Historically, stars have been important tocivilizationsthroughout the world. They have been part of religious practices and used forcelestial navigationand orientation. Many ancient astronomers believed that stars were permanently affixed to aheavenly sphere, and that they were immutable. By convention, astronomers grouped stars intoconstellationsand used them to track the motions of theplanetsand the inferred position of the Sun.

It helps tell us how we got all the other elements that make up things around us (and in us!). By the way, since your bodies are made of elements like carbon, oxygen, etc., that means that you are made up of atoms that used to be part of a star!

Another reason to study stars is that what we learn from other stars may help us understand our own Sun, which is also a star. The Sun only seems different to us because it is so much closer to us than other stars. Understanding our own Sun is important since it is ultimately the source of most of the energy we use on earth. It is what keeps the Earth warm enough for us to live on and it provides the light needed for plants and animals to stay healthy.

When we study stars, we also learn something about how they are born and die. This helps us understand how our own solar system was formed. We now think that our solar system was formed about 4.55 billion years ago and that it was created from a big interstellar cloud of gas, dust, and ice that slowly collapsed into the shape of a disk. The materials in this disk then clumped together to form the Sun and planets. Disks like the one we think formed our Solar System have now been detected around other stars in our galaxy.

Understanding stars is also important because stars contain a large fraction of all the visible mass in galaxies. As a result, their combined gravitational forces affect the 'dynamics' of galaxies, i.e. the ways in which galaxies move and evolve in shape. Our own galaxy is shaped like a disk with a central 'bulge.'. Since our Solar System is in the disk, the galaxy looks like a stripe of stars to us. We call the stripe the "Milky Way." You can easily see the Milky Way at night if the sky is dark where you live.

The gravitational pull of one particular star, our Sun, is especially important since it is the Sun's gravitational attraction that keeps the Earth in orbit. Without the Sun's gravity, the Earth would fly off into space and freeze!

The motion of the Sun against the background stars (and the horizon) was used to createcalendars, which could be used to regulate agricultural practices. TheGregorian calendar, currently used nearly everywhere in the world, is asolar calendarbased on the angle of the Earth's rotational axis relative to its local star, the Sun.The firststar catalogueinGreek astronomywas created byAristillusin approximately 300 BC, with the help ofTimocharis.The star catalog ofHipparchus(2nd century BC) included 1020 stars and was used to assemblePtolemy's star catalogue. Hipparchus is known for the discovery of the first recordednova(new star). Many of the constellations and star names in use today derive from Greek astronomy.Medieval Islamic astronomersgaveArabic names to many starsthat are still used today, and they invented numerousastronomical instrumentsthat could compute the positions of the stars. They built the first largeobservatoryresearch institutes, mainly for the purpose of producingZijstar catalogues. Among these, theBook of Fixed Stars(964) was written by thePersianastronomerAbd al-Rahman al-Sufi, who observed a number of stars,star clusters(including theOmicron VelorumandBrocchi's Clusters) andgalaxies(including theAndromeda Galaxy). According to A. Zahoor, in the 11th century, the PersianpolymathscholarAbu Rayhan Biruni described theMilky Waygalaxy as a multitude of fragments having the properties ofnebulousstars, and also gave the latitudesof various stars during alunar eclipsein 1019.