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The Great Hyperbolic Omni-Cognate Neutron Wrangler, said Deep Thought, thoroughly rolling the Rs, could talk all four legs off an Arcturan1 MegaDonkey – but only I could persuade it to go for a walk afterwards.
– Douglas Adams' essential read The Hitchhiker's Guide to the Galaxy.
Boötes the Constellation
|Area:||907 sq deg|
|Co-ordinates2:||Right Ascension 15h, Declination +30°|
Boötes (pronounced boh-oh-teez) the Herdsman3 is one of Ptolemy's 48 original constellations, so it is classified 'ancient'. Following the 'arc' of the handle of the Big Dipper (going away from the bowl) you will land right on Arcturus (alpha Boötis). Therefore, 'arc to Arcturus' the saying goes - followed by 'spike to Spica', because straight 'down' from Arcturus you will land on Spica in Virgo.
Boötes is kite-shaped and shares borders with (clockwise from the north) Draco, Ursa Major, Canes Venatici, Coma Berenices, Virgo, Serpens Caput, Corona Borealis and Hercules. Surprisingly for such a large area (it is the 13th-largest constellation) there are no Messier objects. Interestingly, there is a rather huge mysterious 'nothing' (absence of galaxies) called the Boötes Void.
This 'supervoid' was discovered in 1981. It is more than a billion light years4 from us and measures almost 350 million light years in diameter. There are many theories about the Boötes Void; it remains an enigmatic mystery and popular science fiction topic.
According to the Greek myth, the great god Zeus had a dalliance with Callisto, the daughter of King Lycaon of Arcadia; and she bore a son who she named Arcas. King Lycaon did not believe his daughter when she claimed the child's father was Zeus, so invited Zeus to join them for a meal. The meat offered to Zeus was unusual - it was in fact the sliced and diced flesh of the infant Arcas, who had been killed earlier on the instructions of the goddess Hera, Zeus' jealous wife.
Zeus did not relish having his son served up on a silver platter and took his revenge on King Lycaon by killing his sons. He then gathered up the body parts of Arcas and put him back together, before handing the child over to Atlas' daughter Maia5 to raise.
To keep Callisto safe from Hera, Zeus turned Callisto into a bear. When Arcas grew up he was out hunting one day when the bear rushed to embrace him. Thinking he was being attacked, Arcas determined to kill the bear, not knowing it was really his mother. Callisto raced to the Temple of Zeus to appeal on their behalf and Zeus placed them both in the heavens: Callisto as Ursa Major and Arcas as the constellation Boötes the Herdsman.
Another version of the tale has a slightly different ending: the mother and son are transformed into Ursa Major and Ursa Minor. In this version, Boötes honours the herdsman who invented the plough. This so delighted Ceres, the goddess of agriculture, that she arranged his reward with Zeus: his own constellation, rotating the heavens for eternity.
The scientific star names are simple to understand (if you know your Greek alphabet). For example, 'alpha Boötis' means it is the brightest star in the constellation Boötes. The next brightest is designated 'beta' etc. This is known as the 'Bayer designation'. Some stars have proper names as well, for example, alpha Boötis is Arcturus. Others are known by their catalogue number.
Arcturus is a first magnitude orange giant at just 36 light years distant. It is one of the brightest stars in the northern hemisphere of the celestial globe and the fourth-brightest star in the sky overall. Arcturus means 'bear guardian' in Greek; it was known by Homer, Hesiod and Ptolemy. In this fabulous Astronomy Picture of the Day image, Arcturus is in the centre of the picture between Jupiter and 'The Plough' asterism (part of the constellation Ursa Major).
|α Boo||alpha Boo||Arcturus||-0.04||36||Orange giant|
|β Boo||beta Boo||Nekkar||+3.4||220||Yellow giant|
|γ Boo||gamma Boo||Seginus||+3||86||White giant|
|δ Boo||delta Boo||49 Boötis||+3.4||120||Binary star system|
|ε Boo||epsilon Boo||Pulcherrima||+2.7 var||210||Binary star system|
|ζ Boo||zeta Boo||30 Boötis||+3.7||200||Binary star system|
|η Boo||eta Boo||Muphrid||+2.7||40||Binary star system|
|θ Boo||theta Boo||Asellus Primus||+4 var||48||Yellow-white dwarf|
|ι Boo||iota Boo||Asellus Secundus||+4.7 var||98||Binary star system|
|κ Boo||kappa Boo||Asellus Tertius||+4.5 var||160||Binary star system|
|λ Boo||lambda Boo||19 Boötis||+4.8 var||97||White dwarf|
|μ Boo||mu Boo||Alkalurops||+4.9 var||123||Triple star system|
|ν Boo||nu Boo||52 Boötis||+5 var||900||Binary star system|
|ξ Boo||xi Boo||37 Boötis||+4.7 var||22||Binary star system|
|ο Boo||omicron Boo||35 Boötis||+4.7||230||Orange giant|
|π Boo||pi Boo||29 Boötis||+5 var||320||Binary star system|
|ρ Boo||rho Boo||Hemelein Prima||+3.7 var||150||Orange giant|
|σ Boo||sigma Boo||Hemelein Secunda||+4.4 var||50||Yellow-white dwarf|
|τ Boo||tau Boo||4 Boötis||+4.5 var||51||Binary star system|
|υ Boo||upsilon Boo||5 Boötis||+4 var||230||Orange giant|
|φ Boo||phi Boo||54 Boötis||+5.2 var||158||Yellow giant|
|χ Boo||chi Boo||48 Boötis||+5.3 var||220||White dwarf|
|ψ Boo||psi Boo||43 Boötis||+4.5 var||250||Orange giant|
|ω Boo||omega Boo||41 Boötis||+4.8 var||368||Orange giant|
New General Catalogue (NGC)
The NGC was compiled by John Louis Emil Dreyer (director of the Armagh Observatory from 1882 - 1916). NGC 5548 is a Seyfert galaxy. These types of galaxy, identified in 1943 and named after their discoverer Carl Keenan Seyfert, have an intensely bright, compact and highly active nucleus, caused by a supermassive black hole at their core.
