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Ancient peoples first looked up thousands of years ago, and the stars were there; pinpoints of light that seemed to slowly rotate around the Earth. The first astronomers also noticed the planets, the Moon and the Sun, and their motions across the night sky. Let’s learn about the history of stars.
We now know that stars are hot balls of hydrogen and helium, with nuclear fusion at their core. They can live billions and even trillions of years, consuming their hydrogen fuel. But ancient peoples had no idea what they were.
But they’ve always been important. The stars played a part in religious ceremonies, and navigators used them to travel at night, both over land and at sea. Early astronomers grouped the stars into constellations, and then used these to track the movement of the Sun and the planets. The motions of the stars over the course of a full year helped them build the first accurate calendars, to know when to plant fields and when to harvest.
In 1584, Giordana Bruno proposed that stars were other objects like our Sun, just much further away. Astronomers then started measuring changes in the luminosity of stars, and even the proper motion of nearby stars; they had changed their position since they were first measured by the ancient Greek astronomers Ptolemy and Hipparchus. The first measurement of distance to star was made by Friedrich Bessell in 1838 using the parallax technique – 61 Cygnus was measured to be 11.4 light years away.
In the 20th century, astronomers finally started using photography to image stars, and techniques were developed to measure the spectra of light coming off them. Theoretical advances in physics helped explain the different colors of stars and how this matched their luminosity and temperature.
We now know that our Milky Way galaxy contains between 200 and 400 billion stars and that there could be as many as 500 billion galaxies out there with just as many stars. Individual stars are mostly seen in our galaxy, but they have been imaged as far away as 100 million light-years.