Evidence of giant Planet Nine discovered in outer solar system

20 Jan 2016

Astronomers are getting rather excited about the news that a giant planet 10-times the mass of Earth and dubbed ‘Planet Nine’, has likely been discovered on the fringes of our solar system.

For a number of decades, astronomy had considered our solar system’s ninth planet to be little Pluto, which, to the annoyance of many, was downgraded to a dwarf planet in 2005, leaving us with eight identified planets in our region.

But now, according to researchers at the California Institute of Technology (Caltech), there is considerable evidence for the existence of a giant planet past Pluto, which is being simply referred to as Planet Nine.

In terms of scale, the research team of Konstantin Batygin and Mike Brown (who stripped Pluto of its planet status), say the planet is enormous with not only a mass 10-times as large as ours but an orbit that is 20 times farther from the sun than Neptune.

Planet Nine takes between 10,000 years and 20,000 years to make a complete orbit of the sun and, unlike its nearest neighbour Pluto, which has 5,000-times less mass is, without doubt, a planet.

Publishing their findings in the Astronomical Journal, the researchers say they had actually doubted the existence of Planet Nine before embarking on the research, but the subsequent evidence made its future adoption into our solar system charts more and more likely.

The origin of the study has been 13 years in the making following Brown’s discovery of the unusual orbits of two objects in the outer reaches of the solar system, known as the Edgeworth-Kuiper belt.

One of these objects, dubbed Sedna, was found to be different from other objects in the region by showing it was not affected by Neptune’s gravitational pull.

In the years that followed, five objects with identical orbits to Sedna were also discovered, which was considered so astronomically unlikely that something else must have been contributing to the bizarre orbit.

It couldn’t be a planet, surely?

A number of explanations were suggested by astronomers and the two researchers, including the possibility that the sheer number of Edgeworth-Kuiper Belt objects could create the necessary gravitational pull on Sedna, although this was quickly ruled out.

It was only after it was suggested that it could be a planet, and the necessary simulations were run, was it determined that a planet was the answer they were looking for.

Although we were initially quite sceptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we become increasingly convinced that it is out there,” Batygin said of the discovery. “For the first time in over 150 years, there is solid evidence that the solar system’s planetary census is incomplete.”

Planet Nine orbit

The estimated orbit of the so-called Planet Nine. Image via Caltech/ R Hurt (IPAC)

However, while astronomical analysis and simulations would show evidence for the existence of a large gaseous planet, the researchers are still looking to answer how Planet Nine found itself in such a remote location, especially given its size, which would make it a difficult place to birth such a planet.

There is also the little issue of actually finding its actual location and, for everyone here on Earth, capturing sight of the planet to move it from a very credible theory to 100pc confirmation.

I would love to find it,” Brown said. “But I’d also be perfectly happy if someone else found it. That is why we’re publishing this paper. We hope that other people are going to get inspired and start searching.”

And, Brown says, there’s a caveat for all those who continually call for the re-introduction of Pluto as our solar system’s ninth planet: “All those people who are mad that Pluto is no longer a planet can be thrilled to know that there is a real planet out there still to be found. Now we can go and find this planet and make the solar system have nine planets once again.”

Giant gaseous planet image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic