C / 1807 R1 (Great Comet)
| C / 1807 R1 (Great Comet) [i] | |
|---|---|
| Properties of the orbit ( animation ) | |
| Orbit type | long-period |
| Numerical eccentricity | 0.9955 |
| Perihelion | 0.646 AU |
| Aphelion | 285.8 AU |
| Major semi-axis | 143.2 AU |
| Sidereal period | ~ 1714 a |
| Inclination of the orbit plane | 63.2 ° |
| Perihelion | September 19, 1807 |
| Orbital velocity in the perihelion | 52.3 km / s |
| history | |
| Explorer | Parisi |
| Date of discovery | September 9, 1807 |
| Older name | 1807 |
| Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles . | |
C / 1807 R1 was a comet that could be seen with the naked eye in 1807 . Due to its brightness and long tail, it is counted among the " Great Comets ".
Discovery story
Due to its visibility, this comet should have been discovered first in the southern hemisphere , several weeks before it was actually found, but there are no reports from there. In Australia the comet would have been visible on the western horizon in early dusk throughout August 1807 , because its brightness increased steadily up to 1 mag .
The actual discovery is therefore attributed to Parisi on Castrogiovanni , who saw the comet just above the horizon at dusk on September 9, 1807, not far from the equally bright Spica (α Virginis). It must have been a magnificent sight because Venus , Mars, and Saturn were also nearby in the sky. The southern location of the observer was advantageous over other astronomers in Europe and elsewhere who made their independent discoveries a few days later.
The surveyor Seth Pease saw the comet during its exploration of the Mississippi River in the United States on the evening of September 20 (local time). The following evening Jean-Louis Pons saw him in Marseille and his colleague Jacques-Joseph Thulis was able to carry out a first position determination. In the following 10 days there were further discoveries by Jacques Vidal and Honoré Flaugergues in France, Edward Pigott in England, Johann Sigismund Gottfried Huth and Johann Friedrich Eule in Germany and Gonzalez in Spain . Vidal saw the comet with a 7–8 ° long tail .
Further observations
Towards the end of September the comet moved away from the sun and earth again , but could still be followed with open eyes throughout October . On October 1, Johann Elert Bode saw a 5 ° long tail, while Huth reported on October 4 that the tail had split into two components: a more than 6 ° long, straight tail and a shorter, curved one (based on current knowledge presumably Plasma and dust tail ). Both could still be seen on October 20, when Heinrich Wilhelm Olbers noted that they were 1.5 ° apart: the northern one very narrow, thin, straight and about 10 ° long, the southern short, wide and lighter with 4, 5 ° longitude. A few days later, the two tails were no longer distinguishable from each other, William Dunbar in Natchez saw a tail 2.7 ° in length on October 24th. The Göttingen astronomer Hieronymus Schröter achieved an excellent series of measurements from his observations from October 4, 1807 to February 18, 1808.
Even in November and December the comet was still an object to the naked eye, but its brightness decreased and its tail became inconspicuous. Wilhelm Herschel estimated its length to be 2.5 ° on November 20, at the beginning of December he could only see a short tail in a large refractor .
From January 1808, no more reports of free-eyed observations of the comet are available; on January 6, Dunbar only saw it with the telescope. The last telescopic sightings were made on February 19th by Olbers, on February 24th by Friedrich Wilhelm Bessel and on February 26th after a long search by Dunbar . The last observer was Vincent Wisniewsky in Saint Petersburg on March 27, 1808.
The comet reached its maximum brightness of 1 to 2 mag on September 20th.
Scientific evaluation
As early as October 1807, the first parabolic orbits for the comet were calculated by Bode, Johann Karl Burckhardt and Francis Triesnecker . Bessel initially also calculated a parabolic, but after further observation data were available, the parameters of elliptical orbits . Since this still did not agree with the observations to his satisfaction, he developed a new calculation method for the orbital elements , which also took into account the changing gravitational influences of the sun and the other planets during the passage of the comet through the inner solar system and the precision of the individual observation data by weighting according to the method of least squares developed by Carl Friedrich Gauß a few years earlier .
Since observation data for this comet was available for six months and thus for a significant part of the comet's orbit, the extremely precise correspondence of Bessel's calculations with the observations could easily be checked. This was the first mathematical proof that a comet (in addition to Halley's comet , for which it was already known through observation of its regular return) really moves in an elliptical and not in a parabolic orbit.
Orbit
Bessel was able to determine an elliptical orbit for the comet from the observation data over a period of 187 days , which is inclined by around 63 ° to the ecliptic . At the point of the orbit closest to the sun ( perihelion ), which the comet traversed on September 19, 1807, it was located somewhat within the orbit of Venus at about 96.7 million km from the sun . Already on September 11th it had approached Venus within 116 million km and on September 15th Mars within 125 million km. On September 26th it passed the earth at a distance of 1.15 AU / 172.5 million km. This is an unusually long distance to Earth for a large comet, only two other large comets have come no closer than 1 AU, namely C / 1811 F1 and C / 1995 O1 (Hale-Bopp) .
The comet moves in an extremely elongated elliptical orbit around the sun. According to the orbital elements , which are afflicted with a certain uncertainty, it could have appeared in antiquity around the year 147. During the last passage through the inner solar system in 1807, its orbital eccentricity was reduced slightly by 0.0005 and its semi-major axis from around 140 AU to around 126 AU, so that its orbital period was significantly reduced. When it reaches the point of its orbit furthest from the sun ( aphelion ) around the year 2520 , it will be about 37.8 billion km away from the sun, over 252 times as far as the earth and almost 8½ times as far as Neptune . Its orbital speed in aphelion is only about 0.13 km / s. The comet's next perihelion passage may occur around the year 3230.
See also
Individual evidence
- ^ J. Russell Hind : The Comets: A Descriptive Treatise , 1852, p. 154 (English)
- ^ A b Greg Bryant: Bright Comets Of The Last Two Centuries - Part I. Retrieved June 26, 2014 (English).
- ^ JH Schroeter: Observations of the great Comet from 1807 . Goettingen 1811.
- ↑ GW Kronk: Cometography - A Catalog of Comets, Volume 2. 1800-1899 . Cambridge University Press, 2003, ISBN 0-521-58505-8 , pp. 10-14.
- ^ Donald K. Yeomans: NASA JPL Solar System Dynamics: Great Comets in History. Retrieved June 17, 2014 .
- ↑ FW Bessel: Investigations into the apparent and true orbit of the great comet that appeared in 1807 . Koenigsberg 1810.
- ↑ C / 1807 R1 (Great Comet) in the Small-Body Database of the Jet Propulsion Laboratory (English).
- ↑ SOLEX 11.0 A. Vitagliano. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .