2004 AS1 (also written 2004 AS1), also known by the temporary name AL00667, is a near-Earthasteroid, first discovered on January 13, 2004, by the LINEAR project.
Although rather ordinary, it caused some controversy in astronomical circles due to initial projections posted on the web by the Minor Planet Center suggesting an imminent collision with Earth on or about January 15 with a likelihood of 1:4. These projections came from very early observations, and turned out to be quite inaccurate (which is an ordinary occurrence in astronomy, as new observations refine the projected path of an object). In fact, the poster at the MPC had not realised that the data he had posted was essentially an impact prediction.
The general media did not get hold of the story at the time.
The asteroid passed at a distance of 12 million km (or 32 times the distance from the Earth to the Moon), posing no threat. It turned out to have a diameter of about 500m. It is an Apollo asteroid, with perihelion at 0.88AU, a rather low eccentricity of 0.17, an inclination of 17° and a orbital period of 1.11 years.
External links
Great Shefford Observatory page on 2004 AS1 (http://www.birtwhi.demon.co.uk/Gallery2004AS1.htm)
BBC story (http://news.bbc.co.uk/2/hi/science/nature/3517319.stm)
The asteroid, now designated 2004AS1, was not a planet killer, like the one that caused the extinction of the dinosaurs 65 million years ago, or even a city killer.
Believed at the time to be about 100 feet across, 2004AS1 would most likely have exploded with the force of a one-megaton bomb several miles up in the atmosphere.
Subsequent observations showed that 2004AS1, which came no closer than 7 million miles to Earth, is in no danger of hitting Earth in the next century.
Some scientists believed on 13 January that a 30m object, later designated 2004AS1, had a one-in-four chance of hitting the planet within 36 hours.
Designated 2004 DW, it was found on 17 February by an automated sky survey telescope in California.
2004 DW was found by California Institute of Technology astronomers Chad Trujillo and Mike Brown, and David Rabinowitz of Yale University, the same team that discovered Quaoar in 2002.
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