There is still much to be discovered in our own solar system. One of the mysteries of our solar system has been the existence of Planet X (10).
Image Source
Kuiper Belt
In a region of space in beyond the orbit of Neptune is the Kuiper Belt. The Kuiper Belt is filled with countless number of icy asteroids, comets, and dwarf planets.
Image Source
The Kuiper Belt contains the remnants of the early solar system. The Kuiper Belt is an elliptical plane within the Oort Cloud that spans a distance of 30 to 50 astronomical units (AU) from our sun.
Planet Nine (9)
Image Source
The mysterious Planet Nine was found by Caltech researchers in January 2016. It is hypothesized to be about the size of Neptune but with a highly elongated orbit on an order of 20 times further out than Neptune. Planet Nine is estimated to orbit the sun once every 10,000 to 20,000 Earth years.
Planet X (10)
By observing the average tilt of Kuiper Belts objects (KBO's) scientists at the University of Arizona's Lunar and Planetary Laboratory suspect the existence a planetary-mass object. Planet Nine is too far away from the KBO's to affect the observed tilt. The planetary-mass of the object is estimated to lie somewhere between the mass of Mars and Earth. The scientists have dubbed this new planetary-mass object as Planet X (10).
Large Synoptic Survey Telescope (LSST)
The LSST is 8.4 meter ground-based telescope currently under construction in Chile. Scientists are optimistic that this new telescope will shed light on these hidden worlds in the Kuiper Belt.
2010 Rendering of the LSST Image Source
A public private partnership of thirty-four universities and national labs have joined together to build the new telescope. This new telescope may allow scientists to see planetary-mass objects lurking in the Kuiper Belt.
Sources and Full Articles
Planet 10? Another Earth-size world may lurk in the outer solar system, SPACE.com, 23 June 2017
Kuiper Belt Objects: Facts about the Kuiper Belt & KBOs, SPACE.com, 22 January 2016
Large Synoptic Survey Telescope deemed top priority ground-based astronomical facility, Lawrence Livermore National Laboratory, 17 August 2010