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Not too long ago, Venus was discovered to have a twin sister in an exoplanet orbiting a distant star. Now Earth has its own.
Both doppelgangers orbit the same star. The red dwarf could possibly host even more planets, since NASA’s Kepler space telescope (RIP) missed Earth’s twin the first time around (hey, even ultra-powerful telescopes make mistakes). Now a group of scientists have discovered that not only is the planet Kepler-1649c close to Earth in terms of size, temperature, and location in the habitable zone of its star, but it's one of the most similar planets to Earth ever found.
"What gets us excited is that red dwarf stars are the most common star type in the galaxy, meaning planets of this size and temperature could be more common than we previously thought. And that is exciting news for the search for life in the galaxy," astrophysicist Jeff Coughlin of the SETI Institute, director of NASA's K2 program, tells SYFY WIRE. He and his colleagues recently published a study on the find in Nature Astronomy.
Kepler initially messed up because there is a pretty wide margin for error when an instrument is programmed to search for planets using the transit method. It keeps its telescopic eye on the star and watches out for any shadows obscuring that star. Unfortunately, just about anything floating through space, such as a comet or asteroid, could transit in front of a star. Even fluctuations in the star’s brightness could be deceptive. Kepler’s Robovetter algorithm was supposed to sort through every instance of a star dimming to find which ones were just false positive and which ones betrayed actual planets. Turned out what Robovetter thought was a false positive was actually an exoplanet.
Because astronomers already assumed that the robot was imperfect — more proof that AI is still no replacement for the human brain (yet) — the Kepler False Positive Working Group exists to wade through the overflow of Kepler data that is still being investigated despite the telescope breathing its last in 2018.
Kepler-1649c is eerily close to Earth in size and likely temperature. Those are all the similarities that can be made out for sure right now, according to Coughlin. The fact that it orbits a red dwarf only a quarter the size of our Sun could mean that it is tidally locked much in the same way the Moon is tidally locked to Earth. Tidal locking happens when distortions in gravity cause a cosmic object and the star or other body it is orbiting to rotate at the exact same time. One side of a cosmic object will face the star or other object, so that side will always have light shining down on it while the other is forever plunged into darkness.
“That means one side could be very hot, and the other side very cold, but that also depends on whether it has an atmosphere or not, and that's something we just don't know yet,” says Coughlin. “Also, it's very close to its star — it's ‘year,’ or the amount of time it takes to orbit the star, is only 19.5 Earth days long!”
Most of us probably wouldn’t want to know our age in Kepler-1649c years.
So what is the possibility of this planet crawling with bizarre life forms? We can only go off of what we know from life as we know it on Earth. We’re already in the habitable zone of the Sun, just as Kepler-1649c is in the habitable zone of its star, so it’s got that going for it. Its size and temperature were estimated through how much the light and heat streams in. Those conditions are not just close to what Earthlings can flourish in, but can also support liquid water without it either freezing or vaporizing right away. Maybe there are things out there that live on what would be poison to us, but until we can prove it, this is all we’ve got.
“As far as speculating on possible life, the data we got from Kepler about this planet only gave us some few, enticing details,” says Coughlin. “But we just don't have enough information to know if life is there or not. This type of star is known for flare-ups that may make a planet's environment challenging for life.”
Of course, there might be another planet hiding from us in Kepler-1649c’s orbit, so hold on.