49 Fun Facts About Constellations

How many constellations does the International Astronomical Union officially recognise?

By 1930 the whole sky had been carved into 88 tidy regions so that every star belongs to exactly one of them.

Which constellation is the largest of all, sprawling across roughly 1,303 square degrees of sky?

Hydra, the water snake, covers 1,303 square degrees and stretches more than 100 degrees across the sky, yet has only one reasonably bright star, Alphard, 'the solitary one'.

Which constellation is the smallest of the 88 by area?

Crux, the Southern Cross, covers just 68 square degrees; the ancient Greeks counted its stars as part of Centaurus before precession carried them below Europe's horizon.

How many constellations did Ptolemy list in the Almagest in the 2nd century AD, 12 of them the zodiac?

48: the 12 of the zodiac, 21 to the north and 15 to the south; all but one survive today, the exception being a giant ship carved up in the 18th century.

Which of Ptolemy's 48 constellations was later broken up into Carina, Puppis and Vela?

Argo Navis, the Argonauts' ship, is the only Ptolemaic constellation no longer recognised; Lacaille split it in 1752 into Carina (keel), Puppis (stern) and Vela (sails), and its brightest star Canopus now belongs to Carina.

Which French astronomer introduced 14 southern constellations named mostly after scientific instruments in the 1750s?

Nicolas-Louis de Lacaille, observing from the Cape of Good Hope in 1751-52, added Antlia the air pump, Fornax the furnace, Microscopium, Telescopium and Horologium the clock, and catalogued nearly 10,000 southern stars.

Which feature on Earth is the only one to have a constellation named after it?

Table Mountain, overlooking Cape Town where Lacaille observed in 1751-52, gave its Latin name to Mensa, the faintest constellation, whose brightest star is only magnitude 5.1.

Whose 1603 atlas Uranometria, the first to cover the whole celestial sphere, introduced Greek-letter star labels?

Johann Bayer, an Augsburg lawyer, published Uranometria in 1603 with stars lettered roughly by brightness, Alpha through Omega; it also imported the new southern constellations charted by Dutch navigators a few years earlier.

How many new southern constellations, from Keyser and de Houtman's observations, appeared in the 1603 Uranometria?

All 12 were charted on the first Dutch voyage to the East Indies in 1595-97; they include Pavo the peacock, Tucana the toucan, Chamaeleon, Volans the flying fish and Apus the bird of paradise.

In a name like 'Alpha Centauri', what grammatical case of the constellation's Latin name follows the Greek letter?

Genitive means Alpha Centauri is literally 'Alpha of the Centaur' and Alpha Tauri 'Alpha of the Bull'; Flamsteed numbers use the same possessive form.

Which 17th-century Gdańsk astronomer and brewer introduced Canes Venatici, Sextans and Leo Minor?

Johannes Hevelius (1611-87), who ran his family's Gdańsk brewery, charted ten new constellations in his 1690 star atlas; seven of them, including Lacerta, remain among the 88.

Scutum, the Shield, was named in honour of which monarch's victory at the 1683 Battle of Vienna?

Hevelius named it Scutum Sobiescianum, Sobieski's Shield, in 1684 to honour John III Sobieski of Poland, whose army broke the Ottoman siege of Vienna the previous year.

Which faint constellation between Ursa Major and Auriga did Hevelius name after an animal?

Lynx, introduced by Hevelius in 1687, fills an otherwise empty patch between Ursa Major and Auriga; he said only the lynx-eyed could make it out, as none of its stars beats third magnitude.

Which 'serpent-bearer' constellation does the Sun cross each year without being a zodiac sign?

The Sun crosses Ophiuchus for about three weeks, from 30 November to 18 December, yet astrology's twelve signs are equal 30-degree slices that ignore constellation boundaries entirely.

The serpent-bearer constellation is identified with which Greek healer whose staff symbolises medicine?

Asclepius, son of Apollo, reputedly learned to raise the dead after watching one snake revive another with herbs; Zeus struck him down with a thunderbolt to keep humans mortal, then set him among the stars.

Which constellation is uniquely split into two parts, Caput in the west and Cauda in the east?

Serpens is divided into Serpens Caput, the head, and Serpens Cauda, the tail, by Ophiuchus, the man holding the snake; the tail section contains the Eagle Nebula, home of the Pillars of Creation.

