Cassini orbit not influenced by phantom planet

NASA's Cassini spacecraft has been characterizing the Saturnian system since its arrival in 2004(Credit: NASA/JPL-Caltech)

NASA has released a statement casting doubt on a theory put forward by French astronomers that analyzed anomalies in the trajectory of the Cassini spacecraft in order to determine the general location of the unconfirmed solar system body "Planet Nine."

The existence of an as of yet unobserved ninth planet in our solar system has been a topic of hot debate among astronomers for some time. Konstantin Batygin and Mike Brown of Caltech recently stoked the fire by proposing that the unusual orbits of several Kuiper belt objects could have been induced by the gravitational influence of a huge planet orbiting beyond Neptune.

Based on a series of numerical simulations, the duo argued that to account for the excited orbits of the Kuiper belt objects, the offending planet would need to have a mass around 10 times that of our home world. The team also suggested that Planet Nine would follow a highly eccentric inclined orbit, which would take the mysterious body 60 billion miles (97 billion km) away from our Sun, with an anticipated orbital period of between 10,000 – 20,000 years.

Though recent observations have provided compelling evidence for a ninth planet, confirmation of such a body could only be achieved via a direct telescopic sighting. The problem is, while Batygin and Brown have provided useful theories regarding the characteristics of the phantom planet's orbit, we still have no idea where to start looking.

A team of French astronomers had hoped to narrow down the position of Planet Nine by observing the trajectory of NASA's Cassini spacecraft. In a paper published in journal Astronomy & Astrophysics, the group argued that the presence of Planet Nine would create perturbations in the movement of Saturn around the Sun.

By observing radio tracking data transmitted by the Cassini spacecraft, the astronomers had hoped to identify the signature of Planet Nine's gravitational pull, and thus infer its general position in space.

Unfortunately, a recent NASA statement has effectively debunked the theory by stating that the spacecraft had experienced no unexplained course deviations since making orbit around Saturn in 2004.

"An undiscovered planet outside the orbit of Neptune, 10 times the mass of Earth, would affect the orbit of Saturn, not Cassini," states William Folkner, a planetary scientist NASA's Jet Propulsion Laboratory. "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."

Were it possible for Cassini to continue its observational campaign of the Saturnian system up to the year 2020, then the spacecraft may have been able to collect enough tracking data to establish a probable location for the planet.

However, Cassini's dwindling fuel supply places any such ambition far out of reach, as the probe is currently scheduled to end its mission by plunging into the surface of Saturn in late 2017. With Cassini out of the picture, the location of the theoretical planet will have to be pinpointed by another, possibly as of yet unconceived, mission.

Source: NASA

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