NASA's New Horizons unmanned space probe has reportedly discovered a mysterious and distant celestial object beyond Pluto in the Kuiper Belt.

According to Science World Report, the 145-kilometer-wide space rock is named 1994 JR1 and orbits in the Kuiper Belt, more than 5 billion kilometers from the Sun. NASA's spacecraft released an image of the distant space rock.

New Horizons first detected the mysterious celestial body at a distance of 280 million kilometers away. The spacecraft was able later on to get a closer look at the distant space object, on April 7 and April 8. New Horizons was also able to capture images from a distance of 111 million kilometers, through the Long Range Reconnaissance Imager.

It was thought before that 1994 JR1 is just a satellite of Pluto. However, based on the images captured by New Horizons, scientists from the Southwest Research Institute (SWRI) could understand that the distant celestial object orbiting beyond Pluto is more than just a satellite of the dwarf planet.

The astronomers could identify the mysterious celestial body's position and rotation period based on the photos. It is now known that the rotation period of 1994 JR1 is 5.4 hours. This is the duration of one day on the strange rock.

John Spencer, SWRI's science team member, said that with the discovery of JR1, a new phase has opened in gathering information about more ancient celestial bodies in the Kuiper Belt. With the proposed extended mission by NASA, the New Horizons spacecraft is expected to take even closer images of these celestial bodies.

According to Popular Science, the New Horizons mission team has no plans of stopping yet. They are hoping to win this summer an extended mission to explore another mysterious new world.

The New Horizons extended mission will take the spacecraft on a super close flyby of the 2014 MU69, another object in the Kuiper Belt region. This phase of the mission is scheduled to take place around Jan. 1, 2019.