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Tuesday 6 April 2004

Earth-threatening space rocks hunted by ANU

Astronomers using a refurbished telescope at the ANU Siding Spring Observatory have discovered two Near-Earth Asteroids (NEA’s).

The search for space rocks on a collision course with Earth is usually the preserve of Northern Hemisphere astronomers, but the renovation of the 0.5-metre Uppsala Schmidt telescope has enabled Siding Spring researchers to start hunting NEA’s –  asteroids that pass near the Earth and may pose a threat of collision.

Siding Spring Survey (SSS) astronomer Mr Gordon Garradd has detected two asteroids - one roughly 100-metres in diameter  and another roughly 300-metres wide. SSS partner Dr Robert H. McNaught confirmed both discoveries in images he took with the Siding Spring 1-metre telescope that same night.

The 100-meter asteroid, named 2004 FH29, makes a complete orbit around the sun every 2.13 years. Today it will miss Earth by three million kilometres (eight times the distance between Earth and Moon) travelling at 10 km per second relative to Earth.

The 300-meter asteroid, named 2004 FJ29, orbits the Sun about every 46 weeks. It came within 21 million kilometres of Earth last Tuesday, 30 March 2004, travelling at 18 km per second relative to Earth.

Neither object poses a direct threat of colliding with Earth.

Had the asteroids not missed, damage from their impacts would have depended on what they're made up of – for example ice, rock, or iron. A 100-metre object would be likely to mostly burn up in Earth's atmosphere, but a 300-metre object would probably reach Earth's surface where it could do some damage, the researchers say.

The new survey is a joint collaboration between the ANU Research School of Astronomy and Astrophysics and the University of Arizona Lunar and Planetary Laboratory and is funded by NASA's Near-Earth Object Observation Program.

When astronomers detect what they suspect is an NEA, they immediately must take additional images to confirm their discovery, Dr McNaught said. Surveys often have to suspend their NEA searches and spend observing time confirming NEA, or they risk losing them altogether because follow-up observations were made too late, he added.

The SSS plan is to use a 40-inch telescope to quickly confirm suspect asteroids detected with the Uppsala, freeing the smaller telescope to continue its searches.

"Our confirmation strategy worked beautifully on our first try," Dr McNaught said.

Dr McNaught and Mr Garradd will operate SSS about 20 nights each month. They suspend operations when the week around full moon brightens the sky, making faint object detection difficult.

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