Comet on collision course with earth

The Herald, October 26 1992 

A HUGE comet is on course to collide with earth on August 14, 2116, and could kill off most forms of life with an explosion more powerful than a million nuclear bombs, an expert on asteroids told a space conference yesterday. 

The 5 km-wide ball of ice and rock is travelling so fast that, if it does collide with earth full-on, it could plunge the world into the dark ages, astronomer Mr Duncan Steel of the Anglo-Australian Observatory told delegates in Sydney. 

“It would create an impact force of 20 million megatonnes, or about 1,6 million times the force of the bomb dropped on Hiroshima,” said Mr Steel, an authority on asteroids and leader of the world’s second biggest asteroid discovery team.

“Hopefully we personally are safe, our children are safe and even our grandchildren are safe, but it appears that our great-grandchildren are not safe,” he told the second Australian space development conference. 

The International Astronomical Union, the world astronomy authority, noted the comet’s discovery on October 15.

Named Comet Smith Tuttle, it was first sighted in 1862 and rediscovered in September this year. – Ziana-Reuter.

LESSONS FOR TODAY 

Comets are large prehistoric objects made of dust and ice that orbit the Sun. They are normally recognisable by their long, streaming tails. They are believed to be leftovers from the formation of the solar system 4,6 billion years ago.

Comets are sorted into four categories: periodic comets (e.g. Halley’s Comet), non-periodic comets (e.g. Comet Hale-Bopp), comets with no meaningful orbit (the Great Comet of 1106), and lost comets (5D/Brorsen), displayed as either P (periodic), C (non-periodic), X (no orbit), and D (lost).

Comet Swift-Tuttle is classified under periodic comet and it will take 133 years to orbit the Sun once. Swift-Tuttle last reached perihelion (closest approach to the Sun) in 1992 and will return again in 2125. 

While there were indications that Comet Swift-Tuttle will hit earth in 2125 Planetary Scientist Don Yeomans postulates that Earth faces no threat in 2126 although they may be a slight chance in 10 000 years. Part of that slim uncertainty, he says, is due to small influences on the comet that change its orbit ever so slightly each time it swings around the sun.