Two months ago, a boulder-sized object smashed into the surface of the Moon. The resulting flash — which could be seen by the naked eye — was 10 times brighter than anything witnessed before.
The Moon is hit by meteoroids all the time, but this impact was particularly notable. Looking at it from Earth, the one-second flare-up would have had the same intensity as a 4th magnitude star.
The meteoroid is estimated to have been about 40 kg and about 0.3 to 0.4 meters wide. But because it was traveling at 56,000 mph — and with no atmsophere to slow its descent — it resulted in an explosion equivalent to five tons of TNT.
An interesting question to ask is, if the Moon has no oxygen, how can something explode? NASA explains:
Lunar meteors don't require oxygen or combustion to make themselves visible. They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.