Earth-like planet discovered
WASHINGTON — Astronomers have found yet another planet that seems to have just the right Goldilocks combination for life: Not so hot and not so cold. It’s not so far away, either.
This new, big, dense planet is rocky, like Earth, and has the right temperatures for water, putting it in the habitable zone for life, according to a study published yesterday in the journal Nature.
It’s the fifth such life-possible planet outside our solar system revealed in less than a year, but still relatively close to Earth.
Rocky planets within that habitable zone of a star are considered the best place to find evidence of some form of life.
“It is astonishing to live in a time when discovery of potentially habitable worlds is not only commonplace but proliferating,” said MIT astronomer Sara Seager.
The first planet outside our solar system was discovered in 1995, but thanks to new techniques and especially NASA’s planet-hunting Kepler telescope, the number of them has exploded in recent years. Astronomers have now identified 52 potentially habitable planets and more than 3,600 planets outside our solar system.
The latest discovery — called LHS 1140b — regularly passes in front of its star, allowing astronomers to measure its size and mass. That makes astronomers more confident that this one is rocky, compared to other recent discoveries.
In the next several years, new telescopes should be able to use the planet’s path to spy its atmosphere in what could be the bestaimed search for signs of life, said Harvard astronomer David Charbonneau, a co-author of the study. If scientists see both oxygen and some carbon in an atmosphere, that’s a promising sign that something could be living.
“This is the first one where we actually know it’s rocky,” Charbonneau said. “We found a planet that we can actually study that might be actually Earth-like.”
Compared to Earth, the new planet is big, pushing near the size limit for rocky planets. It’s 40 percent wider than Earth but it has 6.6 times Earth’s mass, giving it a gravitational pull three times stronger, Charbonneau said. A person weighing 167 pounds would feel like 500 pounds on this planet.
In the constellation Cetus, it is 39 light years, or 230 trillion miles, away. So are a group of seven mostly Earth-sized planets in or near the habitable zone found circling a star called Trappist-1 earlier this year, but in a different direction.
“If you picture the Milky Way as the size of the United States, then these systems are all within the size of Central Park,” Charbonneau said. “These are your neighbors.”