Scientists have confirmed 104 planets outside our solar system – so-called exoplanets – discovered by the Kepler telescope.
The list was drawn up from 197 candidates found by Kepler during its K2 mission.
The new discoveries include a system comprising four possibly rocky planets that could potentially harbour life, according to lead author Ian Crossfield of the University of Arizona.
They are all larger than Earth and orbit the M dwarf star K2-72, 181 light-years away in the direction of the Aquarius constellation.
While all the planets are in tight orbits, closer than Mercury’s around our sun, the dwarf is both smaller and dimmer than the sun. That suggest two of the planets might enjoy similar levels of radiation to the Earth.
The planets orbit their star in anything from five and a half to 24 Earth days.
Kepler identifies candidates by measuring the dip in a star’s brightness when a planet passes in front of it. All Kepler’s discoveries were followed up with observations by earth-based telescopes before being confirmed.
The telescope, which suffered a crippling equipment failure in 2013, was given a new lease on life with an innovative fix by NASA.
After that, the craft’s mission was renamed the K2 mission, tasked with studying an ecliptic field of view.
The K2 mission is capable of observing a larger fraction of cooler, smaller, red-dwarf type stars, than the first mission. These stars have more common in the Milky Way than sun-like stars.
“An analogy would be to say that Kepler performed a demographic study, while the K2 mission focuses on the bright and nearby stars with different types of planets,” Crossfield was quoted as saying.
“The K2 mission allows us to increase the number of small, red stars by a factor of 20, significantly increasing the number of astronomical ‘movie stars’ that make the best systems for further study.”
To validate candidate planets researchers use high-resolution images of the planet-hosting stars and high-resolution optical spectroscopy. By dispersing the starlight, the resulting the spectrographs allow the researchers to infer the physical properties of a star such as mass, radius and temperature.
“This bountiful list of validated exoplanets from the K2 mission highlights the fact that the targeted examination of bright stars and nearby stars along the ecliptic is providing many interesting new planets,” said Steve Howell, project scientist for the K2 mission at NASA’s Ames Research Center in California.
“These targets allow the astronomical community ease of follow-up and characterisation, providing a few gems for first study by the James Webb Space Telescope, which could perhaps tell us about the planets’ atmospheres.”