New Horizons takes a portrait of Pluto

Pluto from New Horizons

One of the final images taken before New Horizons made its closest approach to Pluto on 14 July 2015. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

For nearly 10 years, the New Horizons spacecraft has been charging through space – the fastest spacecraft ever launched – on track to reach the icy outer edge of our solar system. The Kuiper Belt, as this area is known, is full of objects from icy boulder-sized rocks to dwarf planets like Pluto. Today, New Horizons made its closest approach to this once-planet – 7,750 miles from its surface, or about the distance from New York to Mumbai – and sent home the best images ever taken of Pluto.

At the same time, New Horizons’ three-billion-mile adventure marks the farthest planetary object a space mission has ever explored. The spacecraft is expected to “call home” to Earth (specifically, to Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland) at 9 p.m. ET tonight, sending updates to indicate whether it has survived its journey and will continue into the depths of the Kuiper Belt.

The trip is expected to help tell more of our solar system’s origin story.

Pluto was discovered on 18 February 1930, by the son of a Kansas farmer, at Lowell Observatory in Flagstaff, Arizona.  Percival Lowell himself had embarked on the search for Planet X – a planet beyond Neptune – in 1905 but died before Pluto was found. Since then, Pluto has been demoted from full-fledged planet to a dwarf planet, because astronomers say it is too small to clear its orbit. The distinction has not been met without controversy. Still, it has not changed our fervor for the plutoid (a dwarf planet more distant than Neptune).

New Horizons was launched before Pluto’s identity change but that did not change its course, nor diminish the significance of reaching Earth’s most distant planetary cousin. The spacecraft reached Pluto about a minute earlier than scientists planned at its launch in January 2006, and, on target. According to NASA, the 36-by-57 mile (60-by-90 km) window through which it passed in space is akin to a commercial jet arriving at its target within the width of a tennis ball.

When New Horizons calls its scientists tonight, it will commence sending 10-years’ worth of data back to Earth over the course of the next 16 months.

Jim Lattis, a regular contributor to this blog and a faculty member within the Department of Astronomy, will discuss New Horizons and the Pluto flyby on Madison’s WISC-TV Live at 5 show tonight. Lattis will also give a free talk at UW Space Place, where he serves as director, from 7 -to-8 pm tonight. Additionally, Sanjay Limaye, a scientist at the UW-Madison Space Science and Engineering Center is an expert on solar system exploration and can discuss the flyby and mission with interested media.


UW Space Place is located at 2300 S Park Street in the Villager Mall, just north of the Beltline Highway on Madison’s south side.