42P/Neujmin 3


This comet was discovered as a magnitude 13 object by Neujmin in Crimea on August 2nd 1929, once again in the course of his asteroid survey programme. With a 10.9 year period, which has reduced slightly thanks to Jupiter encounters, to 10.7 years the 2004 return should have been its seventh since discovery, however, those of 1940, 1961 and 1982 were missed. This is an instrinsically faint object with low activity and with perihelion at 2.01AU it is often a very faint object.


A close encounter (0.112AU) with Jupiter in 1836, followed by a further, more distant one in 1852 reduced the perihelion distance from 2.75AU to 2.18 and then to 2.03, making it more easily observable. By the end of the 21st century further encounters with the Earth and Jupiter will progressively reduce the perihelion distance to 1.83AU.



The 2004 return was almost the best possible with the comet almost exactly at opposition at  perihelion. This led to the comet having a rather flat light curve over the months around perihelion as the comet almost tracked the Earth in its orbit.


The activity was low, even at perihelion, with a peak value of Afrho of 40-cm. There was a small perihelion asymmetry with the peak value of the dust emission activity about 1 week before perihelion.