Comet 5D/Brorsen Saturday, June 27, 2009

5D/Brorsen

Discovery
Discovered by:	Theodor Brorsen
Discovery date:	26 February 1846
Alternate designations:	1846 III; P/1846 D2; 1857 II; P/1857 F1; 1868 I; 1873 VI; 1879 I
Orbital characteristics A
Epoch:	March 31, 1879 [1]
Aphelion distance:	5.610 AU
Perihelion distance:	0.5898 AU
Semi-major axis:	3.100 AU
Eccentricity:	0.8098
Orbital period:	5.461 a
Inclination:	29.382°
Last perihelion:	March 31, 1879
Next perihelion:	Lost

5D/Brorsen (also known as Brorsen's Comet or Comet Brorsen) is a comet discovered February 26, 1846, by the Danish astronomer Theodor Brorsen.

The perihelion of 5D/Brorsen was February 25, just a day before its discovery, and maintained the approach to Earth after that, passing closest to Earth on March 27 (at a distance of 0.52 AU). As a result of this close encounter to Earth the comet's coma diameter increased. Johann Friedrich Julius Schmidt estimating it as 3 to 4 arcmin across on March 9, and 8 to 10 arcmin across on the 22nd of that same month. Last seen on April 22, it was stationed about 20 degrees from the north celestial pole. By the end of this first apparition the orbital period was identified as 5.5 years. It was discovered that a close approach to Jupiter in 1842 put in its discovery orbit.

The comet's 5.5 year period would mean that apparitions would alternate between good and poor. As expected, the comet was missed in its 1851 apparition, when the comet only came as close as 1.5 AU to earth.

The comet's orbit was still pretty uncertain, made worse by the fact it had approached Jupiter in 1854. In 1857, Karl Christian Bruhns found a comet on 18 March 1857. Soon an orbit was computed and it was found to be 5D/Brorsen, although predictions were three months off. The comet was followed until June 1857.

The comet was missed in 1862, and the next recovery was in 1868. A close approach to Jupiter shortened the period enough to make the comet visible in 1873. A very favorable apparition followed in 1879, allowing the comet to be observed for the longest time to date – four months. The comet was missed in 1884, due to observing circumstances, but was also missed in 1890, a favorable apparition. The next favorable apparition occurred in 1901, but searches did not locate the comet.

The next serious search was started by Brian Marsden, who believed the comet had faded out of existence, but computed the orbit for a very favorable 1973 apparition. Japanese observers made intensive searches for the comet, but nothing turned up. The comet is currently considered lost (see lost comet).