2004 AS1

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2004 AS1 (also written 2004 AS1), also known by the temporary name AL00667,[1] is an Apollo-class near-Earth asteroid, first discovered on January 13, 2004, by the LINEAR project. Based on the asteroids brightness and assumed proximity to Earth, the asteroid was originally estimated to be only 30 meters in diameter.[2]

Although rather ordinary, it caused some controversy in astronomical circles due to initial projections posted on the web by the Minor Planet Center (MPC) suggesting an imminent collision with Earth on or about January 15 with a likelihood of 1:4.[1] These projections came from very early observations, and turned out to be 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 Earth on 16 February 2004 at a distance of 0.08539 AU (12,774,000 km; 7,937,000 mi)[3] (or 33 times the distance from Earth to the Moon), posing no threat. It is an Apollo asteroid, with perihelion at 0.88 AU, a rather low eccentricity of 0.17, an inclination of 17° and an orbital period of 1.11 years.[3]

With an absolute magnitude (H) of 20.5,[3] the asteroid is now known to be around 210–470 meters (690–1,540 feet) in diameter, depending on the albedo (the amount of light it reflects).[4]


  1. ^ a b "2004 AS1 (When initial predictions go wrong...)". Great Shefford Observatory. Retrieved 2014-02-25.  archive
  2. ^ "Earth almost put on impact alert". BBC News. 2004-02-24. Retrieved 2014-02-25. 
  3. ^ a b c "JPL Small-Body Database Browser: (2004 AS1)". Jet Propulsion Laboratory. 2014-02-06 last obs (arc=10 yr). Retrieved 2014-02-25. 
  4. ^ "Absolute Magnitude (H)". NASA/JPL. Retrieved 2014-02-25.