No new planets have been spotted in our solar system since Neptune was identified in 1846 (I'm excluding Pluto, discovered in 1930, because it has been since demoted to a dwarf planet). But this doesn't necessarily mean that our solar family is complete. There may be stragglers out there we haven't found yet.
Over the past year, mounting evidence suggests that a Neptune-sized world is orbiting the Sun at a distance of at least 30 billion kilometers (19 billion miles), about 200 times the orbit of the Earth around our star. The gravitational signature of this mysterious "Planet Nine," as it has been dubbed, was described in January 2016 by Caltech astronomers Konstantin Batygin and Michael Brown, but nobody has produced a firm visual yet.
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Fortunately, that may change soon, thanks to the new NASA-funded website Backyard Worlds: Planet 9, launched on Wednesday. Though the project sounds like a mashup between an Ed Wood movie and a scifi-themed porno, it is shaping up to be a thriving space for citizen scientists looking to nab the honor of the first look at this hypothesized sibling planet, which may be a foreign visitor captured by the Sun's gravity—or perhaps an exiled reject, uprooted from the inner solar system to the far edge of the Kuiper Belt. Either way, the search is on.
Here's the rundown: Backyard Worlds displays infrared images taken by the Wide-field Infrared Survey Explorer (WISE) spacecraft, which specializes in spying dim objects like distant planets or failed stars known as "brown dwarfs." Site users can examine flipbook-style image sets, tag moving objects in them for classification, and share the results with the wider community.
The hope is that this will lead to crowdsourced observations of the much-anticipated Planet Nine, as well as other dim objects inside and around the solar system. Though it is intended for the public, the project is a collaboration of researchers based at NASA, the American Museum of Natural History, Arizona State University, UC Berkeley, the Space Telescope Science Institute, and citizen science portal Zooniverse.
It's exciting to think we may be months, weeks, or even days away from pinpointing the whereabouts of the ninth planet-sized world in the solar system—if it really does exist—and that it may not be a seasoned astronomer who seizes this milestone. It could be anyone with an internet connection. Happy hunting!
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