July 8, 2008. Copyright, 2008, Graphic News. All rights reserved

New Horizons -- beyond the edge of our solar system

LONDON, July 8, Graphic News: An unmanned NASA spacecraft which has now travelled 1.5 billion kilometres (about 935 million miles) from Earth,  has become the first craft to journey beyond SaturnÕs orbit since Voyager 2 passed the ringed planet nearly 27 years ago. 

Launched in January 2006, the piano-sized New Horizons probe is spinning in electronic hibernation on a nine-year journey to Pluto, a Òdwarf planetÓ on the edge of our solar system. 

New Horizons crossed SaturnÕs orbit in June, just two years and five months after launch, making the fastest ever transit to Saturn. This was achieved by skimming past the giant planet Jupiter and using its gravity to boost the craftÕs speed to a record-breaking 65,740km/h (40,850mph)

Because it is flying too far from the sun for solar-powered electical systems to work, New Horizons uses radioisotope thermoelectric generators. These convert heat from the decay of radioactive plutonium pellets into electricity for the spacecraftÕs systems and science instruments.

Once known as the smallest, coldest, and most distant planet from the Sun, Pluto has been enshrouded in controversy since its discovery in 1930. In 2006 the International Astronomical Union formally downgraded Pluto from a planet to a dwarf planet, and in June this year the IAU again reclassified the heavenly body as a ÒplutoidÓ.

The move has left New Horizon principal investigator Dr. Alan Stern steaming. ÒPlutoids or haemorrhoids, whatever they call it. This is irrelevantÓ, said Stern, Òif it looks like a dog and barks like a dog, itÕs a dogÉ even if itÕs a chihuahuaÓ.

New Horizons will begin long range imaging six months prior to its arrival at Pluto on July 14, 2015. After hurtling 4.9 billion km (3.1 billion miles) through space, the probe will perform a 30-minute flyby to within 9,600km (5,900 miles) of PlutoÕs surface. During the flyby the probe will map PlutoÕs surface to 1.6km (one-mile) resolution and measure its thin atmosphere. After passing Pluto, New Horizons will head out to the distant region of the solar system called the Kuiper Belt, then on to the stars.

Kuiper Belt Objects far outnumber the so-called terrestrial inner planets -- Mercury, Venus, Earth and Mars -- as well as the gas giants of the outer solar system, Jupiter, Saturn, Uranus and Neptune. KBOs are believed to contain materials largely unchanged since they were formed at the birth of the solar system, some 4.6 billion years ago.

ÒStudying Pluto, Charon and the Kuiper Belt Objects are key to understanding the origin and evolution of the solar system,Ó said Stern. The craft, which is carrying some of the ashes of Pluto discoverer Clyde Tombaugh, will travel another 290 million km (180 million miles) beyond Pluto and continue to explore primordial objects in the Kuiper Belt until its plutonium fuel source finally runs out in 2025.
/ENDS