Daily Times

They’re not too hot, not too cold, and may provide just the right conditions for life to form. Astronomers have found three Earth-sized worlds within the so-called habitable ‘Goldilocks’ zone of a nearby star.

The scientists believe at least one of these ‘three bears’ planets may be ‘just right’ for life to get going, giving the search for life elsewhere in the universe a significant boost.

The star is around 40 light-years away. By comparison Mars is, on average and based on its orbit, 12.5 light-minutes away.

The international team of astronomers that found the planets said they are orbiting an ultracool brown dwarf star about one-eighth the size of our sun called 2MASS J23062928-0502285.

Also known as Trappist-1, this dim and cool star fades slightly at regular intervals, indicating several objects are passing between the star and the Earth.

Detailed analysis has now shown that three planets with similar sizes to the Earth are present.

Trappist-1 is much cooler and redder than the sun and barely larger than Jupiter. It lies in the constellation of Aquarius. Such stars are both very common in the Milky Way and are very long-lived, but this is the first time planets have been found around one of them.

Despite being so close to the Earth, this star is too dim and too red to be seen with the naked eye or even visually with a large amateur telescope.

According to Michaël Gillon of the University of Liège, Belgium, the planetary system looks more like moons orbiting Jupiter than our conventional idea of a solar system.

“The planets are 20 to 100 times closer to their star than Earth is to the sun,” he explained.

“This is more similar in scale to the system of Jupiter’s moons than the solar system.”

The team used a modest 60cm telescope, based in Chile, to find the planets.

The astronomers believe all three may be habitable, and they are now turning larger instruments on these new worlds to find out more.

While other exoplanet searches have concentrated on bright stars, Gillon and his team set up the Trappist survey specifically to scan the 60 nearest dwarf stars.

“Systems around these tiny stars are the only places where we could detect life on Earth-sized exoplanets with our current technology,” he said.

“So this is where we should start to look.”

In September 2015, Trappist-1 – was seen to fade slightly at regular intervals, showing that several objects were passing in front of it.

Further observations confirmed these were Earth-sized planets. The two innermost planets orbit in 1.5 and 2.4 days, while the third is less certain and might be anything between four and 73 days. The team believes this third ‘Daddy Bear’ planet is the most likely to be habitable out of the three.

In their report, published today in the journal Nature, the astronomers said all three planets are likely tidally locked to their dim star, with hemispheres of permanent night and day.

For the inner two, this might restrict any life-friendly sweet spots to the ‘twilight zone’.

But on the third, the whole planet may be able to support life. Because this solar system is relatively close, it should be possible to detect whether the planets have an atmosphere, and even to detect signs of life.

“We can study their atmosphere and composition and within our generation, assess if they are actually inhabited,” added co-author Julien de Wit, an astronomer at MIT. He added, “All of these things are achievable, and within reach now. This is a jackpot for the field.”