4 May 2018
Perihelion Distance (q)
Aphelion Distance (Q)
Click for NASA orbit diagram
Hills Observatory: 1 January 2013 to 19 January 2019
Alexander F. I. Forbes (Rosebank, South Africa) discovered this comet in Microscopium on 1
August 1929. He estimated the magnitude as 11. Forbes informed astronomers at Johannesburg,
but no announcement was made until they confirmed the comet on 3 August.
Since the comet was already passed its perihelion and closest distance from Earth (0.55 AU on
15 July) it faded following it 1929 discovery. It reached magnitude 14 as October began and was
near 15 at the beginning of November. George van Biesbroeck (Yerkes Observatory, Wisconsin,
USA) was the final observer when he saw the comet at magnitude 16.5 on 11 November.
Frederick Richard Cripps and Hans Q. Rasmusen independently provided orbits for the 1935.
Unfortunately, the comet was not favorably placed, as the comet would be close to the sun
when at its brightest.
The comet was recovered at its 1942 apparition by Van Biesbroeck, on a 20-minute exposure
obtained with the 24-inch reflector on 15 June. Van Biesbroeck said the comet appeared on the
two plates as a 15th-magnitude object exhibiting a tail extending about 1 arc minute in PA 270
degrees. The comet apparently reached 12th magnitude during July, and then faded and was
last seen by van Biesbroeck at McDonald Observatory on 5 October.
The comet was again recovered on 14 May 1948, and brightened to magnitude 14.5 during
September. The comet was last detected on 2 October. The 1955 apparition was again not very
favorable and no observations were made.
The comet's 4th observed apparition came in 1961. Elizabeth Roemer (U. S. Naval Observatory,
Flagstaff station, Arizona, USA) recovered the comet on a 120-minute photograph exposed on
16 January. The magnitude of the condensed image was determined as 20.2, but as only one
photograph was obtained, it was only suspected of being 37P/Forbes. An opportunity for Roemer
to confirm the recovery did not come until 13 February, when images were found on a pair of
plates. The comet reached a maximum magnitude of 10 during July and then faded and was
last detected on 5 December. The nucleus was then estimated as magnitude 19.8. The 1967
apparition was again unfavorable. Numerous searches were made during the period of March
through November, but without success.
The comet has been seen at every return since 1974. Prior to the 1999 apparition, the best
returns were those of 1974 (magnitude 13) and 1993 (magnitude 14). The comet seemed to be
heading for another normal apparition in 1999, when it attained its predicted total magnitude of
13 at the end of May and early in June. Then the comet seemed experienced an outburst around
mid-June, when observers began reporting a brightness of magnitude 11, if not slightly brighter.
As the comet moved away from both the sun and Earth, it finally faded back to 13 by early
September and was near 14 around mid-October.
Close approaches to planets:
0.55 AU from Earth on 16 July 1929 (contributed to comet's discovery)
0.58 AU from Earth on 25 June 1961
0.83 AU from Earth on 14 August 1974
0.37 AU from Jupiter on 30 August 1990 (decreased perihelion distance from 1.47
AU to 1.45 AU and decreased orbital period from 6.26 to 6.13 years)
0.56 AU from Jupiter on 17 October 2001 (increased perihelion distance from 1.45
AU to 1.57 AU and increased orbital period from 6.13 to 6.35 years)
0.67 AU from Earth on 20 June 2005
0.98 AU from Earth on 18 August 2018
0.95 AU from Earth on 30 May 2037
0.70 AU from Earth on 22 June 2050
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