48P/Johnson

 

This comet was discovered on August 15th 1949 by Ernest Johnson at Johannesburg, South Africa. It was magnitude 14 and very diffuse. It was found to be periodic with a period of 6.86 years and perihelion at 2.25AU. The comet is a rather undistinguished, highly evolved object, with a current perihelion distance of 2.31AU and period of 6.96 years.

 

The orbit is relatively stable, with relatively distant encounters with Jupiter (all 0.55-0.65AU) in 1931, 2014 and 2074 that lead to the perihelion distance ranging from the current 2.31AU down to 1.91AU, which it will have in 2078. At the same time, the period will range from 6.40 years (in 1929) to 6.97 (in 1997).

 

 

The comet was well covered at its 2004 return with a considerable amount of coverage from Ramón Naves & Montse Campàs (MPC 213), Miguel Camarasa (MPC 445), Julio Castellano (MPC 939), Francesc Baldris (MPC A01), Josep Lluis Salto (MPC A02), Cristavao Jacques (MPC I77), José Antonio Reyes & Sensi Pastor (MPC J76), Joaquín Sánchez (MPC J78) and Toni Climent (MPC J97). The light curve has reached  maximum well before perihelion at both the 1997 and 2004 returns according to Seichii Yoshida’s light curves, something that is clearly seen in the light curve (left).

 

In 2004 the light curve rose extremely quickly before perihelion with Yoshida finding a fit of 50 log r, as against the 15 log r fit to the 1997 apparition.

 

The data for Afrho shows a strong perihelion asymmetry, with a maximum of approximately 130-cm 80 days before perihelion, followed by a relatively rapidly decline to 50-cm at perihelion and 25-cm at T+80 days.