In a recent groundbreaking discovery, researchers were able to spot three potentially habitable planets similar to Earth revolving around an ultracool dwarf star located 40 light years away from our planet, in another star system.

In a study published in the journal "Nature," the space scientists explained how they discovered the exoplanets by focusing on the dwarf star known as TRAPPIST-1, which was previously overlooked by astronomers.

TRAPPIST-1, first discovered by a team of scientists last year, is a red, ultracool star a bit larger than Jupiter. Astronomers shied away from studying this dwarf star in the past because it was too dim to be seen with the naked eye or even amateur telescopes from Earth.

While observing the dwarf planet, astronomers saw something out of the ordinary: There were shadows, similar to little eclipses, periodically interrupting the steady pattern of starlight, prompting them to suspect that there are other space objects circling TRAPPIST-1.

Professor Adam Burgasser of the Center for Astrophysics and Space Science at the University of California San Diego, one of the researchers, said this drew the curiosity of his team.

"It's like standing in front of a lamp and throwing a flea across it. It was only a 1 percent dip in light, but the specific pattern was a good sign of orbiting planets," Burgasser said in an interview with CNN.

With the help of a telescope that can detect infrared light, the researchers found the three planets about the size of Earth.

Two of them receive about four times the amount of radiation than we do from the sun due to their distance from the dwarf planet, but space scientists think they are still in a "habitable zone."

These two planets are also believed to be tidally locked, or with one side permanently experiencing nighttime and the other, daytime.

Little is known about the third planet, except that it gets twice the amount of radiation than we do from the sun. The researchers nevertheless also think that it is likely habitable.

Burgasser said the three Earth-like planets may still have water on its surfaces—a key ingredient for life.

"We've shown that these kinds of stars are a way to find Earth-like planets," he said. "Over the next few years, we can explore the space around this one and pin down their orbits and see if there are other planets in this system."