This comet was discovered on August 26th 1948 by Joseph Ashbrook from Lowell Observatory in Arizona where he was observing. Ashbrook was a Yale astronomer and, by a curious coincidence, twelve hours later the comet was independently discovered from the Yale-Columbia station in South Africa by Cyril Jackson.
The comet currently has a period of 7.46 years with perihelion at 2.31AU. However, over the last 100 years the orbit has changed radically. A moderately close encounter with Jupiter in 1929 increased the perihelion distance from 3.79AU to 4.05AU. A close encounter with Jupiter (0.18AU) on June 22nd 1945 then reduced it to 2.31AU, making the comet a relatively easy target at its discovery apparition. A further encounter with Jupiter in 2001 has though increased the perihelion distance to 2.80AU so that the comet will be significantly fainter at its next apparition in 2009. A further close approach in 2064 will decrease the perihelion distance once more, back to 2.42AU.
The 2001 apparition was the seventh observed return to perihelion. The comet has an extremely rapid rate of brightening and fade with heliocentric distance. Seichii Yoshida finds 23 log r pre-perihelion and 28 log r post-perihelion. The light curve (left) is based on seven nights of observations by Pepe Manteca at Begues (MPC 170) and one night by Ramón Naves and Montse Campàs at MontCabrer (MPC 213), plus a total visual magnitude estimate by Carlos Segarra.
The observations suggest that there may have been an important perihelion asymmetry, with the greatest activity advanced with respect to perihelion. This is also suggested by Seichii Yoshida’s light curve. The highest measured value of Afrho, some five months before perihelion, was 60-cm, although the lack of observations close to perihelion limits the conclusions that can be obtained. The data also suggests that this is a very gassy comet with a large gas to dust ratio.