New Horizons launch — to Pluto

The fastest launch in history — nine and a half years later it would reveal Pluto's heart.

The moment of New Horizons launch — to Pluto: https://nowsky.org/e/newhorizons-launch — opens at the right place and time, replayable, no login.

Available views: Orbit ✓ · Sky — (not visible in the sky)

The story

On 19 January 2006 New Horizons left Earth on an Atlas V at 58,000 km/h — the fastest launch speed ever recorded — and crossed the Moon's orbit in nine hours, a trip that took Apollo three days. The design traded mass for speed: the whole spacecraft weighed about as much as a grand piano (478 kg).

At departure its target Pluto was still the ninth planet; that August the International Astronomical Union reclassified it as a dwarf planet. Aboard is a portion of the ashes of Clyde Tombaugh, Pluto's discoverer — the discoverer became the first visitor to the world he found.

The hurry was about Pluto's atmosphere. Having passed perihelion in 1989, Pluto was receding from the Sun, and the probe had to arrive before the nitrogen atmosphere froze out onto the surface. A Jupiter gravity assist in February 2007 added 4 km/s and cut three years off the trip; most of the next eight years were spent in hibernation.

It passed Pluto at 12,500 km on 14 July 2015 and went on to fly past the Kuiper-belt object Arrokoth in 2019. Now beyond 60 AU it continues to observe the outer heliosphere. The orbit replay shows the nine-and-a-half-year straight run.

Why it matters

New Horizons was the first exploration of the solar system's "last planet" and revived, after thirty years, the era of first flybys. As Mariner, Pioneer and Voyager each showed a planet for the first time, New Horizons showed Pluto for the first time and made the first close observations of a Kuiper-belt object.

The probe physically carried on the 2006 debate that turned Pluto from planet to dwarf planet. The 2015 images — nitrogen glaciers, 3,500 m ice mountains, layered blue haze — showed that whatever the label, Pluto is a geologically living world.

The combination of record launch speed and a Jupiter assist became the template for direct outer-planet missions; later designs such as Juno (2011) repeat the "maximum launch speed plus one gravity assist" pattern.

How to watch

New Horizons lies toward Sagittarius at about 62 AU and is beyond any telescope. Follow the probe in the orbit view for its current position, the straight track since leaving Earth and the point of the Jupiter flyby.

The orbit replay runs from the January 2006 launch through the 2007 Jupiter pass to arrival at Pluto in 2015; at high speed the slight bend and gain in speed at Jupiter can be seen.

Pluto itself is 14th magnitude and needs a 30 cm amateur telescope to show as a point. Select Pluto in the sky view for its current place in Sagittarius; in the 3-D interstellar view New Horizons is marked at the edge of the solar system beside Voyager 1, Voyager 2 and Pioneer 10.

See this for yourself — replay the moment in the orbit view

Background

A Pluto mission was cancelled twice in the 1990s (Pluto Fast Flyby, Pluto–Kuiper Express). It was revived in 2000 by public petition and a National Academies priority ranking; New Horizons was selected in 2001 and launched five years later.

The launch window was narrow — January to early February 2006 — because of the Jupiter assist. Past early February Jupiter would have moved out of position and a direct trip would have taken twelve years. After two delays for high winds and a power outage on 17 and 18 January, it left on the 19th.

After Pluto it passed Arrokoth (2014 MU69) at 3,500 km on 1 January 2019 — a snowman-shaped contact binary and the most distant object ever observed up close. Power is expected to last into the late 2030s.

New Horizons runs on a single plutonium generator whose output fell from 245 W at launch to 200 W at Pluto. At 30 AU sunlight is a thousandth of Earth’s, so solar panels were never an option. A plutonium shortage at the time meant the generator was fuelled below its design load, so not all instruments could run at once and the flyby sequence was built around power budgeting. Output has fallen further since, and instruments are now cycled in turn.

FAQ

How fast was it?

58,000 km/h straight after launch — the fastest ever — crossing the Moon's orbit in nine hours.

Why go via Jupiter?

The Jupiter gravity assist added 4 km/s and cut three years off the trip to Pluto.

Is it connected to Pluto losing planet status?

Pluto was reclassified as a dwarf planet in August 2006, seven months after launch; the mission went ahead unchanged.

Where is it now?

About 62 AU out, toward Sagittarius, observing the outer heliosphere.

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Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.