Just when you started to wrap your mind around the vastness of the cosmos, NASA has announced a new collection of exoplanets found by their dutiful Kepler Space Telescope's data set. On Monday, astronomers declared the discovery of 1,284 official new exoplanets from Kepler's candidate list, bringing the Earth-trailing observatory's heavenly total to 2,325 confirmed alien worlds, yet none a perfect clone of our Earth.
"We don't necessarily have an exact dead ringer for a planet like Earth, in terms of its orbit and size," said Kepler mission scientist Natalie Batalha, of NASA's Ames Research Center. "Two of the newly announced worlds — Kepler-1638b and Kepler-1229b — are among the most Earth-like planets yet discovered."
Kepler-1638b orbits a star very similar to the sun, but the planet is about 60 percent wider than our Earth. Kepler-1229b is nearly the exact size as Earth, but that far-off world orbits a cold red dwarf, a star significantly smaller and chillier than the sun.
Hunting down Earth-like planets around the habitable zone is top priority for the $600 million Kepler observatory project, which launched in March of 2009. By looking for minute brightness dips across star faces while eyeing 150,000 suns, scientists can extrapolate the location of strange newfound worlds. Since a mishap in 2013 that disabled Kepler's ultraprecise pointing ability, its range and scope have been greatly diminished for its K2 mission phase starting in 2014. The spacecraft's lessened parameters now include a broadened observation scope to also search for supernova explosions, asteroids, comets, pulsars and other celestial spectacles.
"The most eagerly anticipated such extrapolation is eta-Earth. Kepler observations analyzed to date suggest that this figure is about 25 percent, meaning that one-quarter of the 70 billion or so "normal" (main-sequence) stars in the galaxy appear to host rocky planets in their habitable zones," Batalha said.
Since 1992, when astronomers initially spied the first world beyond our solar system, a total of 3,200 exoplanets have been revealed out in the infinite darkness. The Kepler team will continue to download the spacecraft's massive data set and provide validation work through at least October 2017, when the original mission finalizes and NASA's Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope (JWST) are expected to launch in 2017 and 2018.
"Right now, I think that everything is looking good with the spacecraft," said Kepler/K2 mission manager Charlie Sobeck during Monday's news conference. "The two remaining [reaction] wheels look to be excellent. They're in good health. So the K2 mission is ultimately going to be constrained by fuel. And right now, my estimate is going to be something over two more years' worth of fuel. So, sometime [in the] middle of summer of 2018 is when I think that we may run out."