Which is the only zodiac sign represented by an inanimate object?

Libra, the scales, was once seen as the claws of neighbouring Scorpius; its two brightest stars keep Arabic names meaning 'southern claw' (Zubenelgenubi) and 'northern claw' (Zubeneschamali).

Into which constellation has the 'First Point of Aries' drifted due to precession?

The vernal equinox point has slid westward into Pisces, moving about one degree every 72 years; the name was fixed over 2,000 years ago when the equinox really lay in the Ram.

The Crab Nebula, remnant of a supernova seen from Earth in 1054, lies in which zodiac constellation?

The Crab Nebula (M1) lies near Zeta Tauri in Taurus, which also holds the Pleiades and the Hyades; Chinese records say the 1054 supernova was visible by day for about three weeks.

Which of the celestial Twins is actually brighter, though its sibling got the 'Alpha' designation in 1603?

Pollux, an orange giant of magnitude 1.1, outshines Castor at 1.6, yet Bayer lettered Castor Alpha Geminorum in 1603; Pollux also hosts a confirmed exoplanet, Pollux b.

Which red supergiant on Orion's shoulder dimmed by about a factor of three in the 'Great Dimming' of 2019–20?

Betelgeuse takes its name from Arabic for 'the hand of al-Jawza', and is expected to explode as a supernova sometime within the next 100,000 years.

Alnitak, Alnilam and Mintaka form which famous part of the hunter Orion?

Alnitak, Alnilam and Mintaka make up Orion's Belt; extend their line to the south-east and it points straight at Sirius, the brightest star in the night sky.

The Orion Nebula, one of the brightest nebulae in the sky, hangs from which part of the hunter's figure?

The Orion Nebula (M42) is the middle 'star' of Orion's Sword, hanging below the Belt; at around 1,300 light-years it is the closest region of massive star formation to Earth.

In Greek myth, which creature killed Orion, which is why its constellation never shares the sky with the hunter?

A scorpion sent by Artemis and Leto, in one version, after Orion boasted he would kill every animal on Earth; as one rises in the east, the other sets in the west.

Which red supergiant marks the heart of Scorpius?

Antares, 'rival of Ares', earned the name because its reddish hue can be mistaken for Mars when the planet passes nearby, roughly every two years; it is a red supergiant about 550 light-years away.

Sirius, the brightest star in the night sky, belongs to which constellation?

Sirius, the 'Dog Star', lies just 8.6 light-years away in Canis Major, the Greater Dog, pictured chasing Lepus the Hare at the heels of Orion.

Which asterism joins Sirius, Procyon, Capella, Aldebaran and Rigel around Betelgeuse?

The Winter Hexagon, also called the Winter Circle, joins Rigel, Aldebaran, Capella, Pollux, Procyon and Sirius; it dominates northern evening skies from about December to March, with Betelgeuse near its centre.

Polaris, the North Star, is the brightest star of which northern constellation?

Ursa Minor's Polaris sits at the tip of the Little Dipper's handle, and despite its fame it is only about the 47th-brightest star in the sky.

Which star in the Dragon was the pole star around 2750 BC, when the Egyptian pyramids were being built?

Thuban, Alpha Draconis, sat nearest the pole around 2750 BC; Earth's axis wobbles in a 26,000-year cycle, so the honour rotates, and Vega gets the job around 14,000 AD.

The Big Dipper is not a constellation at all but an asterism inside which one?

Ursa Major, the Great Bear, is the third-largest constellation; its seven famous Dipper stars have been seen as a wagon, a bear and even a saucepan in different countries.

In the UK, the seven-star pattern Americans call the Big Dipper is usually known as what?

Older British sources call it Charles's Wain, and the Romans saw the same stars as seven oxen, whose ploughing 'herdsman' is the neighbouring Boötes.

Which two stars at the edge of the Big Dipper's bowl point the way to the North Star?

Dubhe and Merak, the Pointers, lie at the bowl's outer edge; follow the line from Merak through Dubhe for about five times their separation and you land almost exactly on Polaris.

Which Big Dipper handle pair, the Arabs' 'horse and rider', served as a traditional eyesight test?

Mizar and Alcor, the 'horse and rider' at the bend of the handle, are 12 arcminutes apart; Alcor is bright enough to see, but separating it from Mizar with the naked eye was the test.

