Saturday, January 31, 2009

Unknown planet in an uncertain universe

OK its confession time in regard to what we know about the known universe. We don't know where all the bits are. Lurking in the solar system's dark recesses, is an undiscovered world - Planet X, a frozen body perhaps as large as Mars or our own dear Earth.

The discovery of new planets in the solar system would be one of the most significant addition to the solar system since the discovery of Pluto in 1930. Eeven now, pluto is still fueling a planet v non-planet debate. When the International Astronomical Union voted to downgrade Pluto to dwarf planet status in 2006, they established three criteria for a bone fide 'planet' in our solar system:
  • it must orbit the sun;
  • its gravity must suffice to mould it into a near-spherical shape; and
  • it must be massive enough to have ploughed its orbit clear of other bits and bobs.
Unfirtunately Pluto failed to make the cut. It falls down on this third point. It is just one of many objects that are contained within the Kuiper belt (KBOs). These are icy bits of debris that pepper space from Neptune's orbit at 30 astronomical units out to around 50 AU. (1AU = the distance between Earth and our sun)

Any new object would have to be well clear of the Kuiper belt to qualify as a planet. Yet intriguingly, it is studies of the belt that have suggested planet X's existence. Some KBOs travel in extremely elongated orbits around the sun. Others have steep orbits almost at right angles to the orbits of all the major planets. It was surmised that these could be signs of perturbation from a massive distant object, says a solar system scientist at the University of Hawaii.

That is by no means a general consensus. An early, slow outward migration of the giant planets could also explain some of these strange KBO orbits - although it has difficulty explaining all of the belt's observed properties and anomolies.

Over the past 20 years, huge swaths of the sky have been searched for slowly moving bodies, and well over 1000 KBOs found. But these wide-area surveys can spot only large, bright objects; longer-exposure surveys that can find smaller, dimmer objects cover only small areas of the sky. A Mars-sized object at a distance of 100 AU or more, would be so faint that it could easily have escaped detection.

That could soon change. In December 2008, the first prototype of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) was brought into service at the Haleakala observatory on Maui, Hawaii. Soon, four telescopes - equipped with the world's largest digital cameras, at 1.4 billion pixels apiece - will search the skies for anything that blinks or moves. Its main purpose is to look out for potentially hazardous asteroids on a collision course with the Earth but other space objects and spurious inhabitants of the outer solar system should not escape its all-seeing eyes.

The discovery of a further planet would be thrilling. One of the possible explanation for its presence there would be that large bodies coalesced very early in the solar system's history, only to be ejected by the gravity of the giant planets later on. That would firm up ideas about how the solar system has developed and greater insight into its more distant recesses.

To read the full story follow this link; Planet-X

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