NGC 5466 is the only globular cluster in Boötes. It was discovered by William Herschel in May 1784, who catalogued it H VI.9.
|NGC 5466||Globular cluster||+9.04||51,800|
|NGC 5248||CW spiral galaxy||+10.9||75m7|
|NGC 5523||Edge-on spiral galaxy||+13.4||99m|
|NGC 5529||Edge-on spiral galaxy||+12.9||112m|
|NGC 5533||ACW spiral galaxy||+11.8||110m|
|NGC 5548||Seyfert spiral galaxy||+13.1||220m|
|NGC 5557||Elliptical galaxy||+11.1||105m|
|NGC 5653||CW spiral galaxy||+12.7||125m|
|NGC 5669||Barred CW spiral galaxy||+13.2||50m|
|NGC 5676||ACW spiral galaxy||+11.1||77m|
|NGC 5689||Barred edge-on spiral galaxy||+11.9||85m|
|NGC 5714||Edge-on spiral galaxy||+14.2||82m|
|NGC 5859||Barred ACW spiral galaxy||+13.1||136m|
|NGC 5899||Barred ACW spiral galaxy||+11.8||78m|
Meteor showers are particles of dust hitting the Earth's atmosphere. All the meteors in a shower are travelling in the same direction in space, so they appear to spread out from a single point in the sky known as the radiant. The meteor shower is normally named after the constellation which contains the radiant. If there's more than one meteor shower per constellation, then each shower is named after the closest star. The January Quadrantid meteor shower is an exception; although its radiant is in Boötes, it is named after the now defunct constellation, the Quadrant. It hails from a piece of a comet which disintegrated over half a millennium ago, in 14908. The remainder of the comet is now a near-Earth asteroid called 2003 EH1.
The Earth passes through the debris field at such an angle that the shower is extremely short (just a few hours). But it is a good show if you catch one; the ZHR (Zenithal Hourly Rate) is over 100 per hour.
Extrasolar Planets in Boötes
Several extrasolar planetary systems have been found in the constellation Boötes; the first was discovered in 1997. One star system has two planets.
The nomenclature that has been decided upon for planets is to use a lower-case letter after the parent star catalogue number (or name) eg, 'Tau Boötis A b'. This stays with the planet regardless of whether further discoveries are subsequently made within the same solar system, and despite the position of the new planet relative to the star. Therefore, the first-discovered planet of HD 128311 is HD 128311 b, and HD 128311 c was detected later.
The planet HD 128311 b is in the system's 'Goldilocks zone' (habitable zone), but as a gas giant is not a candidate in the search for extra-terrestrial life. However, should the planet have a rocky moon with enough gravity to retain an atmosphere, that would make it a distinct possibility.
The figures given in the table below are the length of the planet's orbital period around its parent star, which we know of as a year. The mass of the extrasolar planet is compared with that of Jupiter, our solar system's largest planet, known to astronomers as the 'Jovian scale'.
Extrasolar Planets Table
|Star name or
|Year of discovery||Comments|
|Tau Boötis A||Tau Boötis A b||7||3.3||1997||Hot superjovian|
|HAT-P-4||HAT-P-4 b||0.7||3.06||2007||Gas giant|
|HD 132406||HD 132406 b||5.6||1,000||2007||Superjovian|
|HD 128311||HD 128311 b||2.2||460||2002||Gas giant|
|HD 128311||HD 128311 c||3.2||920||2005||Gas giant|
|WASP-14||WASP-14 b||7.3||2.2||2008||Hot superjovian|
|HD 136418||HD 136418 b||2||464.3||2010||Gas giant|
SCP 06F6 was discovered on 21 February, 2006, by the Hubble Space Telescope, where nothing had been on 29 January. This means it brightened by a factor of over 200. Thought originally to be a supernova, it kept growing brighter for too long, around 100 days. Normal supernovae reach peak brightness between 20 and 30 days after the explosion then begin to fade. One explanation of the 100-day brightness is distance, but a 100-day stretched-event would mean the object is approximately 12 billion light years away, and the explosion was too bright for this distance to be possible. Besides, its colour did not change from when it was first observed to when it faded; normally, temperature change after an explosion would register different colours. Despite extensive studies, astrophysicists cannot match up its spectral lines with any known elements. As astronomers cannot match the object to any known class of celestial object, therefore (for the time being) it represents a new class. Speculations abound, including 'the explosion of a carbon star' and 'the collision of a white dwarf with a black hole'.
It's a very intriguing object
– Supernova researcher Stefan Immler of NASA Goddard Space Flight Center, Maryland, US.
Down to Earth
While this article is primarily about the constellation Boötes, the author thought you might like to see some of the other instances where Boötes has appeared.
Boötes in Modern Culture
The Boötes Void is mentioned in Night Train by Martin Amis, Time Master by Robert Lull Forward (1932 - 2003) and Accelerando by Charlie Stross.
Ix is the ninth planet orbiting mu Boötis (Alkalurops) in the Dune universe of Frank Herbert.
Arcturus (alpha Boötis) is also popular with science fiction writers, especially Douglas Adams, who used a variety of Arcturan fauna such as the Arcturan MegavoidWhale, and mentioned distilling Arcturan Mega-gin, in his Hitchhiker novels.