Tag Archives: NEA

A 100-foot diameter newly discovered asteroid will zip past the Earth inside the Moon’s orbit today at 4:07 pm Eastern.

Chicken Little report: A 100-foot diameter newly discovered asteroid will zip past the Earth inside the Moon’s orbit today at 4:07 pm Eastern.

The asteroid, dubbed 2014 DX 110, is about 100 feet in diameter and is set to come within 216,000 miles of Earth — a close shave by astronomical standards, considering our Moon orbits the Earth at a distance of about 238,900 miles.

While an object that size may not seem imposing, if it were to strike the Earth, it would release a devastating amount of energy greater than a nuclear weapon. The infamous asteroid that exploded over Tunguska, Siberia, on June 30, 1908, has been estimated to be about 30 meters to 60 meters — 100 feet to 200 feet — in diameter.

While it is true that the impact would be significant, this news report does the typical fear-mongering to make the story seem interesting. The problem, however, is that the detection of these fly-bys is becoming more frequent. The number of asteroids isn’t changing, but our ability to spot them is, and with more frequent discoveries comes more frequent news stories like this. I fear that such stories — fueled by press releases from various astronomy organizations — are going to begin to sound like a kid “crying wolf” to the general public. The threat from an asteroid impact is real, even if most asteroids miss us. Desensitizing the public to the threat is not a good thing.

New data has allowed scientists to lower the chance that the asteroid Apophis will hit the Earth in a future orbit.

New data has allowed scientists to lower the chance that the asteroid Apophis will hit the Earth in a future orbit.

Recent observations from Pan-STARRS PS1 telescope at Haleakala, Hawaii have reduced the current orbital uncertainty by a factor of 5, and radar observations in early 2013 from Goldstone and Arecibo will further improve the knowledge of Apophis’ current position. However, the current knowledge is now precise enough that the uncertainty in predicting the position in 2029 is completely dominated by the so-called Yarkovsky effect, a subtle nongravitational perturbation due to thermal re-radiation of solar energy absorbed by the asteroid. The Yarkovsky effect depends on the asteroid’s size, mass, thermal properties, and critically on the orientation of the asteroid’s spin axis, which is currently unknown. This means that predictions for the 2029 Earth encounter will not improve significantly until these physical and spin characteristics are better determined.

The new report, which does not make use of the 2013 radar measurements, identifies over a dozen keyholes that fall within the range of possible 2029 encounter distances. Notably, the potential impact in 2036 that had previously held the highest probability has been effectively ruled out since its probability has fallen to well below one chance in one million. Indeed only one of the potential impacts has a probability of impact greater than 1-in-a-million; there is a 2-meter wide keyhole that leads to an impact in 2068, with impact odds of about 2.3 in a million.

The second paragraph basically says that the keyholes that might bring Apophis back to Earth are very small, making it unlikely that the asteroid will fly through any one of them in 2029. The first paragraph however notes that it will be impossible to chart the asteroid’s course accurately enough to rule out this possibility until we have more data on the asteroid itself.