NASA retires planet-searching Kepler mission
By Amanda Jermyn



In 2009 NASA’s Kepler spacecraft was launched to search for planets outside our solar system. Its space telescope scanned a small patch of our Milky Way galaxy for stars that experience dips in brightness, the result of one or more planets passing in front of them. Since its launch Kepler has observed more than 530,000 stars, detected just under 6,000 possible planets, and discovered over 2,600 confirmed planets orbiting other stars. We can infer from Kepler’s data that our galaxy alone should contain billions of planets, of which about 10 billion could potentially be habitable, and we now know that there are far more planets than there are stars. We’ve come a long way since the first exoplanet was discovered a mere 30 years ago.

Now NASA’s first planet-hunting mission is being retired because it has run out of fuel for conducting scientific observations. It will, however, continue to drift through space in a safe orbit around the sun. While it is sad when any mission comes to an end Kepler’s extraordinary discoveries are cause for celebration.

Thanks to Kepler we now know that our own galaxy contains a dazzling array of planets, including water worlds and planets with multiple suns. This mission has also shown us that planetary systems can look very different from our own, in some cases with many planets orbiting very close to their host star.

Recent analysis of Kepler’s discoveries indicates that between 20 and 50 percent of stars are likely to have small, possibly rocky planets about the size of Earth located within the habitable zone of their host stars. This means these planets would be located at just the right distance from their star where temperatures allow for water to exist in liquid form. And liquid water is a presumed requirement for life as we know it.

Natalie Batalha, a Kepler mission scientist now at the University of California, Santa Cruz, noted that “the search for planets is the search for life. These results will form the basis for future searches for life.”

According to Jessie Dotson, Kepler’s project scientist at NASA’s Ames Research Center in California, the mission’s retirement isn’t the end of its revelations. There are still discoveries to be made from the existing data, and future missions will be able to build on Kepler’s discoveries.

One such mission is NASA’s new planet hunter, the Transiting Exoplanet Survey Satellite, or TESS, which launched in April. In addition, giant space and ground-based telescopes are being developed to detect and observe exoplanets.

A space telescope currently under development, the Wide Field Infrared Survey Telescope, or WFIRST, has advanced optics that will allow it to directly detect non-transiting Jupiter-type planets around nearby stars. It should also be able to survey exoplanets with long orbital periods by detecting the gravitational lenses those planets form as they pass in front of background stars. What this means is that the gravitational force exerted by the planet bends the light from the background stars, and it is this distortion of light that allows you to detect the planet. Detecting planets with long orbital periods is otherwise difficult using the transiting method because there could be a very long wait until the next time the planet passes in front of its star.

The Kepler mission has far exceeded expectations and has paved the way for new planet-hunting missions. Isaac Newton once said: “If I have seen further than others, it is by standing upon the shoulders of giants.” Planet hunters of the future will see further by standing on the shoulders of Kepler.

While there is no public Stars Club meeting in December, on Friday, January 4th at 7:30pm, the Stars Club and the Springfield Science Museum will host “Stars over Springfield,” an astronomy adventure for the whole family. Richard Sanderson, retired curator of physical science at the Springfield Science Museum, will give a talk on the upcoming January 21st lunar eclipse and other eclipses. A fee of $3 for adults and $2 for children under 18 will be charged.