Astronomers Discover the Last Three Planets the Kepler Telescope Observed Before Going Dark

The Kepler Space Telescope, launched by NASA in 2009, has played a pivotal role in the discovery of exoplanets. Out of the 5,000 confirmed planets beyond our solar system, more than half were discovered by this resilient observatory. 

Kepler exceeded its original mission duration and continued observing the skies for over nine and a half years, detecting potential planets by monitoring periodic dips in starlight.

An illustration of various worlds discovered by Kepler. (Image Credit: NASA).

The Last Glimpse: Kepler’s Final Days and the Search for Last Planets

As the Kepler telescope approached the end of its operational life, it continued recording the brightness of stars despite depleting fuel. On October 30, 2018, after running out of fuel, the spacecraft was officially retired. 

Now, astronomers from MIT and the University of Wisconsin at Madison, in collaboration with citizen scientists, have embarked on a search for the last planets observed by Kepler before its retirement.

Planet Candidates Unveiled: Uncovering Three Stars with Brief Dimming

The team meticulously analyzed the telescope’s final week of high-quality data and identified three stars in the same region of the sky that exhibited brief dimming. Through their investigation, they determined that two of the stars host validated planets, while the third star harbors a planet candidate awaiting further verification.

Validated Planets: Introducing K2-416 b and K2-417 b

Among the discoveries, two planets have been validated. K2-416 b, approximately 2.6 times the size of Earth, orbits its star every 13 days. K2-417 b, slightly larger at just over three times the size of Earth, completes an orbit around its star every 6.5 days. These planets, known as “hot mini-Neptunes,” reside approximately 400 light years away from Earth.

EPIC 246251988 b: The Neptune-sized Planet Candidate

The third discovery, EPIC 246251988 b, is the largest of the three worlds, nearly four times the size of Earth. This Neptune-sized planet candidate orbits its star in approximately 10 days and is located approximately 1,200 light years away from Earth.

Significance and Historical Importance: Last Discoveries by Kepler

The detection of these planets holds historical importance as they are likely the last ever discovered by Kepler. Although the planets themselves are not particularly unusual, the circumstances surrounding their discovery make them intriguing and noteworthy.

Data Squeeze: Utilizing the Short Dataset to the Fullest

Despite limited available data, the team aimed to extract as much valuable information as possible from Kepler’s final observations. The dataset consisted of only a week of high-quality observations and another 10 days of noisier measurements due to the spacecraft rapidly depleting fuel.

By Eye: Collaboration with Citizen Scientists in the Visual Survey Group

To sift through the data effectively, the astronomers sought the assistance of the Visual Survey Group, a team of amateur and professional astronomers specializing in exoplanet searches. 

Their expertise in identifying characteristic dips in brightness, indicative of planetary transits, proved invaluable, particularly in analyzing the short dataset from Kepler’s last campaign.

Spotting Additional Transits: Analyzing Lower-Quality Observations

The team focused on specific regions of the light curves between thruster activity in Kepler’s lower-quality observations. Despite the spacecraft’s drift caused by erratic thruster firing, the astronomers identified a second transit for K2-416 b and K2-417 b, solidifying the existence of these planets. Furthermore, data from NASA’s Transiting Exoplanet Survey Satellite (TESS) helped confirm the planet candidate around K2-417 b.

Confirmation and Follow-up: Validating the Existence of Planets

The researchers conducted follow-up observations, including ground-based observations, to eliminate potential false positives and confirm the existence of the discovered planets. These thorough investigations ruled out interference from background stars and close-in stellar binaries.

Ensuring No Data Goes to Waste: Kepler’s Invaluable Contribution

The discovery of these last planets observed by Kepler underscores the immense value of the telescope’s data. Astronomers strive to extract every ounce of knowledge from the vast treasure trove of observations, knowing that there are still countless discoveries waiting to be made.

FAQ About the Last Three Planets the Kepler Telescope Observed:

Q: How many planets were discovered by NASA’s Kepler Space Telescope?

A: More than half of the confirmed exoplanets (over 2,500) were discovered by NASA’s Kepler Space Telescope.

Q: When was the Kepler Space Telescope retired?

A: The Kepler Space Telescope was officially retired on October 30, 2018.

Q: What are the sizes and orbital periods of the validated planets discovered in Kepler’s last days?

A: K2-416 b is about 2.6 times the size of Earth and orbits its star every 13 days, while K2-417 b is slightly larger than Earth and has an orbital period of 6.5 days.

Q: How far away are the validated planets from Earth?

A: The validated planets, K2-416 b and K2-417 b, are located approximately 400 light years away from Earth.

Q: What is the size and distance of the planet candidate EPIC 246251988 b?

A: EPIC 246251988 b is almost four times the size of Earth and is situated approximately 1,200 light years from Earth.

Q: How did astronomers analyze the last data collected by Kepler?

A: Astronomers collaborated with citizen scientists to visually examine the light curves of thousands of stars, searching for characteristic dips in brightness.

Q: How did the team validate the existence of the planets?

A: The team conducted follow-up observations, including ground-based observations, to rule out false positive scenarios and confirm the existence of the discovered planets.

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