NASA explorer believed to have reached solar system’s outermost region

A NASA explorer is believed to have reached the solar system’s outermost region early Tuesday morning, flying close to a space rock 20 miles long and billions of miles from Earth on a mission to gather clues about the creation of the solar system.

The body is farther from Earth than any other that has had such a close encounter with a NASA probe, scientists believe.

The New Horizons probe was slated to reach the “third zone” in the uncharted heart of the Kuiper Belt at 12:33 a.m. Eastern. Scientists will not have confirmation of its successful arrival until the probe communicates its whereabouts through NASA’s Deep Space Network at 10:28 a.m. Eastern, about 10 hours later.

Once it enters the peripheral layer of the belt, containing icy bodies and leftover fragments from the solar system’s creation, the probe will get its first close-up glance of Ultima Thule, a cool mass shaped like a giant peanut, using seven on-board instruments.

Scientists had not discovered Ultima Thule when the probe was launched, according to NASA, making the mission unique in that respect. In 2014, astronomers found Thule using the Hubble Space Telescope and selected it for New Horizon’s extended mission in 2015.

Ultima is in what's termed the Kuiper belt - the band of frozen material that orbits the Sun more than 2 billion km further out than the eighth of the classical planets, Neptune; and 1.5 billion km beyond even the dwarf planet Pluto, which New Horizons visited in 2015.

It's estimated there are hundreds of thousands of Kuiper members like Ultima, and their frigid state almost certainly holds clues to the formation conditions of the Solar System 4.6 billion years ago.

“Anything’s possible out there in this very unknown region,” John Spencer, deputy project scientist for New Horizons, told reporters on Monday at the Johns Hopkins Applied Physics Laboratory in Maryland.

During a 2015 fly-by, the probe found Pluto to be slightly larger than previously thought. In March, it revealed that methane-rich dunes were on the icy dwarf planet’s surface.