NASA’s Kepler Space Telescope, in its last observing campaign, made a significant discovery before running out of fuel. Due to mechanical issues, the spacecraft could only gather valuable observations for about a week, out of its month-long final mission. Despite the challenges, a collaborative effort between astrophysicists, citizen scientists, and professional astronomers led to the identification of three exoplanets in the limited dataset.
Throughout its nearly decade-long mission, Kepler diligently surveyed hundreds of thousands of stars, contributing to the confirmation of over 2,600 exoplanets. Notably, it became the first NASA mission to spot an Earth-size planet within the habitable zone of its host star, where liquid water could potentially exist on the planet’s surface.
The recent discovery showcases the tenacity of Kepler, even in its final days. The three exoplanets found are considered to be of average size, falling between Earth and Neptune in size. They orbit their respective stars closely.
Elyse Incha, a senior at the University of Wisconsin-Madison, expressed excitement about these exoplanets, emphasizing that they were observed during the last days of Kepler’s operations. This achievement demonstrates Kepler’s exceptional planet-hunting capabilities throughout its operational lifespan.
The findings of the exoplanet trio, led by Incha and her team, were published in the May 30, 2023 issue of the Monthly Notices of the Royal Astronomical Society.
Launched in March 2009, Kepler initially aimed to monitor a specific patch of sky in the constellations Cygnus and Lyra continuously. This long-term observation allowed the telescope to detect changes in the brightness of stars caused by transiting planets.
Although Kepler faced mechanical setbacks in 2014, the mission team successfully devised a solution, enabling the telescope to continue its operations under the new campaign called K2. For another four years, Kepler surveyed over half a million stars, expanding the exoplanet catalog.
When Kepler was retired in October 2018, its legacy comprised over 2,600 confirmed exoplanets, making it an instrumental tool in exoplanet research.
The final K2 campaign, lasting only a month, was cut short due to fuel constraints. Despite the limited dataset, Incha and her team, in collaboration with the Visual Survey Group, a collective effort between citizen scientists and professional astronomers, meticulously analyzed the available data. The citizen scientists, using visual surveys, played a crucial role in detecting patterns in the light curves, which automated searches often miss.
The result of their combined efforts led to the identification of one transit for each of the three planet candidates, with each planet orbiting a different star.
After the initial discovery, Incha’s team examined the lower-quality data from the remaining portion of the campaign and found additional transits for two of the flagged stars from the visual search, further confirming their existence.
The planets identified were named K2-416 b, K2-417 b, and EPIC 246251988 b. K2-416 b is approximately 2.6 times the size of Earth and orbits a red dwarf star every 13 days. K2-417 b, slightly larger than three times Earth’s size, also orbits a red dwarf star, but completes an orbit every 6.5 days. EPIC 246251988 b, the largest among the trio, is nearly four times Earth’s size and orbits a Sun-like star in approximately 10 days.
To add to the significance of the discovery, NASA’s Transiting Exoplanet Survey Satellite (TESS) also observed the same patch of space containing these three exoplanets during August and September 2021. This allowed astronomers to detect additional potential transits for K2-417 b.
Kepler’s retirement in 2018 marked the end of an era, as NASA’s Transiting Exoplanet Survey Satellite (TESS) took over the planet-hunting mission. TESS continues to build upon Kepler’s dataset, offering new insights into its discoveries.
The findings from Kepler’s last planet discoveries were detailed in a scientific paper published in the Monthly Notices of the Royal Astronomical Society on May 30, 2023.
The Kepler and K2 missions were managed by NASA’s Ames Research Center in California’s Silicon Valley for NASA’s Science Mission Directorate. Kepler’s development was overseen by NASA’s Jet Propulsion Laboratory in Pasadena, California, while Ball Aerospace & Technologies Corporation in Boulder, Colorado, operated the spacecraft with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.
TESS, a NASA Astrophysics Explorer mission, is led and operated by MIT, managed by Goddard, and involves collaboration with various partners across academia and research institutes worldwide.
