What is Constellation?
A group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure.
Throughout the centuries, people have looked to the stars to help them navigate deserts & sea, know when to plant and harvest etc. Ancient peoples used the appearance or disappearance of certain stars over the course of each year to mark the changing seasons. To make it easier to “read” this celestial calendar, they grouped the brighter stars into readily recognizable shapes, the constellations.
How many constellations are there?
There are 88 official constellations. But astronomers haven’t made up new constellations for hundreds of years! When new stars are discovered, they are considered to be a part of whatever constellation they are closest to.
Who invented them?
Our modern constellation system comes to us from the ancient Greeks. The oldest description of the constellations as we know them comes from a poem, called Phaenomena, written about 270 B.C. by the Greek poet Aratus. However, it is clear from the poem that the constellations mentioned originated long before Aratus’ time. No one is sure exactly where, when, or by whom they were invented.
Where do individual star names come from?
Most of the brightest stars are named after characters in the mythology from various cultures. Many of them (like the planets) therefore have different names depending on where you are in the world. They were often named in pre-history by our ancestors who gazed at the stars trying to find patterns and stories in what they saw (this is also where the names for the visible planets and the constellations came from).
Modern astronomers have given the stars new names so that they can keep track of them more easily. Stars are named for the constellation that they lie in with the brightest star in a constellation being alpha and so on throught the greek alphabet. For example, Betelguese which is the brightest star in the constellation Orion, is also called Alpha Orionis.
Did other cultures also see constellations in the sky?
Nearly every culture on Earth has seen patterns in the stars. But, not surprisingly, very few have seen the same patterns. Take, for example, the Big Dipper, perhaps the most recognizable star pattern in the sky. The Big Dipper is not actually a constellation itself, but is part of a larger pattern known to the Greeks as Ursa Major, the Great Bear. The seven stars of the Big Dipper have inspired many stories, perhaps because they are bright and located so near the north celestial pole, around which the stars rotate during the course of the night. But not everyone calls it a Dipper. The British call it a Plough. In Southern France, it is a Saucepan. The Skidi Pawnee Indians saw a stretcher on which a sick man was carried. To the ancient Maya, it was a mythological parrot named Seven Macaw. Hindu sky lore called it the Seven Rishis, or Wise Men.
Are all the stars in a constellation the same distance away from us?
No. With few exceptions, the stars in a constellation have no connection with one another. They are actually at very different distances from the sun, alignments of stars have created the patterns we see in the sky.
Are the constellations patterns permanent?
The motion of stars is quite small at a few or a few tens of km/s. However, they are situated several light years away from us. let us take an example. Let a star be situated about 10 light years away from us (note that this is a nearby star) and move at 10 km/s. Then, in 100 years, the movement is approximately 30 billion km. The distance of the star from us in comparison is 90,000 billion kilometers. So its motion in 100 years is so small compared to its distance that we see the star in the same spot in the sky. However, if one waits for a few hundred thousand years, then one can definitely see the constellations change.
What is the largest constellation?
Hydra, (“Water Snake”) takes up 3.158% (1303 square degrees) of the night sky, making it the largest star constellation in the night sky. This southern hemisphere constellation can be seen from between +54° and -83° of latitude, although best seen in April. It’s head is located just to the south of Cancer, with the rest of its long, twisting body stretching all the way to a point between Centaurus and Libra, where its tail terminates. Hydra contains around 238 stars, but consists primarily of an asterism of 17 stars, the brightest of which is Alphard, an orange giant of magnitude +2 located 177 light-years distant. In Greek mythology, Hydra is associated with the Lernaean Hydra from the Twelve Labours of Heracles.
Virgo is the second-largest constellation (of the 88 constellations), after Hydra.