Physics theory suggests that the universe is made up in great part by a type of matter that does not emit, absorb or reflect light, and hence cannot be observed using conventional detection methods. This type of matter, referred to as dark matter, has so far never been experimentally observed or detected.

Ninety years ago today, Clyde Tombaugh, a young astronomer working at Lowell Observatory in Flagstaff, Arizona, discovered Pluto. In doing so he unknowingly opened the door to the vast "third zone" of the solar system we now know as the Kuiper Belt, containing countless planetesimals and dwarf planets—the third class of planets in our solar system.

A fireball in the sky, accompanied by a bang, amazed hundreds of eyewitnesses in northern Germany in mid-September last year. The reason for the spectacle was a meteoroid entering the Earth's atmosphere and partially burning up. One day after the observations, a citizen in Flensburg found a stone weighing 24.5 grams and having a fresh black fusion crust on the lawn of his garden.

NASA's space snowman is revealing fresh secrets from its home far beyond Pluto.

Last month, SpaceX became the operator of the world's largest active satellite constellation. As of the end of January, the company had 242 satellites orbiting the planet with plans to launch 42,000 over the next decade. This is part of its ambitious project to provide internet access across the globe. The race to put satellites in space is on, with Amazon, U.K.-based OneWeb and other companies chomping at the bit to place thousands of satellites in orbit in the coming months.