Unlike most exoplanet discoveries, which are inferred from analysis of data, the planets of the HR8799 system are directly visible from Earth. The planets were discovered in 2008 using the Keck and Gemini telescopes in Hawaii. The star HR8799, about 1.5 times the size of the sun and about five times brighter, lies 130 light years from Earth. Each of the star's four known planets is larger than any planet in our solar system. The star formed only 30 million years ago and is a variable star, meaning that its luminosity changes over a period of about half a day. By studying light reflected from planet HR8799c, astronomers have found water and carbon monoxide in its atmosphere.
Via Dr. Stefan Gruenwald