A comparison of Earth and Kepler-1649c, an exoplanet only 1.06 times Earth's radius.
NASA/AMES RESEARCH CENTER/DANIEL RUTTER
Does liquid water exist on the surface of Kepler-1649c, a rocky alien planet just 6% bigger than the Earth?
A new paper published in the Astrophysical Journal Letters reveals that astronomers have found a new world around a distant star that’s almost the same size as Earth—and it orbits in its star’s “habitable zone.”
Kepler-1649c is also now the most similar exoplanet yet found to Earth in terms of both size and temperature.
The data came from the now defunct Kepler/K2 space telescope that observed nearly 200,000 stars for four years. Its mission was to calculate what fraction of stars in the Milky Way have Earth-size planets in their habitable zone. The mission was finally ended in 2018 after a few years of technical problems, but this data comes from pre-2013.
So far, 4,144 exoplanets have been discovered using data from Kepler.
“In terms of size and likely temperature, this is the most similar planet to Earth that has ever been found with Kepler,” said co-author Jeff Coughlin at the SETI Institute. “It's incredible to me that we just found it now, seven years after data collection stopped on the original Kepler field.”
What is an exoplanet?
Whether they’re called exoplanets, extrasolar planets, or simply planets, these objects are planets that orbit around stars other than our Sun. By definition that means they are not in the solar system, and therefore very, very far away. As such, they’re mostly too far away to be directly imaged. Instead, they’re found using data that infers their existence, mostly by observing the effect of orbiting planets on the host star—such as a slight dimming in starlight as a planet transits across it, or tiny effect on the stars movements.
Where and what is Kepler-1649c?
The new world is 302 light-years away in the constellation of Cygnus. It orbits an orbits a M-type star that’s not visible from Earth, called Kepler-1649. An M-type star is a low-mass star also known as a “red dwarf,” which are by far the most common stars found in the Milky Way. While the star it orbits is much smaller than our Sun, it gets about 75% of the sunlight Earth does. Kepler-1649 c is 1.06 times the size of Earth and orbits its star every 19.5 days, according to the new paper.
How was Kepler-1649c discovered?
It was originally classified as a false positive by computers, but was found by visual inspection of the data. “Out of all the mislabeled planets we've recovered, this one's particularly exciting,” said Andrew Vanderburg, lead author and a NASA Sagan Postdoctoral Fellow at the University of Texas at Austin. “If we hadn't looked over the algorithm's work by hand, we would have missed it.”
Whether they’re called exoplanets, extrasolar planets, or simply planets, these objects are planets that orbit around stars other than our Sun. By definition that means they are not in the solar system, and therefore very, very far away. As such, they’re mostly too far away to be directly imaged. Instead, they’re found using data that infers their existence, mostly by observing the effect of orbiting planets on the host star—such as a slight dimming in starlight as a planet transits across it, or tiny effect on the stars movements.
Where and what is Kepler-1649c?
The new world is 302 light-years away in the constellation of Cygnus. It orbits an orbits a M-type star that’s not visible from Earth, called Kepler-1649. An M-type star is a low-mass star also known as a “red dwarf,” which are by far the most common stars found in the Milky Way. While the star it orbits is much smaller than our Sun, it gets about 75% of the sunlight Earth does. Kepler-1649 c is 1.06 times the size of Earth and orbits its star every 19.5 days, according to the new paper.
How was Kepler-1649c discovered?
It was originally classified as a false positive by computers, but was found by visual inspection of the data. “Out of all the mislabeled planets we've recovered, this one's particularly exciting,” said Andrew Vanderburg, lead author and a NASA Sagan Postdoctoral Fellow at the University of Texas at Austin. “If we hadn't looked over the algorithm's work by hand, we would have missed it.”
While there are other exoplanets closer to Earth in size (such as TRAPPIST-1f and perhaps Teegarden c) and temperature (TRAPPIST-1d and TOI 700d), there is no other exoplanet that is considered to be closer to Earth in both of these values that also lies in the habitable zone of its system.
The authors also argue that the identification of Kepler-1649c hints that terrestrial planets around M-dwarfs may be more common than those around more massive stars.
“The more data we get, the more signs we see pointing to the notion that potentially habitable and Earth-sized exoplanets are common around these kinds of stars,” said Vanderburg. “With red dwarf stars almost everywhere around our galaxy, and these small, potentially habitable and rocky planets around them too, the chance one of them isn’t too different than our Earth looks a bit brighter.”
"This intriguing, distant world gives us even greater hope that a second Earth lies among the stars, waiting to be found," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate in Washington. "The data gathered by missions like Kepler and our Transiting Exoplanet Survey Satellite [TESS] will continue to yield amazing discoveries as the science community refines its abilities to look for promising planets year after year."
Could there be life on Kepler-1649c?
Red dwarf stars are known for having one deadly characteristic; they can occasionally flare, something that would drape any orbiting planets in enough radiation to make life very unlikely.
Are there any other planets orbiting Kepler-1649?
Yes—it shares its sun with a planet much like Venus. Discovered in 2017, Kepler-1649 b is a “super Earth” with a mass of 1.28 Earths that takes 8.7 days to complete one orbit of its star from 0.0514 AU out. A paper in 2017 compared Kepler-1649 b to Venus, stating that is was a “Venus analog candidate” with a similar climate.
So Kepler-1649c is of huge interest to astronomers not just because it’s in the habitable zone and Earth-size, but because of how it might interact with this neighboring planet.
The authors also argue that the identification of Kepler-1649c hints that terrestrial planets around M-dwarfs may be more common than those around more massive stars.
"This intriguing, distant world gives us even greater hope that a second Earth lies among the stars, waiting to be found," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate in Washington. "The data gathered by missions like Kepler and our Transiting Exoplanet Survey Satellite [TESS] will continue to yield amazing discoveries as the science community refines its abilities to look for promising planets year after year."
Could there be life on Kepler-1649c?
Red dwarf stars are known for having one deadly characteristic; they can occasionally flare, something that would drape any orbiting planets in enough radiation to make life very unlikely.
Are there any other planets orbiting Kepler-1649?
Yes—it shares its sun with a planet much like Venus. Discovered in 2017, Kepler-1649 b is a “super Earth” with a mass of 1.28 Earths that takes 8.7 days to complete one orbit of its star from 0.0514 AU out. A paper in 2017 compared Kepler-1649 b to Venus, stating that is was a “Venus analog candidate” with a similar climate.
So Kepler-1649c is of huge interest to astronomers not just because it’s in the habitable zone and Earth-size, but because of how it might interact with this neighboring planet.
Can astronomers further study Kepler-1649c?
Yes—Kepler-1649c’s atmosphere is not known, which could affect its temperature. Even the planet's size has a margin of error.
The James Webb Space Telescope (JWST) has the potential to probe the atmospheres of intriguing exoplanets like Kepler-1649 b and Kepler-1649 c to see if they really could host life.
Wishing you clear skies and wide eyes.
Yes—Kepler-1649c’s atmosphere is not known, which could affect its temperature. Even the planet's size has a margin of error.
The James Webb Space Telescope (JWST) has the potential to probe the atmospheres of intriguing exoplanets like Kepler-1649 b and Kepler-1649 c to see if they really could host life.
Wishing you clear skies and wide eyes.
