New Horizons Sights Pluto

Probe spots the dwarf planet for the first time

False-color images from New Horizons, animated to show Pluto’s movement. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

New Horizons, NASA’s Pluto-bound craft, just passed an important milestone (kilometerstone?). As reported by NASA,

The New Horizons team got a faint glimpse of the mission’s distant, main target when one of the spacecraft’s telescopic cameras spotted Pluto for the first time.

The Long Range Reconnaissance Imager (LORRI) took the pictures during an optical navigation test on Sept. 21–24, and stored them on the spacecraft’s data recorder until their recent transmission back to Earth. Seen at a distance of about 4.2 billion kilometers (2.6 billion miles) from the spacecraft, Pluto is little more than a faint point of light among a dense field of stars. But the images prove that the spacecraft can find and track long-range targets, a critical capability the team will use to navigate New Horizons toward 2,500-kilometer wide Pluto and, later, one or more 50-kilometer sized Kuiper Belt objects.

(continue reading at NASA’s web site)

Photographic plates showing movement of Pluto
The arrow indicates Pluto’s movement over the six-day interval. Credit: Lowell Observatory Archives.

The orange-red animated picture demonstrates Pluto’s movement in its orbit over the three days. Interestingly, this method is analogous to the one Clyde Tombaugh used to initially discover the recently reclassified dwarf planet, scouring pairs of photographs over months in an attempt to locate a ninth planet. At New Horizons’ distance, Pluto is just a tiny point of light surrounded by myriad stars; it is recognizable only because of its movement, and that its brightness and position correspond to Pluto’s predicted orbit. In fact, from the perspective of Earth (and of New Horizons), Pluto is near the galactic plane—indeed, near the direction of the center of the galaxy by the constellation Sagittarius—so there are more stars in this region that there would be in other fields of view. Red (instead of gray) is used to show the varying levels of brightness in order to aid in recognition.

Artist’s concept of New Horizons arriving at Pluto
Artist’s concept of New Horizons arriving at Pluto. Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI).

New Horizons was launched on on 19 January 2006, with a primary aim of exploring Pluto. It will be the first (human) spacecraft to visit that world. It is currently cruising towards Jupiter to receive a gravity assist February 2007. It will finally reach Pluto in July 2015; however, it does not have enough fuel to slow down and maneuver into orbit; it will observe Pluto and Charon as well as the two smaller moons, Nix and Hydra, as it flies by. After that, it will continue exploring the Kuiper Belt, where NASA mission planners hope to identify one or more Kuiper Belt objects (Pluto is the largest KBO) for New Horizons to study as it flies by them as well.

(thanks to the Bad Astronomy Blog)

Further reading