Astronomers have used telescopes for hundreds of years. But to get the best data, the telescope needs to be in space! This is because the Earth's air interferes with the light which travels through it. It acts like a blanket, letting through some waves of light and blocking others. This can make images of far away objects look blurry. Or it stops us from seeing them completely. Plus, space telescopes don't have the problem of light pollution.
Building and using a space telescope is a huge challenge. It has only been possible in the last few decades. The first space telescope was the Hubble Space Telescope. It began observing in 1990 and has made over 1 million observations since.
Hubble paved the way for others, including the massive James Webb Space Telescope. Some collect light which the Earth's atmosphere blocks out. Telescopes like Chandra and Fermi observe x-rays and gamma rays. Others can see microwaves or infrared. This has given us a new view of our Universe. It has increased our knowledge of how physics works in extreme environments, such as quasars.
Space telescopes have made fantastic discoveries. Kepler found thousands of exoplanets. Spitzer was the first to capture light from an exoplanet. Gaia observed a supernova outside the Milky Way. In the future, LISA will detect gravitational waves in space.