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New Horizons crosses Neptune's orbit 25 years after Voyager 2

Jenny Winder, News Writer
Aug 27, 2014, 13:24 UTC

Sen—NASA's New Horizons spacecraft has traversed the orbit of Neptune on the 25th anniversary of the historic encounter of the Voyager 2 spacecraft with Neptune on 25 August, 1989.

New Horizons launched in January 2006 and reached Neptune's orbit, nearly 2.75 billion miles (4.4. billion kilometres) from Earth, in a record eight years and eight months. It will become the first probe to make a close encounter with Pluto on 14 July, 2015.  

"It's a cosmic coincidence that connects one of NASA's iconic past outer Solar System explorers, with our next outer Solar System explorer," said Jim Green, director of NASA's Planetary Science Division.

"Exactly 25 years ago at Neptune, Voyager 2 delivered our 'first' look at an unexplored planet. Now it will be New Horizons' turn to reveal the unexplored Pluto and its moons in stunning detail next summer on its way into the vast outer reaches of the Solar System."

The piano-sized spacecraft was about 2.48 billion miles (nearly 4 billion kilometres) from Neptune as it crossed the giant planet's orbit at 7:04 p.m. PDT (10:04 p.m. EDT) Monday (0304 UT, Tuesday). Although the spacecraft was much farther from the planet than Voyager 2's closest approach, New Horizons' telescopic camera was able to obtain several long-distance "approach" shots of Neptune on 10 July.


New Horizons captured this view of the giant planet Neptune and its large moon Triton on July 10, 2014 Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Several senior members of the New Horizons science team were young members of Voyager's science team in 1989. Many remember how Voyager 2's approach images of Neptune and its planet-sized moon Triton fuelled anticipation of the discoveries to come. They share a similar, growing excitement as New Horizons begins its approach to Pluto.

"The feeling 25 years ago was that this was really cool, because we're going to see Neptune and Triton up-close for the first time," said Ralph McNutt of the Johns Hopkins University Applied Physics Laboratory (APL), who leads the New Horizons energetic-particle investigation and served on the Voyager plasma-analysis team. "The same is happening for New Horizons. Even this summer, when we're still a year out and our cameras can only spot Pluto and its largest moon as dots, we know we're in for something incredible ahead."

Many researchers feel the 1989 Neptune flyby might have offered a preview of what's to come next summer. Scientists suggest that Triton, with its icy surface, bright poles, varied terrain and cryovolcanoes, is a Pluto-like object that Neptune pulled into orbit.

Scientists recently restored Voyager's footage of Triton and Dr Paul Schenk, a scientist at the Lunar and Planetary Institute used Voyager data to construct the best-ever global colour map of Triton, as Sen reported on Monday. The map has a resolution of 1,970 ft (600 metres) per pixel.


The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Image credit: NASA/JPL-Caltech/Lunar & Planetary Institute

"There is a lot of speculation over whether Pluto will look like Triton, and how well they'll match up," McNutt said. "That's the great thing about first-time encounters like this, we don't know exactly what we'll see, but we know from decades of experience in first-time exploration of new planets that we will be very surprised."

Similar to Voyager 1 and 2's historic observations, New Horizons also is on a path toward potential discoveries in the Kuiper Belt, which is a disc-shaped region of icy objects past the orbit of Neptune, and other unexplored realms of the outer Solar System and beyond.

The Connection Between the New Horizons and Voyager Missions. Credit: NASA