View article

The asteroid (3200) Phaethon is widely recognized as the parent of the Geminid meteoroid stream. However, it has never shown evidence for ongoing mass loss or for any form of comet-like activity that would indicate the continued replenishment of the stream. Following an alert by Battams & Watson, we used NASA's STEREO-A spacecraft to image Phaethon near perihelion, in the period UT 2009 June 17–22, when the heliocentric distance was near 0.14 AU. The resulting photometry shows an unexpected brightening, by a factor of two, starting UT 2009 June 20.2±0.2, which we interpret as an impulsive release of dust particles from Phaethon. If the density is near 2500 kg m− 3, then the emitted dust particles must have a combined mass of∼ 2.5× 10 8 a 1 kg, where a 1 is the particle radius in millimeters. Assuming a 1= 1, this is approximately 10− 4 of the Geminid stream mass and to replenish the stream in …