Add another 95 exoplanets to the total tally discovered by NASA’s Kepler spacecraft. One of them orbits the brightest star, HD 212657, confirmed to have a planet around it. Andrew Mayo, the main author in the study presented in the Astronomical Journal, points out this exoplanet will make a great target for ground-based observatories.
How do you spot a planet far from Earth? Researchers look for small dips in brightness around stars. But these dips don’t automatically mean a planet is there. “We found that some of the signals were caused by multiple star systems or noise from the spacecraft. But we also detected planets that range from sub Earth-sized to the size of Jupiter and larger,” said Mayo.
A lot of the time, the planets they do find have extraordinarily short orbital periods. That planet around HD 212657 circles its star in just 10 days. To put that in perspective, Mercury (closest planet to the Sun), completes a trip around the Sun in 88 days.
These planets aren’t the best candidates for life (extremely short orbits like this almost guarantee they are tidally locked), but they are easier to spot. It’s much easier to wait a few days for the brightness dip to happen again, then wait months or years for that same planet to pass in front of its host star.
But even lifeless rocks and huge gas giants will help researchers understand how planetary systems form and evolve and “allow us to place our own solar system into a galactic context,” says Mayo.
A new satellite will soon join the hunt
All eyes are focused on next year’s launch of the James Webb Space Telescope (JWST), but another planet-hunting satellite will start searching much sooner.
The Transiting Exoplanet Survey Satellite (TESS) is scheduled for a Spring launch and will search about 90% of the sky during its mission. It will monitor the brightness of more than 200,000 stars during its two-year mission in the hopes of finding rocky exoplanets at just the right distance from its stars. Not too hot to boil all surface water away, and not too cold to turn the planet into a chunk of ice.
Researchers working with TESS hope to find more than 1,500 transiting exoplanet candidates, About 500 of which will hopefully be classified as Earth-sized and Super-Earth (planets with radii less than twice that of Earth). The best candidates spotted by TESS will be passed on the JWST, and other observatories for follow up observations.
A SpaceX Falcon 9 will send the planet-hunting TESS above Earth sometime between March and June.