While the eyes of much of the world were trained on the Moon during January’s lunar eclipse an attention-seeking bit of space debris made an appearance, creating a flash observed from Morocco to California. Now astronomers have revealed the nature of the object in question, including its speed, size and the crater it left behind.
Objects large enough to produce craters hit the Moon quite often. Similar objects burn up in the Earth’s atmosphere frequently, after all. Lacking such protection, the damage these objects do to the lunar surface is visible through any telescope.
However, January 21 this year was the first confirmed record of a meteor strike occurring during a lunar eclipse. In the Monthly Notices of the Royal Astronomical Society, the University of Huelva's Professor Jose Maria Madiedo reports the flash from the impact lasted 0.28 seconds, peaking with the brightness of a magnitude 4.2 star – easily visible under dark conditions if you were looking in the right place, even without equipment.
Based on the brightness at different wavelengths of light Madiedo concludes ejected materials reached a temperature of 5,700 Kelvin (9,800 ºF), which by sheer coincidence equals that of the Sun's surface.
The authors predict a crater diameter of between 10 and 15 meters (33-50 feet) depending on the density of the impactor. This is far too small to be picked up by Earth-based telescopes, but it may be possible to find it by comparing photographs taken by lunar orbiters before and after the event.
The impact speed was calculated at 17 kilometers per second (61,000 km/h or 38,000 miles per hour), and the mass estimated at 45 kilograms (100 pounds). The energy released was equivalent to 1.5 tons of TNT. If you ever think you’re too small to make a difference in the world, remember that something that probably weighs less than you was seen by the entire world, although admittedly it was traveling rather fast to do it.
Many of Earth's meteors come from showers, which in turn can be traced back to the break up of specific comets. However, the paper reports everything we know about the timing and location of this impact is inconsistent with any known meteor shower, leading the authors to claim 99 percent confidence this was a “sporadic” object whose origins can’t be identified.
“Observing flashes is a great way to test our ideas on exactly what happens when a meteorite collides with the Moon,” Madiedo said in a statement.
A second flash was also reported by the Royal Observatory in Greenwich, but none of the other cameras trained on the Moon at the time picked it up. Consequently, the authors believe it is more likely to represent light reflecting from a passing satellite or a cosmic ray than a second meteorite strike.