Two asteroids to narrowly miss Earth

By Heather Catchpole 8 September 2010
Reading Time: 2 Minutes Print this page
Two asteroids on different orbits will zoom close to Earth, within hours of each other.

TWO PREVIOUSLY UNIDENTIFIED ASTEROIDS will swing by the Earth tonight, approaching to within a fraction of the distance between the Earth and the Moon.

The two asteroids, dubbed 2010 RX30 and 2010 RF12, were discovered on Monday by astronomers at the Mount Lemmon Observatory in Arizona, USA as part of the Catalina Sky Survey, which scans the skies for near-Earth objects.

Australian astronomer Nick Lomb, curator-at-large of astronomy at the Sydney Observatory says it’s unusual to have two objects pass this close to the Earth within a few hours of each other. “There are asteroids passing this close to Earth on a regular basis, but having two, and two that have been discovered in advance, is very unusual,” he told Australian Geographic.

2010 RF12 will pass 79,000 km above the Earth, one-fifth the distance between the Earth and the Moon, making its closest approach while over Antarctica at 7.12 a.m. AEST tomorrow morning. NASA estimates the asteroid is between six to 14 metres in size.

2010 RX30 is larger at 10 to 20 m wide and on a different orbit. At its closest point it will approach to 248,000 km above the North Pacific Ocean, south of Japan, at 7:51 p.m. AEST tonight.

Nick says 2010 RF12 would be the best bet to spot as it will be visible through the night, before making its closest approach tomorrow morning – but it will still be very faint. At about magnitude 14, the asteroid is 1600 times fainter than anything that could be seen with the naked eye. But it should still be visible to medium-sized telescope.

50 million undiscovered asteroids

NASA’s Jet Propulsion Laboratory estimates there are about 50 million undiscovered asteroids and comets of this size and one will pass within lunar distance (the distance between the Earth and Moon) almost every day, although not all of them are discovered.

Each decade an asteroid about 10 m wide generally strikes the Earth’s atmosphere. These asteroids are typically blown to pieces by their encounter with the atmosphere and never reach the Earth.

Siding Springs picks up 100-200 of these objects each year and their ability to spot smaller objects is improving, says Donna Burton, a senior technical officer from Siding Spring Observatory in Coonabarabran in NSW, the Southern Hemisphere partner of the Catalina Sky Survey.

“The advent of space based missions have made it easier to find these smaller fainter objects,” she says. “I’ll be going out tonight to take a look with binoculars but I think it will be a bit of a challenge.”  The asteroids will look like a faint satellite moving quickly and if it was to hit atmosphere would look like a shooting star as it burnt up, she adds.

Amateur astronomers will need a telescope with an aperture from at least 30 to 40 cm and should use at least a 20 to 30 second exposure to catch the object, which is moving rapidly, Nick says. Information on the exact location of both asteroids using the International Astronomy Union’s Minor Planet Centre website.

Catalina Sky Survey