Star facts: History, formation and classification

Astronomers are constantly learning new star facts as space exploration and technology evolves. To make sense of these new findings, it’s important to know the basics. Stars are giant, luminous spheres of plasma. There are billions of them — including our own sun — in the Milky Way galaxy. And there are billions of galaxies in the universe. So far, we have learned that hundreds also have planets orbiting them.

History of observations

Since the dawn of recorded civilization, stars played a key role in religion and proved vital to navigation, according to the International Astronomical Union. Astronomy, the study of the heavens, may be the most ancient of the sciences. The invention of the telescope and the discovery of the laws of motion and gravity in the 17th century prompted the realization that stars were just like the sun, all obeying the same laws of physics. In the 19th century, photography and spectroscopy — the study of the wavelengths of light that objects emit — made it possible to investigate the compositions and motions of stars from afar, leading to the development of astrophysics

In 1937, the first radio telescope was built, enabling astronomers to detect otherwise invisible radiation from stars. The first gamma-ray telescope launched in 1961, pioneering the study of star explosions (supernovae). Also in the 1960s, astronomers commenced infrared observations using balloon-borne telescopes, gathering information about stars and other objects based on their heat emissions; the first infrared telescope (the Infrared Astronomical Satellite) launched in 1983. 

radio telescope

Radio waves from radio telescopes can pass through clouds to observe the stars. (Image credit: Getty Images)