With NASA'S New Horizons spacecraft scheduled to pass Pluto next year, the space agency has announced the discovery of three Kuiper Belt objects (KBO); one of which may be the unmanned probe’s next destination. Located in the constellation of Sagittarius, the primordial asteroids were found after a detailed survey using the Hubble Space Telescope.
The Kuiper Belt is a gigantic area on the rim of the Solar System filled with asteroids and other objects that have been preserved largely unchanged since the time when the system was formed – making them cosmic fossils of tremendous interest to astronomers.
Based on a proof of concept search conducted in June, the New Horizons team was allocated time on the Hubble from July through September. The space telescope has been looking at objects that are ten times the size of the average comet, but only one or two percent the size of Pluto. The trick was to find ones that are in orbits that the unmanned New Horizons spacecraft can reach with its remaining fuel.
According to NASA, the result of the search was a group of three candidates one billion miles (1.6 billion km) past Pluto, with two of the KBOs measuring about 34 mi (55 km) across and the third at 15 mi (25 km).
The US$650 million New Horizons mission was launched January 19, 2006 atop an Atlas V rocket from Cape Canaveral, Florida. The unmanned 478 kg (1,054 lb) spacecraft was sent on a 9.5-year mission to fly by Pluto – a distance so far that radio signals from the nuclear-powered probe take four hours to reach Earth. Sent on a slingshot trajectory using the gravitational pull of Jupiter, New Horizons is scheduled to pass the orbit of Neptune on August 24 and will rendezvous with Pluto on July 14 of next year, which it will pass at a distance of 13,000 km (8,000 mi).
If New Horizons' encounter with Pluto is successful, the team will submit a proposal to extend the mission, which will set the probe on a trajectory to fly by one of the candidate KBOs.
"We started to get worried that we could not find anything suitable, even with Hubble, but in the end the space telescope came to the rescue," says New Horizons science team member John Spencer of the Southwest Research Institute. "There was a huge sigh of relief when we found suitable KBOs; we are ‘over the moon’ about this detection."