4 Alien Huge Planets Spotted Around Baby Star

In an astronomical first, four gigantic planets have been detected around a very young star, a new study reports.

The star in question is CI Tau, which is about 500 light-years from Earth. CI Tau is just 2 million years old and is still surrounded by a swirling clone of a protoplanetary disk.

The star was already known to host one planet, a world about 10 times more massive than Jupiter that circles CI Tau once every nine days. This planet, called CI Tau b, was the first "hot Jupiter" ever discovered around such a young star. [Gallery: The Strangest Alien Planets]

In the new study, a team of researchers observed CI Tau and its disk with the Atacama Large Millimeter / submillimeter Array (ALMA), a network of radio telescopes in the Chilean Andes. ALMA spotted three additional gaps in the disk, at distances of 13, 39 and 100 astronomical units (AU) from the star, the astronomers report. (One AU is the Earth-sun distance – about 93 million miles, or 150 million kilometers).

So it seems that CI Tau has three siblings. And these newfound worlds are big, too: The team's work suggests that Jupiter, while the other two have Saturn-esque heft.

Astronomers had never spotted a gas-giant planets around such a young star. And the orbital range – the outermost planet is about 1,000 times farther from CI Tau than the innermost world.

Indeed, it's unclear how the two outermost planets were able to take shape.

"Saturn-mass planets are supposed to be formulated by a group of people," Cathie Clarke, study lead author The Institute of Astronomy at the University of Cambridge, England, said in a statement. "Most models will struggle to make planets of this mass at this distance."

It's also unclear what role, if any, the sibling planets played in driving CI Tau b to its super tight orbit, study team members said. Observing the weird system with other telescopes may help answer these and other questions, study team members said.

The new paper was published in the Astrophysical Journal Letters.

Mike Wall's book on the search for alien life, "Out There," will be published on Nov. 13 by Grand Central Publishing. Follow him on Twitter @michaeldwall. Follow us @Spacedotcom or Facebook. Originally published on Space.com.