Astronomers have used telescopes to look at the night sky for hundreds of years. To get the best data though the telescope needs to be in space! This is due to the Earth's atmosphere. The air causes light to bounce around which can make images look blurry. It also acts like a blanket, letting through some types of light and blocking others. This means we don't see all the light from an object.
Space telescopes also get away from human-made light on Earth. This makes faint objects hard to see from the ground. We call this light pollution.
Building and using a space telescope is a huge challenge. It also costs a lot of money. It has only been possible since the 1980s. One of the most renowned space telescopes is the Hubble Space Telescope. It began observing in 1990 and has taken over 1 million images so far.
Since 1990 there have been lots of other space telescopes. Some collect light which the Earth's atmosphere blocks out. Like Chandra which observes in x-rays and Fermi which looks at gamma rays. Others can see microwaves or infrared. This has given us a new view of our Universe. The largest, James Webb Space Telescope, will launch in December 2021.
Space telescopes have made many fantastic discoveries. Kepler found thousands of exoplanets. Spitzer was the first to image light from an exoplanet. Gaia observed a supernova outside the Milky Way. In the future, LISA will try to detect gravitational waves in space.