Katherine Xiu

A Yale graduate student working in collaboration with a Yale professor and a researcher at NASA’s Ames Research Center recently discovered a previously overlooked planet 3,000 light years from Earth.

Joseph Schmitt GRD ’18 was the lead author of a study published in The Astronomical Journal on March 28 that described the discovery of this new planet, dubbed Kepler-150 f. The data, which came from the Kepler Mission — a NASA project that searches for Earth-sized planets — had been studied previously, but Kepler-150 f had been overlooked. Under the advice of Yale astronomy professor Debra Fischer and in partnership with NASA’s Jon Jenkins, Schmitt discovered the planet by combing through the Kepler Mission’s digital data by eye and removing data from previously known planets.

“I looked at all of the stars that had three or more planets by eye,” Schmitt said. “And this was the only one I found that was brand new.”

The planet is similar in size to Neptune and takes 637 days to circle its host star, which is orbited by four other known planets.

According to the study, the Kepler Mission has discovered more than 4,700 “Kepler Objects of Interest” that are classified as either confirmed planets or planet candidates. Schmitt explained that the Kepler telescope has been pointed at around 190,000 stars for four straight years.

The Kepler Mission detects planets by measuring the brightness of stars over time. When a planet passes in front of its host star, the telescope detects the corresponding dip in brightness.

If the telescope detects the same dip over a constant time period, scientists can infer that a planet or another star is orbiting the star. The Kepler Mission has a computer program that detects all these dips in starlight automatically, but it requires that an object cross in front of the star three times in order for the program to classify it as an object of interest.

The discovery of Kepler-150 f was unique because the planet crossed in front of the star only twice, and the Kepler computer program was not able to make note of it, according to the study. Given that experts have already extensively studied the data from Kepler, the discovery of a fifth planet is significant in that it had been overlooked repeatedly.

“Presumably, a bunch of people already looked at this data by eye,” Schmitt said. “And I think that the reason they didn’t see it is because there were so many other dips from the other known planets that on the two dips that were new, that were caused by this new planet, they didn’t really recognize it for what it was. They didn’t realize this was going to be a different planet, rather than one of the old planets.”

According to Yale astronomy professor Gregory Laughlin, the fact that this discovery was based on two signals from the telescope does not decrease the credibility of the planet’s existence. Laughlin explained that many dips in brightness would be required to conclude the existence of a new Earth-sized planet, but that a smaller number of clear dips would be sufficient in the case of a larger planet.

The Yale astronomers were able to find the two signals transmitted by Kepler-150 f by removing all the signals received from the known planets. This method made the two signals stand out more clearly.

The finding is significant because it demonstrates that new data is not necessarily required for new discoveries, Laughlin explained. This is particularly promising because Yale has access to data from the Palomar telescope and its infrared detector, in addition to other advanced telescopes.

“Others went through those data sets very carefully when they came out,” Laughlin said. “The fact that there are still these gold nuggets sitting there is quite remarkable. It points towards the importance of putting the analysis techniques that they used to discover this particular planet in the Kepler data to use in the new data sets that are going to be coming out from NASA’s [Tropospheric Emission Spectrometer] mission launching next year.”

Of more than 3,500 exoplanets that have been discovered, around 2,500 have been discovered as a result of the Kepler Mission, Schmitt said.