The Great Hyperbolic Omni-Cognate Neutron Wrangler, said Deep Thought, thoroughly rolling the r's, 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

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'll land on Spica in Virgo.

Boötes is kite-shaped and shares borders with (clockwise from north) Draco, Ursa Major, Canes Venatici, Coma Berenices, Virgo, Serpens Caput, Corona Borealis and Hercules. Surprisingly for such a large area (it's 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's over a billion light years from us and it measures almost 350 million light years in diameter. There are many theories about the Boötes Void but it remains an enigmatic mystery and a popular science fiction topic.

Mythology

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 whom she named Arcas. King Lycaon did not believe his daughter when she claimed that the child's father was Zeus, so he invited Zeus to join them for a meal. The meat Zeus was offered 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. Then he gathered up the body parts of Arcas and put him back together before handing the child over to Atlas' daughter Maia⁴ to raise. To keep Callisto safe from Hera, Zeus turned her 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 tells the same story but in a slightly different ending, the mother and son were transformed into Ursa Major and Ursa Minor. With that 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.

Stars

The scientific star names are simple to understand (if you know your Greek alphabet). For example: 'alpha Boötis' means that it is the brightest star in the constellation Boötes. The next brightest is designated 'beta', etc. Some stars have proper names as well; for example, alpha Boötis is Arcturus; others are known by their catalogue numbers or 'Bayer designation'.

Arcturus is a first magnitude orange giant at just 36 light years distant. It is the brightest star 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).

New General Catalogue (NGC)

The NGC catalogue was compiled by John Louis Emil Dreyer (the director of the Armagh Observatory from 1882 to 1916).

NGC 5548 is a Seyfert galaxy. This type 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.

There are many galaxies viewable in the direction of Boötes⁵, including the stunning edge-on spirals NGC 5529 and NGC 5689.

Meteor Showers

Meteor showers are particles of dust hitting the Earth's atmosphere, usually originating from a certain point in the sky known as the radiant. The meteor shower is generally named after the nearest star to the radiant. The January Quadrantid meteor shower doesn't follow the usual rules, it hails from a piece of a comet which disintegrated over half a millennia ago in 1490⁷. The remainder of the comet is now a near-Earth asteroid which is called 2003 EH1.

The closest constellation the Quadrantids appear to originate from is Boötes, and the Earth passes through the debris field at such an angle that the shower is extremely short (just a few hours), but it's a good show if you catch one, the ZHR (Zenithal Hourly Rate) is over 100 per hour.

In the early hours of 4 January, 2008, the Quadrantid meteor shower was viewed from the air and the image also captured a gorgeous green   aurora.

Extrasolar Planets in Boötes

There have been four extrasolar planetary systems found in the constellation Boötes up to 2007; the first was discovered in 1997 and 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 Ab'. This stays with the planet no matter if subsequently more discoveries are 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 it's not a candidate for 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.

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 size of the extrasolar planet is compared to the mass of Jupiter, our Solar System's largest planet, known by astronomers as the 'Jovian scale'.

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.
  

• Fleet Captain Garth⁸ of Izar (another name for Pulcherrima, epsilon Boötis) was a character in the Star Trek TOS episode 'Whom Gods Destroy'.
  

• Ix is the 9th 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.