Kepler was a retired space telescope launched by NASA whose mission was to seek signs of other Earth-like planets. “NASA’s elite planet-hunting spacecraft” is what it was commonly known as. It was launched on March 7, 2009, as part of humanity’s quest to find life beyond Earth. During its nine-plus years of service, this sun-orbiting space telescope observed a massive 530,506 stars, and detected a total of 2,682 confirmed exoplanets, accounting for 70% of all alien worlds known to humanity. It was named after the astronomer Johannes Kepler, with the principal investigator being William J. Borucki. Post its nine years of operation, the telescope’s reaction control system fuel was exhausted, and NASA announced its retirement on October 30, 2018. The Kepler telescope was formerly set to launch in 2006, but it was destined to being pushed back to 2009 as the spacecraft design and development proceeded and the Discovery program had to undergo like the loss of the CONTOUR spacecraft and budget difficulties. While Kepler’s development persisted, exoplanet discovery methods and technologies enhanced and the exoplanet count at the time of Kepler’s launch in March 2009 was up to 300, with some Neptune-sized planets being discovered.
Kepler’s sole scientific instrument is a photometer that continually monitored the brightness of approximately 150,000 main sequence stars in a fixed field of view. These data are passed on to Earth and then examined to detect periodic dimming caused by exoplanets that cross in front of their host star. Our home planet which is the Earth flares up like a cosmic lighthouse in a photo taken by NASA’s Kepler space telescope, which has discovered more than 2,500 alien worlds to date. NASA’s official wrote in a description that it was captured on December 10, 2017, after the spacecraft adjusted its telescope to a new field of view, Earth’s reflection as it slipped past was so extraordinarily bright that it created a saber-like saturation bleed across the instrument’s sensors, obscuring the neighboring moon. This was released Wednesday (March 7)—the ninth anniversary of Kepler’s launch.
Earth seems so bright because Kepler’s light-sensing photometer is extremely sensitive. The instrument was designed to sense the tiny brightness dips caused when exoplanets cross their host stars’ faces from Kepler’s perspective. The spacecraft first performed this work while staring at about 150,000 stars simultaneously. But this initial mission came to a halt in May 2013, when the second of Kepler’s four orientation-maintaining reaction wheels failed to perform, restricting the telescope of its precision pointing capability. Mission managers soon found out a way to stabilize Kepler using sunlight pressure, however, and Kepler had embarked on a new mission called K2. During K2, Kepler continues to hunt for planets on a more limited basis, and it’s also observing a variety of other celestial objects and phenomena.
The Kepler spacecraft terminated its 9-year mission as the highly successful mission which can enable humanity to look back at an instrument that greatly expanded our knowledge of planetary systems around other stars and also discovered many Earth-sized and smaller planets, where some of them in the habitable zone where liquid water, and therefore life as we know it, could exist. The Kepler mission was drawn up as a Discovery Program mission at the turn of the century and was approved as the tenth mission in the program in December 2001. During that time only 80 exoplanets had been discovered since Gamma Cephei Ab was first found in 1989 (but confirmed in 2002), and the exoplanets were being discovered with the available technology at that time were large “hot Jupiter” gas giants orbiting close to their stars, extremely unsuitable for life as we know it.
Kepler had been running low on fuel for months after already well past its expected lifetime. Its ability to point at distant stars and identify possible alien worlds deteriorated dramatically at the beginning of October, but flight controllers still managed to get its latest observations. The telescope has now exhausted its ability, its fuel tank empty. Almost lost in 2013 because of equipment failure, Kepler was abandoned by engineers and chose to prefer into the cosmos, thick with stars and galaxies, ever on the lookout for dips in the brightness of stars that could indicate an orbiting planet. K2 was the resurrected mission and yielded 350 confirmed exoplanets, or planets orbiting other stars, on top of what the telescope had already uncovered since its March 7, 2009, launch from Cape Canaveral. In all, close to 4,000 exoplanets have been confirmed and identified over the past two decades, two-thirds of them thanks to Kepler.
Kepler kept its focus on stars thousands of light-years away and, according to NASA, proved that statistically there’s at least one planet around every star in our Milky Way Galaxy.
The Kepler spacecraft, though it has now passed into history, has carved its niche as one of the highly successful space science missions ever, and its discoveries will be an important part of astronomy from now on.
(Source- NASA spacelight.com)