50 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?

The water snake is more than 100 degrees long but has only one reasonably bright star, Alphard, whose name means 'the solitary one'.

Which constellation is the smallest by area, yet one of the southern sky's most recognisable?

The Southern Cross covers just 68 square degrees, and the ancient Greeks knew its stars only as part of a neighbouring constellation before precession dropped them below Europe's horizon.

How many constellations did Ptolemy list in the Almagest in the 2nd century AD?

All but one of the figures survive today; the exception, a giant ship, was carved up in the 18th century.

Which ancient constellation, the ship of the Argonauts, was broken up into Carina, Puppis and Vela?

It is the only one of Ptolemy's 48 constellations no longer recognised as a single figure, and its brightest star Canopus now belongs to Carina, the keel.

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

He gave the southern sky an air pump, a furnace, a microscope, a telescope and a pendulum clock, and catalogued roughly 10,000 stars while he was at it.

Mensa is the only constellation named after a geographical feature on Earth. Which one?

It commemorates the flat-topped mountain overlooking Cape Town where its creator set up his telescope, and it is also the faintest of all 88 constellations.

Whose 1603 atlas Uranometria first covered the whole celestial sphere and introduced Greek-letter star labels?

He was a lawyer by profession, and his atlas also imported twelve brand-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?

They include a peacock, a toucan, a chameleon, a flying fish and a bird of paradise, all creatures the sailors had encountered on their voyages to the East Indies.

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

So Alpha Centauri literally means 'Alpha of the Centaur', and Alpha Tauri is '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?

He described ten new constellations in all, seven of which are still in use, and his famous Jopen beer gave its name to a street in Gdańsk.

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

It was first called Scutum Sobiescianum, Sobieski's Shield, and it is the only modern constellation that honours a real historical event.

Which faint northern constellation was named after a sharp-eyed animal, as only such eyes could make it out?

It fills an otherwise empty patch between Ursa Major and Auriga, and none of its stars is brighter than about third magnitude.

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

The Sun spends about three weeks there from late November to mid-December, but the twelve astrological 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?

Legend says he learned to bring the dead back to life after watching one snake revive another with herbs, and Zeus struck him down to keep humans mortal.

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

The head and tail are separated by the man holding the snake, and the tail section contains the Eagle Nebula, home of the Pillars of Creation.

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

The scales were once seen as the claws of neighbouring Scorpius, and its two brightest stars are still named 'southern claw' and 'northern claw' in Arabic.

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

The name was fixed over 2,000 years ago when the equinox really was in the Ram; the point creeps westward by about one degree every 72 years.

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

The same constellation holds the Pleiades and the Hyades, and Michael Rappenglück has argued the Bull is even painted on the cave walls at Lascaux.

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

The lettering mix-up happened because the atlas author did not carefully check which twin was brighter; the orange giant also has a confirmed exoplanet.

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

The name comes from Arabic for 'the hand of al-Jawza', and the star 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?

Extend the line of the three stars to the south-east and it points straight at 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?

At around 1,300 light-years away it is the closest region of massive star formation to Earth, and it looks like a fuzzy 'star' to the naked eye.

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

One version has Artemis and Leto sending the beast 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 at the heart of Scorpius has a name meaning 'rival of Mars'?

It earned the name because its reddish hue can be mistaken for the planet when Mars passes nearby, which happens roughly every two years.

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

The 'Dog Star' is only 8.6 light-years away, and the Greater Dog is pictured chasing Lepus the Hare at the heels of Orion.

Which giant asterism links Rigel, Aldebaran, Capella, Procyon, Sirius and one of the Twins?

Also called the Winter Circle, it dominates northern evening skies from about December to March, and the red shoulder star of Orion sits roughly at its centre.

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

It 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?

Earth's axis wobbles in a 26,000-year cycle, so the honour rotates: Vega gets the job around 14,000 AD.

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

The Great Bear is the third-largest constellation, and its seven famous 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?

Follow the line between them for about five times their separation and you land almost exactly on the pole star.

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

The fainter partner would normally be easy to spot, but it sits so close to its brighter neighbour that separating the two with the naked eye is the challenge.

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?

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

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

The August meteor shower that radiates from it is one of the year's best, and it contains the eclipsing binary Algol, the 'Demon Star' that marks Medusa's severed head.

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

At about 2.5 million light-years it is the most distant object most people can see with the naked eye, and it shares its corner star Alpheratz with the Great Square of Pegasus.

Vega is the jewel of which small constellation representing the lyre of Orpheus?

It also holds the Ring Nebula, M57, one of the best-known planetary nebulae, and Vega was the pole star around 12,000 BC.

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?

The same constellation holds Alpha Centauri, the closest star system to the Sun, and Omega Centauri, the largest globular cluster in the Milky Way.

Which country's flag depicts the stars over Rio de Janeiro on the morning of 15 November 1889?

Each of its 27 stars stands for a state or the Federal District, sized by the real star's brightness, and only Spica sits above the 'Ordem e Progresso' banner.

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

New Zealand shows only four red stars, Australia five white ones, and each flag standardises the shapes differently.

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

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?

The emu's head is the Coalsack Nebula beside the Southern Cross, and a rock engraving of it at Ku-ring-gai Chase near Sydney matches the figure's pose.

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

They are grouped into the Four Symbols, the Azure Dragon, Vermilion Bird, White Tiger and Black Tortoise, each governing seven mansions.

Which is the only modern constellation named after a real person, an Egyptian queen who sacrificed her hair?

Berenice II offered her locks for her husband's safe return from war; the constellation also 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?

Menzel, director of the Harvard Observatory, laid out the families in his 1975 Field Guide to the Stars and Planets, grouping constellations by myth, position or origin.

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

He also discovered 66 asteroids, including 1221 Amor, which gave its name to a whole class of near-Earth objects.

Alpha and Beta Delphini bear the odd names Sualocin and Rotanev. What is their secret?

Nicolaus Venator was the Latin form of Niccolò Cacciatore, an assistant at Palermo Observatory who slipped the joke into an 1814 star catalogue.

In which small constellation, the 'little fox', did Jocelyn Bell detect the first pulsar in 1967?

The same patch of sky holds the Dumbbell Nebula, the very first planetary nebula Charles Messier ever catalogued, in 1764.