Gaia. Rooting out
planetary impostures.
K’s false positives.
The Kepler Space Telescope was designed to discover earth-sized planets orbiting around other stars within our region of the Milky Way. Named after German astronomer and mathematician, Johannes Kepler, it was launched in 2009 and retired on the 15th November 2018, the 388th anniversary of the death of its namesake in 1630.
During its lifetime the Kepler Space Telescope discovered 2,662 planets, something it achieved by observing 530,506 stars and looking for drops in their intensity that could indicate a planet passing in front of them. Among these planets were some that were the correct distance from their star and had the right size and atmospheric pressure to support liquid water at the planet’s surface. Other planets discovered orbited two stars instead of one, and ‘hot Jupiters’ – gas giants similar to Jupiter but orbiting in close proximity to their star.
Yet telescopes continue to advance technologically. The Kepler Space Telescope used a photometer to observe the stars in its field of view. The Gaia Space Observatory, launched in 2013, uses a photometer along with an astrometry instrument and a radial-vector spectrometer.
Now research by Niraula et al. (2022) suggests that three or even four of the planets identified by the Kepler Space Telescope aren’t planets at all but are in fact stars. The team was reviewing the planetary data produced by the Kepler Space Telescope and realised that with updated measurements from the Gaia Space Observatory the ‘planets’ Kepler-854b, Kepler-840b, and Kepler-699b were far too large to be planets – each of them two to four times the size of Jupiter. The fourth ‘planet’, Kepler-747b, is 1.8 times the size of Jupiter, at the very top end of observed planets, but its far distance from its star suggests that its more likely to be a star itself than a planet.
Four out of over two and a half thousand discovered planets isn’t a large amount and certainly doesn’t take anything away from the incredible job that the Kepler Space Telescope did during its lifetime. Yet the new findings are hugely important for our knowledge and understanding of planets – by correcting this error the planet dataset is more accurate for those who are studying the population of planets as a whole.
Original research: http://dx.doi.org/10.3847/1538-3881/ac4f64