NASA scientists are calling on space fans to track down Planet Nine, a yet undiscovered world that is thought to exist deep in our Solar System. They want help checking out nearly 750 million photos of the sky taken by a space telescope orbiting the Earth.
The existence of so-called Planet Nine was proposed in January last year. Astronomers reckon it is around ten times the size of Earth, and say it gave itself away by its gravitational pull on other distant objects.
The space telescope is called WISE – short for Wide-field Infrared Survey Explorer. It was launched in late 2009 and has mapped the entire sky several times over seven years.
There are far too many images from WISE for astronomers to search on their own. But they are being displayed on a new NASA-funded website, called Backyard Worlds, where the public can help with the detective work.
By observing in infrared light, WISE is able to detect objects that would otherwise be too faint to see. The website allows citizen scientists to compare the same patches of sky, like pictures in a flipbook, revealing anything that moved over that time.
The idea is that, even in a slow orbit taking thousands of years to orbit the Sun, Planet Nine would show itself by shifting from one position to another.
Planet Nine is thought to travel in an orbit at a steep angle to that of the other planets, and at an average distance of 55 billion miles, or around 20 times the distance of present outer planet Neptune. It probably takes between 10,000 and 20,000 years to make one orbit of the Sun.
The evidence for hypothetical Planet Nine came from effects on the orbits of asteroid-like icy bodies in an outer zone of the Solar System called the Kuiper Belt.
The new search for Planet Nine is being led by Dr Adam Schneider and colleagues from Arizona State University. He said: “If it exists, Planet 9 could be large — maybe 10 times the mass of Earth but orbiting far out beyond the Kuiper Belt. Yet it must be extremely dim and hard to find.”
The astronomers hope that the new search will reveal not just Planet Nine but also dim objects called brown dwarfs in the Sun’s neighbourhood. Sometime called “failed stars”, they are believed to be numerous in the Galaxy and some could lie closer than the nearest known stars.
Dr Schneider said: “Brown dwarfs are somewhat mysterious. They have masses of less than 80 times that of Jupiter, because that’s the point at which nuclear fusion begins and an object becomes by definition a star.”
Marc Kuchner, an astrophysicist at NASA’s Goddard Space Flight Center, commented: “There are just over four light-years between Neptune and Proxima Centauri, the nearest star, and much of this vast territory is unexplored.”
The Backyard Worlds website, which is part of the Zooniverse family of citizen science activities, can be found here. WISE has begun a new project to locate asteroids that might be an impact threat to Earth.