Two new planets 8-times the size of Earth could support life — and they're right next-door

Artist’s concept of GJ229Ac, the nearest temperate super-Earth to us that is in a system in which the host star has a brown dwarf companionRobin Dienel/Carnegie Institution for Science​
  • Scientists have found two new habitable planets, nearly 8 times the size of Earth, that don’t orbit a ‘Goldilocks’ star.
  • These are the closest candidates to Earth to support human life on another planet.
  • A year on, these red dwarf stars orbiting Super-Earths would only last a little over 100 days.
Finding a planet other than Earth to support human life is astronomy’s moonshot project. Two new ‘Super-Earths’ — that don’t orbit a ‘Goldilocks’ star — could be potential candidates.

GJ180D and GJ229A are nearly eight times the size of Earth will have shorter years. They are the closest planets to Earth that could be capable of supporting life, according to a new study published in The Astrophysical Journal Supplement Series.

An artist’s concept of GJ180d, which is the nearest temperate super-Earth to us that is not tidally locked to its star, making it more likely to be able to host and sustain lifeRobin Dienel/Carnegie Institution for Science​

Earth’s closest alternatives
GJ229A and GJ180D orbit two different stars. One is 19 light-years away and the other is at a distance of 40 light-years, respectively. Since these planets are so close to Earth, they can be the next prime targets for observations by space and land-based telescopes.

They’re also much bigger. GJ229A is 7.9 times the size of our planet while GJ180D is 7.5 times bigger. Their size is why scientists categorise them as ‘Super-Earths’.

However, the length of a year on each planet is nearly one-third of how long a year would be on Earth. On GJ229A, it would only last 122 days and be even shorter on GJ180D of around 102 days.


Red dwarf stars aren’t ‘just right’ but can still support life
Scientists describe ‘Goldilocks’ stars as stars which are the perfect temperature to host life on planets nearby. However, every star is different and there is no right answer.

Even, the Sun — a yellow dwarf G-type main-sequence star — isn’t a Goldilocks star, yet life thrives on Earth. In the case of the newly discovered Super-Earths, they orbit red dwarf stars, also not considered to be ideal.

Only K-dwarf stars, that fall somewhere in between the Sun and red dwarfs, are considered to be the perfect contenders.

However, there is one key difference between these Super-Earths orbiting a red dwarf star and other planets found orbiting similar stars — they’re not caught in a tidal lock.

“This is similar to how our Moon is tidally locked to Earth, meaning that we only ever see one side of it from here. As a result, these exoplanets are a very cold permanent night on one side and very hot permanent day on the other—not good for habitability,” explains Fabo Feng, lead author of the study.

Therefore, the Super-Earths don’t take the same amount of time to spin around their axis as they do to orbit around their respective stars.

“GJ180d is the nearest temperate super-Earth to us that is not tidally locked to its star, which probably boosts its likelihood of being able to host and sustain life,” explains Fabo Feng, lead author of the study.

A new way to find habitable Earth-like planets in the universe
These new worlds were discovered using the radial velocity method. This process doesn’t only look at how a planet orbits a star, but also the planet’s gravity might be affected by the star in return.

The resulting wobble in the star’s orbit can be detected from Earth using advanced instruments — like the Carnegie Planet Finder Spectrograph (PFS), High Accuracy Radial velocity Planet Searcher (HARPS) — which were used to find GJ180D and GJ229A.

The research team detected another planet in the fray — GJ433D. However, despite being the size of Neptune, it’s a little too far from its star to be the right temperature. Scientists believe that its surface water is probably frozen.

“GJ 433 d is the nearest, widest, and coldest Neptune-like planet ever detected,” said Fabo Feng, co-author of the study.

See also:
Habitable earth-sized planet discovered but its Sun doesn't set for over two weeks

NASA's planet-hunter uncovers its first world with two stars 1,300 light-years away

Scavenger hunt for Planet X just dropped another clue