Also known as "old faithful", Encke was the second periodic comet in history whose orbit was determined and as a result, Encke was given the name of the calculator rather than the discoverer. Encke is a periodic comet with a very short run of only 3 years. It comes within Earths view (though not always able to be seen by the naked eye) in such a short period of time because unlike most comets, Encke only goes as far out as Jupiter. It is believed that it was created and spent most of its "youth" in either the Kuiper Belt or the Oort Cloud but somewhere along the line it was captured by Jupiters pull and remained within an orbit between the sun and Jupiter since.
Like Halley's comet, Encke was named after the individual who calculated its orbit, Johann Encke, rather than by its discoverer. The first recorded discoverer of Encke's comet was actually Pierre Méchain in 1786 but it was not identified as a periodic comet until Encke computed its orbit in 1819. It was through recordings of sightings of the comet from Caroline Herschel in 1795, Jean-Louis Pons in 1818, and many other independent sightings that led Encke to the realization it was a periodic comet.
Encke orbits the sun at a low inclination of 11.76° every 3.3 years which is the shortest of the reasonably bright comets but second shortest of overall comets, 311P/Panstarrs beats it at 3.2 years. Its orbit, from time to time, brings it within 25,894,000 km (16,090,000 mi) which is relatively close and it has close approaches to Earth roughly every 33 years.
Encke is in a relatively stable orbit between the sun and Jupiter but it is believed that it was originally formed in the Kuiper Belt. During its return towards the belt, Jupiter's gravitational pull prevented it from reaching its destination and it became locked in its current orbital path.
Encke is becoming fainter with each pass due to the loss of material. As it does not return to the Kuiper Belt, the loss of material is not replenished in some way and so it is diminishing with time. Its highest magnitude on record was 3.5 in 1829.
During ancient times, however, it was very bright and it is believed the symbol of the Swastika came from ancient astronomers view of the comet. In the Han Dynasty silk comet atlas, an image of a comet believed to be Encke is topped by this symbol. During a direct approach of this comet, its jets would curve creating this symbol.
Encke's nucleus is elongated and approximately 4.8 km (2.98 miles) in diameter. It rotates at an estimated 15-hour intervals as it orbits around the sun. As it orbits it leaves a dust trail behind that scientist believe is the cause of the seasonal meteor showers that we experience in November and June, Taurids and Beta Taurids.
In 1908, the Tunguska Meteorite leveled 2,150 square km (830 square miles) of trees in Siberia. It is believed that Encke may have been responsible for this. Scientist have concluded that the Tunguska Meteorite was, in fact, a broken off piece of Encke.
When describing the Tunguska event in 1908, it is often referred to as an airburst explosion with the equivalency of a multi-megaton nuclear blast. Many discussions have been held at scientific and governmental agencies hypothesis what would occur if Tunguska or any object of its size were to have hit a populated area such as a city. This brought into question safeguards against such events as well as preparation plans for handling such events.
Encke has given us the unique opportunity to observe the orbital patterns of comets. One observation that has been noticed from watching Encke is that comets do not orbit at a constant. Their speed accelerates and decelerates periodically. Another observation is that their orbital path changes slightly, moving closer to Earth some runs and moving further from Earth in others, due to the gravitational pull of surrounding bodies. Jupiter is the biggest contributor of this with its high gravitational influence.
Encke was last seen on November 21, 2013, and is due to return on March 10, 2017. It is predicted to be well visible from our northern hemisphere but not without the aid of a telescope. It will brighten as it draws closer but would still not be able to be seen properly by the naked eye but is possible to be seen through binoculars at that point. It will be within our southern hemisphere by the time it begins to move out of the inner solar system and out of Earths view again.
- Comet Encke's tail ripped by the Sun
- Solar Hurricane Tears Off Tail of Comet Encke
- Taurids and meteorites: fragments from comet Encke