The first planet orbiting Upsilon Andromedae was discovered in 1996 by researchers at San Francisco State University. But researchers noticed an irregularity to their results, suggesting that their explanation of the star's "wobbling" was incomplete.

"It became clear that there was another component of the system that could only be discovered by examining long-term trends in the data," Nisenson said.

Nisenson also pointed out that two of the discovered planets were within "the habitable zone," the distance from a star that corresponds to planets with temperatures roughly similar to those of Venus, Earth and Mars.

"There's no reason not to think that these planets might have moons that might have life on them," Nisenson said.