While these planets are 40 lightyears away, LHS 1140b is a negligible one lightyear closer.
Now, however, for at least some of the astrobiological gambling community, the odds have changed, perhaps dramatically, following the announcement of a newly discovered exoplanet orbiting a red dwarf star some 39 light years from Earth.
When red dwarf stars are young, they are known to emit radiation that can be damaging for the atmospheres of the planets that orbit them.
In this case, the planet's large size and closeness to its sun means that a magma ocean could have existed on its surface for millions of years, which fed steam into the atmosphere, replenishing the planet with water.
A planet's atmosphere is what we need to be studying the most if/when we're looking for signs of life.
'The LHS 1140 system might prove to be an even more important target for the future characterisation of planets in the habitable zone than Proxima b or TRAPPIST-1, ' two members of the global team, Drs Xavier Delfosse and Xavier Bonfils, said. "This has been a remarkable year for exoplanet discoveries!".
LHS 1140b's dense metal core, however, might mean that it was covered by an ocean of magma during its host star's insane youthful period. That means in the next several years, new telescopes can spy its atmosphere in a targeted search for signs of life.
An artist's impression of "rocky super-Earth" LHS 1140b and its red dwarf host star.
As LHS 1140 is much smaller and cooler than our own star, it doesn't throw out anything close to the levels of radiation that our Sun is capable of emitting.
It has likely retained most of its atmosphere and passes in front of its parent star as it orbits, blocking a little of its light every 25 days.
The centre's lead author Jason Dittmann said it was the most exciting discovery of an exoplanet - a planet that orbits a star other than the Sun - in a decade.
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The ships are now operating in the Indian Ocean, conducting exercises with Australian naval forces, according to Defense News. The team is expected to fly out of Seoul, South Korea on Friday. "North Korea has referred to me as the lesser evil".
The discovery is quite unique because LHS 1140 is a small cool star, not as active energetically as other stars which other exoplanets have been found to orbit. And a good chunk of them also lie in the habitable zone.
A new, nearby exoplanet could be just the boilerplate needed to find out if life could exist in untold numbers of star systems.
The boundaries of the habitable zone are critical.
It's the fifth such life-possible planet outside our solar system revealed in less than a year. Life would also be unsustainable if it's too thin and wispy like Mars, with all the water locked up as ice. Such rocky worlds seem a better bet for hosting life than do the puffy gas planets orbiting other stars.
The fact that LHS 1140b is a super-Earth is a bit concerning to any hopes that - if humans ever manage to master interstellar travel - we could one day settle the planet and establish a colony.
This rookie, known as LHS 1140b, hails from the constellation Cetus (the sea monster).
The new planet was found using eight small telescopes in Chile and help from an amateur planet-hunter, according to Charbonneau.
The MEarth-South telescope array.
The discovery was first made with the MEarth facility, in Arizona, which detected the dips in light as the exoplanet passed in front of its star. The orbit is seen nearly edge-on from Earth and as it passes in front of its star, every 25 days, it blocks a portion of the star's light. A planet's gravitational pull can cause its host star to slightly wobble, giving astronomers an idea of just how massive the world is.
Astronomers will now use the Hubble Space Telescope to try to work out how much life-destroying radiation is currently being showered upon LHS 1140b.
"Right now we're just making educated guesses about the content of this planet's atmosphere", Dittmann said.
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