JUNK from outer space is to come raining down tomorrow, giving Hong Kong its best light show for many years. Thousands of bits of debris left by a passing comet will be burned up in the atmosphere as the Earth moves through the heavenly rubbish. Single meteors, or shooting stars, are fairly common, but it is rare to have so many hitting the atmosphere at once or for so long. The meteor shower may last up to two days and, at its peak - expected to be between 1 am and 4 am tomorrow - a dozen pieces of rock could be smashing into the atmosphere every minute. No telescopes or special equipment will be needed to see the show, which will take place near the Perseus constellation, in the northeastern sky. However, bad weather could ruin the view. The Perseus constellation is roughly triangular with a tail that should be visible at an elevation of between 18 and 53 degrees from the horizontal. A Royal Observatory spokesman said: ''Meteors are small particles moving in orbit around the sun. They occasionally intercept the Earth. When one hits the atmosphere at high speed, the air resistance quickly heats up the particle to give out light. ''On some nights, a cluster of meteorites appears to produce what is known as a meteor shower.'' Hong Kong University physicist and amateur astronomer Dr Chau Hoi-fung said: ''Everyone should be able to see it, if the weather permits. ''This one will be quite special because there will be so much happening at once.'' Few, if any, of the meteors will make it through the atmosphere. According to the Royal Observatory spokesman, the particles are small and usually burn up, posing little danger to anyone on the ground.