NASA’s unmanned New Horizons spacecraft has reportedly discovered a mysterious and distant celestial object beyond Pluto named 1994 JR1 which orbits in the Kuiper Belt, more than 5 billion kilometers from the Sun. NASA has released an image of space rock captured by New Horizons in the distance.

The mysterious second target is a planet codenamed 1994 JR1, which was originally spotted in April 2015 and fully detected in November. This distant celestial object has been first detected by the spacecraft at a distance of 280 million kilometers away. Later on NASA’s New Horizons was able to get a closer look at the space object, on April 7 and 8. The probe has also captured the images from a distance of 111 million kilometers, through the Long Range Reconnaissance Imager.

According to New Horizons team member John Spencer of Southwest Research Institute, the object measures 90 miles wide and rotates once every 5.4 hours, making it unusually fast for a small Kuiper Belt Object. It orbits about 3 billion miles away from our Sun.

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.