There are 88 constellations in the night sky. Each one is a straight-edged area of sky that it includes a pattern made from bright A stars, and they all fit together like pieces of a jigsaw to make up the entire sky around Earth.
Who’s who in the sky
Thirteen constellations feature humans. Twelve come from Greek mythology, and the thirteenth is Native American.
The 15 animal constellations include a bull and a wolf.
The eight birds include a peacock and a toucan.
A crab, a dolphin, and a sea monster are amongst nine water-based constellations.
Twenty-eight objects include a harp, a compass, a cross, a clock, and a microscope.
The remaining 15 are a miscellany, from a fly to mythical creatures.
Far, far away
The stars in a particular pattern only appear close together in space. In fact, the stars are totally unrelated and at vastly differing distances from Earth.
How to : spot Orion
- Face the horizon. Hold out your arm with hand outstretched. Orion is a little bigger than your hand. If you are in the southern hemisphere, Orion appears upside down.
- Look for a row of three bright stars very close together in the sky. This is his belt.
- At equal distance one above and one below the belt, are two bright stars. The brightest, with a warm red glow, is Betelgeuse. The whiter star is Rigel
Tell me more: the celestial sphere
- Ancient astronomers imagined the night sky as a giant sphere of stars rotating around the Earth.
- The idea of a celestial sphere is still used to describe a star’s position.
- The sphere is divided into the 88 constellations.
- The outline of the Orion constellation (left) is shown in orange.
Blasts from the past
2000 BCE
The first constellations are devised by Sumerians and Babylonions.
150 CE
Greek astronomer Ptolemy fist 48 constellations.
1596-1603
Twelve constellations are introduced by Dutch navigators Peter Keyser and Frederick de Houtman.
1690
Seven new constellations complete the northern sky.
1754
Fourteen constellations are introduced by French astronomer Nicolaus de Lacaille to complete the southern sky.
1922
The 88 constellation patterns are sanctioned by the International Astronomical Union.
1930
The constellations’ straight-edge official boundaries are agreed.
You won’t believe it!
The star patterns aren’t going to last for ever, but neither are they going to change any time soon. All stars are moving at about 50-100 km (30-60 miles) a second, but we can hardly tell because they are so far away. Constellation stars are typically 100 light years away, and so it takes us about 10,000 years before we start to notice a star’s changing position.
The biggest constellation is Hydra, a water snake that meanders its way across 3.16 per cent of the whole sky. The smallest constellation is Crux, the southern cross, which is also the brightest constellation.
WEIRD OR WHAT?
The strangest constellation has got to be a head of hair. its official name is Coma Berenices, because it is named for the hair of Berenice, the Queen of Egypt.
The Zodiac
Twelve constellations form the backdrop to the Sun’s path across the stars. Together they are known as the Zodiac.
The Sun completes one circuit of the Zodiac in a year, taking about a month to pass through each constellation.
The word “Zodiac” comes from the Greek for animal and, with one exception, is a circle of creatures. Libra, the scales, was introduced, long alter the others.
- Aries
- Taurus
- Gemini
- Cancer
- Leo
- Virgo
- Libra
- Scorpio
- Sagittarius
- Capricorn
- Aquarius
- Pisces
Starry dogs
There are four dogs in the sky. Two make the constellation Canes Venatici, the hunting dogs. The other two are Orion’s hunting dogs, Canis Major (Large Dog) and Canis Minor (Small Dog).
The star Sirius, in Carlin Major, is the brightest star in the sky. It is sometimes called the Dog Star.
The ancient Greeks and Romans called the hottest days of summer “the dog days ” because these were the days when Sirius rose in the Sky as the Sun set.
Sirius is, in fact, a double star. Its companion, Sirius B, is fondly known as “the pup”.
Dutch artist Vincent van Gogh shows the Plough in his painting Starry Night Over the Rhône.
Great Bear: Bear necessities
- There are two bears in the sky, Ursa Major (Great Bear) and Ursa Minor (Little Bear). They are both found in northern hemisphere skies.
- One of the most famous stars of all is Polaris, the Pole Star, at the tip of Ursa Minor’s tail. It lies above Earth’s North Pole.
- No one knows why both bears are given long tails, as real bears have short stubby tails.
One of the best-known patterns in the night sky, the Plough, is not a constellation but a star pattern known as an asterism. The seven stars are part of Ursa Major, the Great Bear.