Astronomers in the US have inferred the existence of an unknown ‘planetary mass object’ affecting the movements of space rocks in a distant asteroid belt
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It seems the Solar System may be a little more crowded than we thought: a planet around the size of Mars could be hidden among its outer fringes.
A team from the University of Arizona has discovered a mysterious mass, dubbed Planet Ten, that appears to be tugging at the orbits of a population of space rocks known as the Kuiper Belt in the icy outskirts of the Solar System.
The Kuiper Belt lies beyond the orbit of Neptune and extends to a few hundred Astronomical Units (AU) with one AU representing the distance between Earth and the Sun.
The Earth and the other major planets all orbit the Sun in roughly the same plane. However, Kuiper Belt Objects (KBOs) are far enough away from the gravitational attraction of the gas giants to be tilted away from this plane, and are affected by interactions with one another.
This angle, known as the inclination, can be calculated. If the observed angle differs from the one calculated, then it’s possible that the smaller KBOs are being pulled out of line by something more massive – potentially an undiscovered planet. This method is how the existence of the so- called Planet Nine was predicted last year.
After analysing more than 600 objects in the Kuiper Belt, the researchers found a discrepancy of 8° at around 50AU away from the Sun.
“The most likely explanation for our results is that there is some unseen mass,” said researcher Kat Volk. “According to our calculations, something as massive as Mars would be needed to cause the warp that we measured.”
The researchers say we may not have directly observed the planet because we haven’t yet searched the entire sky for distant objects in the Solar System. However, a chance may come in 2020 when the Large Synoptic Survey Telescope (LSST) is completed.
“We expect LSST to bring the number of observed KBOs from currently about 2,000 to 40,000,” researcher Renu Malhotra said. “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 MOST LIKELY EXPLANATION FOR OUR RESULTS IS THAT THERE IS SOME UNSEEN MASS”
Artist’s impression of Planet Ten
Planet Ten orbits beyond Neptune on a different plane to the other planets