When Pluto lost its planetary status in 2006 it left a dark hole in our hearts. Luckily, the existence of another planet in our solar system was predicted in 1846, and recently it has started to seem like there might be enough evidence to support that prediction. A few months on, astronomers think they may have worked out a way to find it.
Mathematical modelling and computer simulations done by Konstantin Batygin and Mike Brown at Caltech show that if a ninth planet does exist, it will explain the strange behaviour of six dwarf planets in the Kuiper belt, beyond Neptune. These dwarfs ‘clump together’, and have elliptical orbits tilted out of the plane of the rest of the solar system, which has a probability of occurring of just 0.007% without a larger object influencing them.
Planet modelling specialists Christoph Mordasini and Ester Linder from the University of Bern have done analysis to determine the properties of the suggested object. They modelled various combinations of masses and distances from the Sun leading to one plausible model – a planet the size of Neptune, 700 times further from the Sun than the Earth, and only -226 degrees Celsius on the surface. They predict that it has an outer atmosphere of helium and hydrogen, a water ice layer, a silicate mantle and an iron core, similar to that of Neptune and Uranus.
With the planet predicted to be so far away, it will be difficult to detect based solely on the reflection of the Sun’s light. Instead, studies from McGill University in Canada and the Hebrew University of Jerusalem have suggested that astronomers may be able to detect infrared and microwaves emitted from the planet as its core cools. Conveniently, current telescopes, like Subaru in Hawaii, are advanced enough to detect these waves and resolve them from waves from other sources.
Some astronomers say that there are too many problems with the suggested planet. It seems unlikely that the planet could have been created so far from the Sun, where there isn’t enough dust and gas to form a planet, and that it could be stable in the elliptical orbit and not collide with other objects. Batygin and Brown suggest that the planet formed closer to the Sun, and then moved out due to interactions with other planets. And it apparently wouldn’t collide with the other objects due to the motion resonating with the motion of other objects in the Kuiper belt, preventing any possible collisions by exchanging energy. This creates periodic nudges which mean that the objects remain in the same positions relative to each other.
If planet nine does exist, it would not only explain a lot of weird phenomena, but would make solar system more similar to known systems. And it would replace the much-missed Pluto!
M. E. Brown, K. Batygin, Observational Constraints on the Orbit and Location of Planet Nine in the Outer Solar System, http://arxiv.org/pdf/1603.05712v1.pdf (accessed 01/05/2016)
N. B .Cowan, G. Holder, N. A. Kaib, The Astrophysical Journal Letters, 22nd April 2016, Cosmologists in Search of Planet Nine: the case for CMB experiments, http://iopscience.iop.org/article/10.3847/2041-8205/822/1/L2 (accessed 01/05/2016)
S. Ginzburg, R. Sari, A. Loeb, The Astrophysical Journal Letters, 27th April 2016, Blackbosy Radiation from Isolated Neptunes, http://iopscience.iop.org/article/10.3847/2041-8205/822/1/L11 (accessed 01/05/2016)
Brendan Cole, Science Alert, 29th April 2016, Physicists think they’re finally figured out how to locate planet nine, http://www.sciencealert.com/physicists-have-come-up-with-new-ways-to-find-mysterious-planet-nine (accessed 01/05/2016)
Maddie Stone, Gizmodo, 8th April 2016, How Astronomers are Going to Find Planet Nine, http://www.gizmodo.co.uk/2016/04/how-astronomers-are-going-to-find-planet-nine/ (accessed 01/05/2016)
George Dvorsky, Gizmodo, 10th April 2016, The Best Guess at What ‘Planet Nine’ Looks Like, http://www.gizmodo.co.uk/2016/04/the-best-guess-at-what-planet-nine-looks-like/ (accessed 01/05/2016)