NASA's New Horizons probe has just flown past Ultima Thule, an icy object 6.5 billion kilometres from Earth, in the most distant exploration ever of an object in space.
New Horizons, a 470-kilogram probe launched in January 2006, sent images of Ultima Thule back to Earth on New Year's Day. The images revealed the object to be a bowling pin shape approximately 32 kilometres long, spinning like a propeller in its orbit.
The signals from New Horizons were sent to the mission's operation centre at Johns Hopkins Applied Physics Laboratory (APL) 10 hours after the spacecraft made its closest approach to Ultima Thule (a distance of 3,500km).
Ultima Thule is an object in the Kuiper Belt, a region of primordial space objects that NASA states could hold the key to understanding our solar system.
The reach of the sun in the Kuiper Belt is so dim that the temperature is around -230C, meaning that chemical reactions are frozen in time and the objects in the belt are preserved in the state that they originally formed 4.6 billion years ago.
The signals from New Horizons confirm that the spacecraft is still healthy and has now filled its digital recorders with data from its mission.
The probe will continue to download images and other data over the coming months, with all data expected to be returned to Earth within 20 months using the probe's 15-watt transmitter.
New Horizons was launched with the intention of observing Pluto and its moons as well as the Kuiper Belt, to understand their composition and place within the solar system.
New Horizons was the fastest spacecraft to ever leave Earth's orbit and travels at a speed of 58,536km/h (a bullet typically travels at around 4,500 km/h).
The spacecraft performed its flyby study of Pluto in 2015 and will now continue to travel past the Kuiper Belt and possibly exit the solar system.
The only two spacecrafts that have left the Solar System before are the Voyager 1 and Voyager 2 missions, which were launched in 1977 and crossed into interstellar space in 2012 and 2018 respectively.