Comet Hale–Bopp is a comet that was perhaps the most widely observed of the 20th century, and one of the brightest seen for many decades.
A near-Earth object (NEO) is any small Solar System body whose orbit brings it to proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). If a NEO's orbit crosses the Earth's and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but a small fraction are comets.
Comet Encke or Encke's Comet is a periodic comet that completes an orbit of the Sun once every 3.3 years. Encke was first recorded by Pierre Méchain in 1786, but it was not recognized as a periodic comet until 1819 when its orbit was computed by Johann Franz Encke; like Halley's Comet, it is unusual in being named after the calculator of its orbit rather than its discoverer. Like most comets, it has a very low albedo, reflecting only 4.6% of the light it receives. The diameter of the nucleus of Encke's Comet is 4.8 km.
Biela's Comet or Comet Biela was a periodic Jupiter-family comet first recorded in 1772 by Montaigne and Messier and finally identified as periodic in 1826 by Wilhelm von Biela. It was subsequently observed to split in two and has not been seen since 1852. As a result, it is currently considered to have been destroyed, although remnants appeared to have survived for some time as a meteor shower, the Andromedids.
The Comet Rendezvous Asteroid Flyby (CRAF) was a cancelled plan for a NASA led exploratory mission designed by the Jet Propulsion Laboratory during the mid-to-late 1980s and early 1990s, that planned to send a spacecraft to encounter an asteroid, and then to rendezvous with a comet and fly alongside it for nearly three years. The project was eventually canceled when it went over budget; most of the money still left was redirected to its twin spacecraft, Cassini–Huygens, destined for Saturn, so it could survive Congressional budget cutbacks. Most of CRAF's scientific objectives were later accomplished by the smaller NASA spacecraft Stardust and Deep Impact, and by ESA's flagship Rosetta mission.
The Halley Armada is the name of five space probes sent to examine Halley's Comet during its 1986 sojourn through the inner Solar System, connected with apparition "1P/1982 U1". The armada consisted of one probe from the European Space Agency, two probes that were joint projects between the Soviet Union and France and two probes from the Institute of Space and Astronautical Science of Japan.
The nucleus is the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun. A typical comet nucleus has an albedo of 0.04. This is blacker than coal, and may be caused by a covering of dust.
Stephen J. Edberg is a scientist at the Jet Propulsion Laboratory. He is perhaps best known for creating collaborative efforts between amateur and professional astronomers. A professional astronomer since 1970, Edberg still considers himself to be an active amateur astronomer as well and is an active astronomical observer, photographer, and telescope maker. He presently serves as staff astronomer for the Solar System Exploration website posted by NASA Headquarters and staff scientist for Earth science communication and for Exoplanet Exploration communication.
3537 Jürgen, provisional designation 1982 VT, is a stony Eunomia asteroid from the middle region of the asteroid belt, approximately 8 kilometers in diameter. It was discovered by American astronomer Edward Bowell at Lowell's Anderson Mesa Station, Arizona, on 15 November 1982. It was named after planetary scientist Jürgen Rahe.
The Great Southern Comet of 1887, or C/1887 B1 using its International Astronomical Union (IAU) designation, was a bright comet seen from the Southern Hemisphere during January 1887. Later calculations indicated it to be part of the Kreutz Sungrazing group.
The Great Comet of 1901, sometimes known as Comet Viscara, formally designated C/1901 G1, was a comet which became bright in the spring of 1901. Visible exclusively from the southern hemisphere, it was discovered on the morning of April 12, 1901 as a naked-eye object of second magnitude with a short tail. On the day of perihelion passage, the comet's head was reported as deep yellowish in color, trailing a 10-degree tail. It was last seen by the naked eye on May 23.
Comet Swift–Tuttle is a periodic comet with a current (osculating) orbital period of 133 years. It fits the classical definition of a Halley-type comet with a period between 20 and 200 years. It was independently discovered by Lewis Swift on July 16, 1862 and by Horace Parnell Tuttle on July 19, 1862. It has a well determined orbit and has a comet nucleus 26 km in diameter.
Comet ISON, formally known as C/2012 S1, was a sungrazing comet discovered on 21 September 2012 by Vitaly Nevsky and Artyom Novichonok. The discovery was made using the 0.4-meter (16 in) reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia. Data processing was carried out by automated asteroid-discovery program CoLiTec. Precovery images by the Mount Lemmon Survey from 28 December 2011 and by Pan-STARRS from 28 January 2012 were quickly located. Follow-up observations were made on 22 September by a team from Remanzacco Observatory in Italy using the iTelescope network. The discovery was announced by the Minor Planet Center on 24 September. Observations by Swift in January 2013 suggested that Comet ISON's nucleus was around 5 kilometers (3 mi) in diameter. Later estimates were that the nucleus was only about 2 kilometers (1 mi) in diameter. Mars Reconnaissance Orbiter (MRO) observations suggested the nucleus was smaller than 0.8 kilometers (0.5 mi) in diameter.
C/1807 R1 is a long-period comet, which in 1807 was visible to naked-eye observers in the northern hemisphere from early September to late December. On the basis of its outstanding brightness it is called a great comet.
C/1865 B1 was a non-periodic comet, which in 1865 was so bright that it was visible to unaided-eye observations in the Southern Hemisphere. The comet could not be seen from the Northern Hemisphere. {may have been generally true, but 1865 soldier's diary in Washington DC showed, March 5th "I saw a star at tenn or eleven O clock in the fornoon", and March 6th "saw a star in the middle of the day"}
P/2016 BA14 is a near-Earth object and periodic comet of the Jupiter family, that was radar imaged at distance of 2.2 million miles during a flyby of Earth in 2016. This enabled the size of the nucleus to be calculated to be about 3000 feet to 3300 ft in diameter. Four noted aspects to BA14 are that it was discovered as an asteroid first, it was much bigger than expected going from perhaps 125 meters to 1000 meters, it was the closest approach by a comet since 1770, and finally, it has a very similar orbit as numbered comet 252P/LINEAR, and may be related to it.
Chinese records of comets are the most extensive and accurate in existence from the ancient and medieval periods, and stretch back across three millennia. Records exist at least as far back as 613 BC, and records may have been kept for many centuries before this. There are continuous records all the way through to the nineteenth century, using substantially consistent methods throughout. Chinese data accuracy is unsurpassed in the ancient world and was not overtaken by Western accuracy until the fifteenth century or, in some respects, not until the twentieth century.
