Southern Comet of 1947

Southern Comet of 1947
	The comet on 14 December 1947
Discovery
Discovery date	8 December 1947
Designations
Alternative designations	C/1947 X1, 1947 XII, 1947n
Orbital characteristics
Epoch	1947-Dec-19.0
Observation arc	25 days
Number of; observations	11
Aphelion	1,400 AU
Perihelion	0.110 AU
Semi-major axis	700 AU
Eccentricity	0.99984
Orbital period	18,500 years
Inclination	138.51°
Longitude of; ascending node	337.31°
Argument of; periapsis	196.18°
Last perihelion	2 December 1947
Earth MOID	0.255 AU
Comet total; magnitude (M1)	6.0

Last updated January 18, 2024

The Southern Comet of 1947 (also known with the designations C/1947 X1, 1947 XII, and 1947n) was a bright comet that became visible in the southern hemisphere in December 1947. At that point it was the brightest comet seen in two decades^[2] and is one of the brightest comets seen since 1935, with an estimated maximum apparent magnitude of -3.^[3]

Observational history

The comet passed from its perihelion on 2 December 1947, at a distance of 0.11 AU from the Sun, while closest approach to Earth was on 7 December, at a distance of 0.85 AU. The approach geometry was such that the comet could have been too faint to be discovered as it approached the Sun. After the first days of October, the comet approached rapidly the Sun and despite getting brighter, it was difficult to observe. On perihelion date, it is estimated that the comet was located 6 degrees at the Sun in the morning sky. Then it moved again in conjunction with the Sun and entered the evening sky.^[2]

The comet was discovered in evening twilight by many different observers on 8 December 1947, however there were unconfirmed reports from Cape Colony that it was spotted on 7 December. There is a report from Horsham, Australia, that the comet was seen in daylight about an hour before sunset. Harold Pallot, who taught astronomy in the local school, estimated the magnitude of the comet to be at least -5. The tail of the comet upon discovery was estimated by John Paraskevopoulos to be at least 25 degrees in length. The next day Paraskevopoulos estimated the magnitude of the comet to be +1.^[4]

Jorge Bobone, from the National Astronomical Observatory in Cordoba, Argentina, observed the comet telescopically on December 10 and noted that it had two nuclei 6.3 arcseconds apart.^[4] Zdenek Sekanina estimated that the nuclei were separated on 30 November 1947.^[5] On December 11 the comet reached its southermost declination, at -35°. By mid December, the comet was estimated to have a magnitude of 4 to 5, while Paraskevopoulos estimated it to be 2.5-3. The tail was estimated to be 1.5 degrees long, it was made of three components and appeared ragged. The two nuclei were about 10 arcseconds apart, as observed by Willem Hendrik van den Bos.^[4]

The comet continued to fade rapidly and was last seen by naked eye on 25 December,^[6] while by the end of the month its magnitude was estimated to be around 8. The nuclei were still observable, being about 17 arsceconds apart in a plate obtained on 31 December. The comet was last detected on 20 January 1948 by George Van Biesbroeck.^[4]

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References

↑ "Small-Body Database Lookup: C/1947 X1-A (Southern comet)". ssd.jpl.nasa.gov. Retrieved 19 August 2023.
1 2 Cunningham, Leland E. (1948). "THE BRIGHT SOUTHERN COMET, 1947 n". Publications of the Astronomical Society of the Pacific. 60 (352): 27–36. ISSN 0004-6280.
↑ "Brightest comets seen since 1935". www.icq.eps.harvard.edu. Retrieved 17 January 2024.
1 2 3 4 Kronk, Gary W. (2009). Cometography: a catalogue of comets. Cambridge: Cambridge University Press. pp. 276–281. ISBN 9780521585071.
↑ Sekanina, Zdenek (January 1978). "Relative motions of fragments of the split comets". Icarus. 33 (1): 173–185. doi:10.1016/0019-1035(78)90031-3.
↑ Bortle, John. "THE BRIGHT-COMET CHRONICLES". www.icq.eps.harvard.edu. Retrieved 19 August 2023.

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[jpl-1] "Small-Body Database Lookup: C/1947 X1-A (Southern comet)". ssd.jpl.nasa.gov. Retrieved 19 August 2023.

[Cunningham-2] 1 2 Cunningham, Leland E. (1948). "THE BRIGHT SOUTHERN COMET, 1947 n". Publications of the Astronomical Society of the Pacific. 60 (352): 27–36. ISSN 0004-6280.

[3] "Brightest comets seen since 1935". www.icq.eps.harvard.edu. Retrieved 17 January 2024.

[Cometography-4] 1 2 3 4 Kronk, Gary W. (2009). Cometography: a catalogue of comets. Cambridge: Cambridge University Press. pp. 276–281. ISBN 9780521585071.

[5] Sekanina, Zdenek (January 1978). "Relative motions of fragments of the split comets". Icarus. 33 (1): 173–185. doi:10.1016/0019-1035(78)90031-3.

[6] Bortle, John. "THE BRIGHT-COMET CHRONICLES". www.icq.eps.harvard.edu. Retrieved 19 August 2023.

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