that the most plausible explanation for the variability of Arcturus is stellar oscillations.

In the case of Arcturus, this was an interesting discovery as it is known that the redder ( more towards or within the M spectral class ) a giant gets, the more variable it will be.

Extreme cases like Mira undergo large swings over hundreds of days ; Arcturus is not very red and is a borderline case between variability and stability with its short period and tiny range.

Arcturus has a much lower metallicity than our sun, and it is possibly a Population II star.

Arcturus is thought to be an old disk star, and appears to be moving with a group of 52 other such stars, known as the Arcturus stream.

Arcturus is likely to be around a billion years old, and has likely begun fusing helium into oxygen and carbon in its core.

Hipparcos also suggested that Arcturus is a binary star, with the companion about twenty times dimmer than the primary and orbiting close enough to be at the very limits of our current ability to make it out.

Arcturus is also included in the picture for size comparison.

Classical Latin Arcturus would also have become Art ( h ) ur when borrowed into Welsh, and its brightness and position in the sky led people to regard it as the " guardian of the bear " ( which is the meaning of the name in Ancient Greek ) and the " leader " of the other stars in Boötes.

The French mathematician and astronomer Jean-Baptiste Morin observed Arcturus in the daytime with a telescope ( a first for any star other than the sun ) in 1635, and has been seen at or just before sunset with the naked eye.

In practice, the traditional names are only universally used for the very brightest stars ( Sirius, Arcturus, Vega, etc.

* In David Lindsay's A Voyage to Arcturus there is a type of being called phaen, a third gender which is attracted neither to men nor women but to " Faceny " ( their name for Shaping or Crystalman, the Demiurge ).

His ship for this expedition was the Arcturus, a steam yacht considerably larger than the Noma that was capable of being at sea for extended periods of time.

The Arcturus was outfitted with Beebe's pulpit and boom walk from the Noma, as well as cages and tanks for live animals, chemicals and vials to preserve dead ones, and a darkroom for developing film and studying the bioluminescent animals they hoped to encounter.

Unauthorized adaptations of the game were published for the TI 99 / 4A ( as Arcturus ), Amstrad CPC ( as Zaxx ), BBC Micro ( as Fortress ), and the TRS-80 Color Computer ( as Zakssund ).

There are no " real " blue giants, stable stars of classification OxIII or BxIII ; instead, stars such as Bellatrix ( B2III ) are middle-aged massive stars which are in the process of becoming massive bright giants ( class II ), very much unlike red giant stars such as Arcturus ( K1III ) which represent the final stage of stellar evolution for lower mass stars and are stable as giants.

Arcturus is also home to a staggering array of oversized and often deadly megafauna, from the Arcturan Megaleech to the Arcturan Megavoidwhale, the Arcturan megagnat to the Arcturan megaelephant and megapuppy, as well as the megacamel, well known by the turn of phrase " one's soul moves at the speed of an Arcturan megacamel ", presumably the reason for distilling Arcturan Mega-gin.

David Lindsay's A Voyage to Arcturus, published in 1920 is one of the earliest examples of the type, although it differs from most of them in not assuming a science-fictional background of interplanetary or interstellar travel ; it is rather a philosophical romance, which uses an alien planet as a background for exploring philosophical themes.

Within the field of literature, he also worked with Colin Wilson and for a lavish Savoy Books edition of David Lindsay's A Voyage to Arcturus.

Finding a copy of Wells's Outline of History, it turns out to be identical to the one he knows until 1903, at which point the alternate Wells records the invention of anti-gravity, a fast human expansion into space, a brutal war for the conquest of Mars which Wells strongly denounces, followed by a titanic conflict with Arcturus.

It is at these shipyards that Jim Raynor's troops managed to commandeer a small fleet of combat vessels for his new rebel organisation after the fall of Tarsonis, even managing to hijack Arcturus Mengsk's flagship, the Hyperion, from the command of General Duke.

Hepesh must have made an agreement with Arcturus for Peladon's mineral deposits in exchange for his help, as Arcturus ' planet lacks minerals.

David Lindsay ( 3 March 1876 – 16 July 1945 ) was a Scottish author now best remembered for the philosophical science fiction novel A Voyage to Arcturus ( 1920 ).

162 Sonata No. 8 for Piano ( Arcturus ) ( 2005 )

The story begins sometime in the 29th century on the planet Wilson ( orbiting Arcturus ) with a young man named Giraut and his romantic, swashbuckling friends, who are all members of the Nou Occitan culture and residents in the Quartier de Jovents, a sort of playground for teens and twenty-somethings who have not yet moved on to the more " grown-up " lifestyle of their parents.

With an apparent brightness of 0. 03m, this is the second brightest star of the northern hemisphere ( after Arcturus ) and the fifth brightest star in all ; its spectral class is A0 V and it lies at a distance of only 25. 3 ly.

To demonstrate, Arcturus destroys a vase with an energy weapon mounted on its box.

The Spring Triangle is an astronomical asterism involving an imaginary triangle drawn upon the celestial sphere, with its defining vertices at Arcturus, Spica, and alternately Denebola or Regulus.

The proper motion of Gliese 710 is very small for its distance, meaning it is traveling nearly directly in our line of sight ; compare for example with Arcturus.

To the unaided eye, a more prominent star such as Sirius or Arcturus appears larger than a less prominent star such as Mizar, which in turn appears larger than a truly faint star such as Alcor.

A Voyage to Arcturus was published in 1920, but it was not a success, selling fewer than six hundred copies.

It is the brightest star in the constellation Auriga, the sixth brightest star in the night sky, the third brightest star in the northern celestial hemisphere ( after Arcturus and Vega ), and the fourth brightest star visible to the naked eye from the latitude 40 ° N. It is closer to the north celestial pole than any other first magnitude star ( Polaris is only second magnitude ).

And even among those Stars which are reckoned of the brightest Class, there appears a Variety of Magnitude ; for Sirius or Arcturus are each of them brighter than Aldebaran or the Bull's Eye, or even than the Star in Spica ; and yet all these Stars are reckoned among the Stars of the first Order: And there are some Stars of such an intermedial Order, that the Astronomers have differed in classing of them ; some putting the same Stars in one Class, others in another.

Using this logarithmic scale, it is possible for a star to be brighter than “ first class ”, so Arcturus is magnitude 0, and Sirius is magnitude − 1. 46.