Space

Move over, Planet 9: Does a Mars-sized 10th planet lurk beyond Pluto?

Move over, Planet 9: Does a Ma...
A Mars-sized planetary body could be hiding in our Solar System beyond Pluto
A Mars-sized planetary body could be hiding in our Solar System beyond Pluto
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A Mars-sized planetary body could be hiding in our Solar System beyond Pluto
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A Mars-sized planetary body could be hiding in our Solar System beyond Pluto
The suggestion of a currently-unknown planetary body was made by studying the odd orbital planes of objects in the Kuiper Belt
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The suggestion of a currently-unknown planetary body was made by studying the odd orbital planes of objects in the Kuiper Belt
A Mars-sized planetary body could be hiding in our Solar System beyond Pluto
3/4
A Mars-sized planetary body could be hiding in our Solar System beyond Pluto
The suggestion of a currently-unknown planetary body was made by studying the odd orbital planes of objects in the Kuiper Belt
4/4
The suggestion of a currently-unknown planetary body was made by studying the odd orbital planes of objects in the Kuiper Belt
View gallery - 4 images

In January last year, astronomers from Caltech suggested that a gigantic so-far-undiscovered planet might be lurking on the fringes of the Solar System. Now researchers from the University of Arizona (UA) have found that if it exists, this so-called Planet Nine might not be alone out there. Weirdly wobbling objects in the Kuiper Belt seem to indicate the influence of yet another planetary body at least as large as Mars.

The Caltech team first hypothesized the existence of Planet Nine based on the odd orbital plane of six Kuiper Belt Objects (KBOs). These were all tilted on an angle about 30 degrees off the average, suggesting that a huge planet about 10 times larger than Earth was tugging on them from way out in the shadows. Since then, evidence for the existence of this planet has mounted, including its influence on other trans-Neptunian objects and even the Sun.

Using a similar method, the UA researchers observed the tilt angles of some 600 KBOs, and found that the most distant objects have an average orbital plane that's off-kilter by about eight degrees. That suggests the presence of another currently-undiscovered planetary body about the size of Mars, orbiting 60 times further from the Sun than Earth.

"The most likely explanation for our results is that there is some unseen mass," says Kat Volk, lead author of the study. "According to our calculations, something as massive as Mars would be needed to cause the warp that we measured."

The suggestion of a currently-unknown planetary body was made by studying the odd orbital planes of objects in the Kuiper Belt
The suggestion of a currently-unknown planetary body was made by studying the odd orbital planes of objects in the Kuiper Belt

The team gives the findings a less than two percent chance of being a statistical anomaly, and the effect is also not likely to be caused by the predicted Planet Nine. That distant giant is believed to orbit between 500 and 700 Astronomical Units (AU), but to have the observed impact it would need to be closer than 100 AU. A rogue star swinging past could have created the wobble as well, but the researchers don't consider that likely because the time scales don't quite line up.

Without having observed the mysterious object directly, the team is careful to call it a "planetary mass object" for now. The official definition of a planet, as voted by the International Astronomical Union in 2006, is "a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit."

It was that last part that got poor Pluto kicked out of the club, so until the hypothesized object has been found, it's best not to attach the label of "planet" just yet. The researchers believe that the mystery may be solved when the Large Synoptic Survey Telescope (LSST) comes online in 2020.

"We expect LSST to bring the number of observed KBOs from currently about 2,000 to 40,000," says Renu Malhotra, co-author of the study. "There are a lot more KBOs out there – we just have not seen them yet. Some of them are too far and dim even for LSST to spot, but because the telescope will cover the sky much more comprehensively than current surveys, it should be able to detect this object, if it's out there."

The research was published in the Astronomical Journal.

Source: University of Arizona

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6 comments
LaurelKornfeld
The IAU planet definition is no more "official" than is the alternative definition in this ongoing debate, which is the geophysical definition. According to the geophysical planet definition, a planet is any non-self-luminous spheroidal body orbiting a star, free floating in space, or even orbiting another planet. If an object is not a star itself and is large enough and massive enough to be squeezed into a round or nearly round shape by its own gravity, it is a planet. There is no "requirement" that an object "clear its orbit" to be a planet in this definition. The media in general and science writers in particular need to stop treating the IAU position as gospel truth, as it was adopted by just four percent of the group's members, most of whom are not planetary scientists, and was opposed by an equal number of professional planetary scientists in a formal petition.
Pluto never stopped being a planet because science is not determined by decree of "authority." In fact, New Horizons showed Pluto to have the same planetary processes as the larger terrestrial planets. The scientist who coined the term "dwarf plant," Alan Stern, intended for it to designate a third class of planets, not to designate non-planets.
The name "Planet 9" was never appropriate for the hypothesized super Earth in the outer solar system. It was chosen by someone deliberately to promote the IAU view as the only one and deny that the debate over what a planet is continues. Dwarf planets are planets too, at least according to the geophysical definition, meaning our solar system already has a minimum of 13 planets and counting.
GaryOwens
This can't be right, objects in the Kuiper Belt are are very poorly lit by our sun and are mostly small, even so these experts have managed to to detect that some of them have moved about 30 degrees out of line. Why then, I ask myself, can't they see an object many times bigger than Mars nearby causing this misaligniment ? This object must be so large compared to the smaller things nearby that they say have been moved by it, that it should almost fill the lens of their viewing device. There must be another explanation.
Bob
Funny how we have all this unseen mass so near to us. I'm surprised they haven't tried to label it dark matter.
over_there
We neel like buttons on comments so i can like Laurel and bobs very logical comments
William Juno Roehling
Just remember that the original design of this Solar System was 13-Planets, that includes our Sun, which is an actual Planet, but one of a much higher Vibrational Frequency of Light and Dimensional Densities...there are much higher Vibrational Lifeforms...Beings...that live within and below the Lower Vibrational Light Energies that are artificially created above and around our 13th Planet, we call the Sun~*
Brian M
@William Juno
'that includes our Sun, which is an actual Planet'
Don't think you can call the sun a planet, it fails both IAU and the more logical geophysical planet definition of a planet in that its 'not a non-self-luminous spheroidal body orbiting a star'
Well at least to my mind!