Planet Nine could exist at the most distant reaches of our solar system, according to observations of the orbits of far-flung objects. This theoretical world would be 10 times as massive as Earth, and take between 10 and 20,000 years to orbit the Sun. However, such a planet would be so dark and distant that some astronomers speculate it may be 1,000 years before we discover it.Read More Is Planet Nine Hiding at the Edge of the Solar System?
A wall of hydrogen gas in the distant solar system has been spotted by astronomers. The object was seen in ultraviolet light by the New Horizons spacecraft, which visited Pluto in 2015. This wall is formed when hydrogen from the sun meets gas floating between the stars, and is compacted as our family of planets travels through the galaxy.Read More New Horizons Views Hydrogen Wall Near Edge of Solar System