Astronomers have found the star, known as TRAPPIST-1. It is a small, dim celestial body in the constellation Aquarius. It is located about 40 light years away from Earth, close by astronomical standards, but about 44 million years away at the average cruising speed of a commercial passenger jet.
The discovery builds on previous research showing three planets circling TRAPPIST-1. They are among more than 3,500 planets discovered beyond the solar system, or exoplanets.
This is the first time that so many Earth-sized planets are found around the same star.
The diameter of TRAPPIST-1 is about 8 percent of the sun’s size. That makes its Earth-sized planets appear large as they parade past.
From the vantage point of telescopes on Earth, the planets’ motions regularly block out bits of the star’s light. Scientists determined the system’s architecture by studying these dips.
Because TRAPPIST-1 is so small and cool, its so-called “habitable zone” is very close to the star. Three planets are properly positioned for liquid water.
TRAPPIST-1 is at least 500 million years old, but has an estimated lifespan of 10 trillion years. The sun, by comparison, is about halfway through its estimated 10-billion-year life.