Newly discovered asteroid 2003 QQ47 has received considerable media attention over the last few days because it had a small chance of colliding with the Earth in the year 2014 and was rated a “1” on the Torino impact hazard scale, which goes from 0 to 10. The odds of collision in 2014, as estimated by JPL’s Sentry impact monitoring system, peaked at 1 chance in 250,000, a result which was posted on our Impact Risk Page on Saturday, August 30. Impact events at the Torino Scale 1 level certainly merit careful monitoring by astronomers, but these events do not warrant public concern. In fact, each year several newly discovered asteroids reach Torino Scale 1 for a brief period after discovery; 2003 QQ47 is the fourth such case this year.
As astronomers continue to monitor an asteroid and measure its position, more precise predictions can be made. On September 2, new measurements of QQ47’s position allowed us to narrow our prediction of its path in 2014, and thus we could rule out any Earth impact possibilities for 2014. In our Impact Risk Page for 2003 QQ47, the entry for the year 2014 has now disappeared, although a number of potential impact events remain for later years. We expect that these too will be ruled out in the coming days as astronomers continue to track the object and we refine our orbit predictions.
These seemingly large day-to-day changes in impact predictions for newly discovered asteroids are just what we expect. In the few days after an asteroid is first discovered, its orbit is known only very approximately. The range of possible positions in future years is wide and can easily encompass the Earth, but as the object continues to be tracked, the range of possibilities shrinks quickly, allowing us to rule out any possibility of impact. This process is ongoing for 2003 QQ47, and could take days or even weeks before all potential impacts are ruled out.