Kepler-1658 b, the First exoplanet spotted by Kepler finally confirmed

James Marshall
March 8, 2019

In 2009, NASA's groundbreaking Kepler mission identified its first potential exoplanet.

Specifically, Kepler saw a pronounced "secondary eclipse" in the system - a significant drop in total light caused when the candidate went behind the host star from the telescope's perspective.

"Confirming that Kepler's first exoplanet candidate really is a planet is a wonderful legacy result, which brings things full-circle, now that Kepler has finished taking data", Bill Chaplin, an author of the study from the University of Birmingham in the United Kingdom, said in a statement. This meant that the sizes of both the star and the planet were significantly underestimated and thus scientists were unable to explain certain characteristics of the proposed system. It was later marked as a false positive - that is, scientists thought the data did not really point to a planet - when the numbers didn't quite add up for the effects seen on its star for a body of that size.

But because other cosmic phenomena can mimic transits-small dips in a star's brightness as planets cross in front of it-further analysis is required to confirm each candidate as genuine planets.

"Our new analysis, which uses stellar sound waves observed in the Kepler data to characterize Kepler-1658, demonstrated that the star is in fact three times larger than previously thought", said University of Hawai'i graduate student Ashley Chontos.

Reference: "The Curious Case of KOI 4: Confirming Kepler's First Exoplanet Detection", A. Chontos et al., 2019, to appear in the Astronomical Journal [, preprint (PDF):]. Despite being the first-ever planet candidate presented by the telescope in 2011, Kepler-1658 b took a lot of time to be confirmed.

"We alerted Dave Latham (a senior astronomer at the Smithsonian Astrophysical Observatory, and co-author on the paper) and his team collected the necessary spectroscopic data to unambiguously show that Kepler-1658 b is a planet", said Dan Huber, co-author and astronomer at the University of Hawaii.

Now it's clear why: These planets are permanently off-kilter - tipped over on their sides, new research suggests. New software was developed and used to refine the data and reclassify it, Kepler-1658b was again a possible planet. Past studies proposed that planetary tides could play a part by absorbing orbital energy as heat; this could tug the planets into orbits that slightly exceeded the usual ratios, according to the study.

Kepler-1658 b is ideal for follow-up observations by other space telescopes in the future to learn how hot Jupiters evolve and form. It whips around its star every 3.85 days. Kepler-1658 is a ideal example of why a better understanding of host stars of exoplanets is so important. A Neptune-size world orbiting a sunlike star would not produce an observable secondary eclipse, astronomers said.

But numerous paired exoplanets found by Kepler defied those rules.

TESS, the Transiting Exoplanet Survey Satellite, launched in April 2018 and is the newest planet hunter for NASA.

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