Saturn spacecraft immune to mysterious Planet 9's charms

Cassini orbit normal, NASA insists

NASA has been obliged to clarify that if the hypothetical Planet 9 exists, it is not responsible for "unexplained deviations" in the orbit of the Cassini spacecraft around Saturn.

Back in January, CalTech boffins Konstantin Batygin and Mike Brown claimed to have found evidence for a mysterious body, around 10 times the mass of Earth, "travelling 200 times further from the Sun than our orbit", as we put it at the time. The proof of its existence was its effect on Kuiper Belt objects, the scientists claimed.

That may well be, but Cassini is unaffected by Planet 9's gravitational charms, despite recent reports.

NASA stated last week that "mission navigators have observed no unexplained deviations in the spacecraft's orbit since its arrival there in 2004".

Planetary scientist William Folkner, of the Jet Propulsion Laboratory, elaborated: "An undiscovered planet outside the orbit of Neptune, 10 times the mass of Earth, would affect the orbit of Saturn, not Cassini.

"This could produce a signature in the measurements of Cassini while in orbit about Saturn if the planet was close enough to the sun. But we do not see any unexplained signature above the level of the measurement noise in Cassini data taken from 2004 to 2016."

While Cassini project manager Earl Maize said his team would "love it" were the spacecraft able to lend a hand in nailing Planet 9, it's going to be down to Kuiper Belt object observations to settle the matter once and for all.

In March, the trail grew warmer when SETI Institute astronomer Michelle Bannister said she'd identified an "as-yet-uncatalogued Kuiper Belt object with an alignment Batygin and Brown say fits with their predictions". ®

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