In Greek myth, which jealous goddess turned Callisto into the Great Bear as punishment?

Callisto's son Arcas nearly speared his own mother while hunting before Zeus placed them both in the sky, and Hera then persuaded the sea gods never to let the bears bathe below the horizon.

Which W-shaped northern constellation is named for a vain queen who boasted of her beauty?

Cassiopeia was set in the sky to spend half of every night hanging upside down as punishment, and Tycho Brahe's supernova of 1572 blazed among her stars.

Which constellation depicts the hero who beheaded Medusa and rescued a chained princess?

Perseus holds the eclipsing binary Algol, the 'Demon Star' marking Medusa's severed head, and the August Perseid meteor shower, one of the year's best, radiates from it.

Messier 31, the nearest major galaxy to the Milky Way, is named after and lies in which constellation?

The Andromeda Galaxy, about 2.5 million light-years away, is the most distant object most people can see with the naked eye; the constellation shares its corner star Alpheratz with the Great Square of Pegasus.

Vega is the brightest star of which small northern constellation?

Lyra, Orpheus's lyre, also holds the Ring Nebula (M57), one of the best-known planetary nebulae; Vega was the pole star around 12,000 BC and will be again around AD 14,000.

The centre of the Milky Way lies in which constellation, whose brightest stars form the 'Teapot'?

The supermassive black hole at the galactic core is Sagittarius A*, and the mysterious 1977 'Wow!' radio signal also came from this direction.

Alpha and Beta of which constellation are the 'southern pointers' to the true Southern Cross?

Centaurus holds Alpha Centauri, the closest star system to the Sun at 4.4 light-years, and Omega Centauri, the largest globular cluster in the Milky Way; Alpha and Beta Centauri point to Crux.

Which country's flag depicts the sky on the morning its republic was proclaimed in 1889?

Brazil's flag shows the sky over Rio de Janeiro on 15 November 1889, the morning the republic was proclaimed; its 27 stars stand for the states and Federal District, with only Spica above the 'Ordem e Progresso' banner.

Besides Australia and New Zealand, which two Pacific nations' flags show the Southern Cross?

Papua New Guinea's flag sets five white stars of the Southern Cross on black, and Samoa's sets five on a blue canton; New Zealand shows only four red stars, Australia five white ones.

Which constellation contains the south celestial pole and is named after a navigational instrument?

Octans, the octant, holds the south celestial pole; its 'pole star' Sigma Octantis is a feeble magnitude 5.4, which is why southern navigators steer by the Southern Cross instead.

In Aboriginal Australian astronomy, the 'Emu in the Sky' is traced not from stars but from what?

Dark dust clouds of the Milky Way form it: the emu's head is the Coalsack Nebula beside the Southern Cross, and the body and legs trail along the Great Rift to Scorpius.

Traditional Chinese astronomy divides the ecliptic into how many lunar 'mansions'?

The 28 mansions (xiù) are grouped into the Four Symbols, the Azure Dragon, Vermilion Bird, White Tiger and Black Tortoise, each governing seven of them.

Which constellation represents the hair an Egyptian queen sacrificed for her husband's safe return?

Coma Berenices, 'Berenice's Hair', recalls Berenice II, who offered her locks for her husband Ptolemy III's safe return from war; the constellation contains the north galactic pole and the rich Coma Cluster of galaxies.

Which of Donald Menzel's eight constellation families, spanning +60° to -70° declination, is the largest?

The Hercules Family is the largest, with 19 constellations from Lyra and Cygnus down to Ara and Crux; Menzel, a former Harvard Observatory director, laid out the families in his 1975 Field Guide to the Stars and Planets.

Which Belgian astronomer drew the IAU's official constellation boundaries, published in 1930?

Eugène Delporte of the Royal Observatory of Belgium drew the boundaries along lines of right ascension and declination for the IAU's 1930 Délimitation scientifique des constellations; he also discovered 66 asteroids, including 1221 Amor.

In which small constellation did Jocelyn Bell detect the first pulsar in 1967?

Vulpecula, the little fox, holds PSR B1919+21, the pulsar Bell found in 1967, and the Dumbbell Nebula, the first planetary nebula Charles Messier catalogued, in 1764.