Ten years after: Kepler’s first planet confirmed
Months after NASA’s orbiting telescope shut down, its work is verified. Andrew Masterson reports.
A decade after it was first detected, astronomers have confirmed the existence of the first exoplanet ever spotted by NASA’s Kepler mission.
The confirmation comes just four months after the Kepler space telescope itself – originally launched in March 2007 – ceased operation, having burned its entire fuel load.
When its journey began, the telescope’s mission was to survey a portion of the Milky Way in order to spot roughly Earth-size exoplanets. It did this by using a photometer to monitor the brightness of around 150,000 nearby stars.
An exoplanet passing in orbit in front of any of the target stars would cause a temporary dip in luminosity, and it was this type of phenomenon that the telescope was designed to detect.
However, astronomers are necessarily a cautious bunch. A Kepler result is regarded as a promise, not a done deal, because other phenomena can also cause temporary brightness-dipping. Thus, every potential exoplanet discovered by the telescope – and there are thousands of them – has to be painstakingly confirmed by other methods.
Thus, 10 years later, the confirmation of the first find has been completed and the existence of the unromantically named exoplanet Kepler-1658 b, which orbits a star with equally unromantic name, Kepler-1658, is now beyond dispute.
The confirmation was made by a team of astronomers led by Ashley Chontos from the University of Hawaii.
It was not, however, an open-and-shut case. An earlier attempt at verification had found large discrepancies in the data and Kepler-1658 b had been dismissed as a false positive result.
Chontos and his team decided to come at the figures from a different perspective.
“Our new analysis, which uses stellar sound waves observed in the Kepler data to characterise the host star, demonstrated that the star is in fact three times larger than previously thought,” he says.
“This in turn means that the planet is three times larger, revealing that Kepler-1658 b is actually a hot Jupiter-like planet.”
It is also uncomfortably close to its host, orbiting at a distance of just twice the diameter of the star. Such occurrences are rare, and astronomers are unsure why. The Kepler-1658 b confirmation will help to eventually answer the question.
The work of Chontos and his colleagues will soon be published in the Astronomical Journal. A preprint is available here.