Comet 1P/Halley can be observed from Earth once every 75-76 years and is probably the most well known ‘household name’ comet known as Halley’s Comet. The reason for this is it is the brightest short period comet that regularly visits the solar system and the only short period comet that is so clearly visible to the naked eye on each passage. The image above taken by NASA was from Halley’s last visit in 1986. It was during this passage that it was the first to be observed by a spacecraft which provided vital data on the structure and behavior of a comet nucleus, coma and tail. There are records of Halley’s Comet dating back as far as 240BC. There are historic records from the ancient Chinese, Babylonion and medieval Europeans alike of the comet which can be accurately matched to Halley’s back-dated orbits.
The 1986 Apparition
The comet’s closest approach in 1986 was the first time that spacecraft were sent up close to a comet to observe a comet’s nucleus in detail. However, for observers on the ground, the 1986 apparition was one of the worst viewing circumstances for viewing Halley’s comet. This was due to the comet’s position relative to Earth (opposite sides of the Sun). The point at which the comet reached its brightest was when the famous object was closest to the Sun as viewed in the sky. Many observers in urban areas did not get a decent view of the comet as light pollution washed out the tail. Some observers in more rural areas got a good view with binoculars and telescopes over the nights when it was a little further from the Sun.
Despite the unfortunate position of the Comet, photographers were also able to get some nice shots like the image above taken over Penshaw monument, Sunderland by Gordon Percival (a founder and long serving member of South Shields Astronomical Society).
The Comet’s Name
The comet’s orbital period was first discovered by an English astronomer by the name of Edmund Halley in 1705 which why now the comet is crowned its famous name. He examined reports of a comet approaching Earth in 1531, 1607 and 1682. He concluded that these three comets were actually the same comet returning to the solar system in an orbit, and predicted the comet would come again in 1758 and of course, when the time came his theory was vindicated despite him not living to see the event for himself and the comet was named after him.
Comet Halley’s next apparition
Just like Edmund Halley’s clockwork predictions, Comet Halley will return again in the year 2061 with perihelion occurring on 28th July that year. It will be better placed for observation compared to that of the 1986 appearance and is expected to reach visual magnitude -0.3.
Comet Halley’s orbit comes close to Earth’s in two places. For this reason, Halley is the parent body of two meteor showers as viewed from Earth: the Eta Aquariids in early May, and the Orionids in late October. Observations conducted around the time of Halley’s appearance in 1986, however, suggest that the Eta Aquarid meteor shower might not originate from Halley’s Comet but may well be perturbed by it.