Giant planet quartet

Four gas giants were recently spotted around a star, CI Tau, that is only two million years old. This is the first time so many planets have been found around such a young star and astronomers are struggling to explain how they could have formed this quickly.

Observations with the Atacama Large Millimetre/ submillimetre Array revealed that the innermost planet is an example of a hot Jupiter, orbiting 1,000 times closer to the star than the outermost one. It’s thought hot Jupiters are forced into their tight orbits via gravitational interactions with other worlds in their systems, and so researchers will continue studying CI Tau to gain clues about how extreme planet systems form. www.almaobservatory.org

CI Tau’s two outer planets are about the mass of Saturn; its inner ones are one and 10 times the mass of Jupiter