‘Little spacecraft that could’ retires after nine years
During its nine-year mission, NASA’s revolutionary Kepler space telescope Kepler found more than 2,600 planets orbiting stars outside the solar system — including many with the potential for harbouring life.
Thanks to the spacecraft, scientists have learned that the Milky Way Galaxy has more planets than stars.
“Before we launched Kepler, we didn’t know if planets were common or rare,” said Paul Hertz, director of the National Aeronautics and Space Administration’s astrophysics division in Washington, D.C.
So it was with mixed feelings that the U.S. space agency announced this week that the space telescope has run out of fuel and will be retired.
Scientists have poured over Kepler’s data and concluded that between 20 and 50 per cent of the stars we can see are accompanied by planets that have much in common with Earth.
These planets are about the same size as ours and orbit at a distance where any water that might be on the surface would be stable in liquid form.
Even more common is a type of planet that is missing from our own solar system — so-called super-Earths that are larger than our planet but smaller than Neptune.
Kepler has also revealed that many solar systems are far more crowded than our own. One of its most tantalizing discoveries was the TRAPPIST-1 planetary system, home to seven rocky Earth-sized worlds a mere 39 light-years away. All seven of these planets are closer to their star than Mercury is to the sun.
Kepler has overcome mechanical difficulties in the past. But without the fuel needed to conduct further science operations, NASA opted to end the mission.
“I thought of it as the little spacecraft that could,” said Jessie Dotson, a Kepler project scientist at NASA’s Ames Research Center in Mountain View, Calif.
“It always did everything we asked for, and sometimes more.”
The space telescope will remain in its current orbit, which is a safe distance from Earth, officials said. Though Kepler is retiring, NASA will continue its search for planets outside the solar system.
In April, the space agency launched the Transiting Exoplanet Survey Satellite, or TESS, to look for planets around 200,000 nearby stars. Future missions, such as the James Webb Space Telescope, will further investigate these planets to see if there are any indications of life.