In astronomy, absolute magnitude is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly 10 parsecs, without extinction of its light due to absorption by interstellar matter and cosmic dust. By hypothetically placing all objects at a standard reference distance from the observer, their luminosities can be directly compared among each other on a magnitude scale. For Solar System bodies that shine in reflected light, a different definition of absolute magnitude (H) is used, based on a standard reference distance of one astronomical unit.
The Geminids are a prolific meteor shower caused by the object 3200 Phaethon, which is thought to be a Palladian asteroid with a "rock comet" orbit. This would make the Geminids, together with the Quadrantids, the only major meteor showers not originating from a comet. The meteors from this shower are slow moving, can be seen in December and usually peak around December 4–16, with the date of highest intensity being the morning of December 14. Recent showers have seen 120–160 meteors per hour under optimal conditions, generally around 02:00 to 03:00 local time. Geminids were first observed in 1862, much more recently than other showers such as the Perseids and Leonids.
A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so almost all of them disintegrate and never hit the Earth's surface. Very intense or unusual meteor showers are known as meteor outbursts and meteor storms, which produce at least 1,000 meteors an hour, most notably from the Leonids. The Meteor Data Centre lists over 900 suspected meteor showers of which about 100 are well established. Several organizations point to viewing opportunities on the Internet. NASA maintains a daily map of active meteor showers.
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 on 17 January 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 its 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 its nucleus receives, although comets generate a large coma and tail that can make them much more visible during their perihelion. The diameter of the nucleus of Encke's Comet is 4.8 km.
Lewis A. Swift was an American astronomer who discovered 13 comets and 1,248 previously uncatalogued nebulae. Only William Herschel discovered more nebulae visually.
3200 Phaethon, provisionally designated 1983 TB, is an active Apollo asteroid with an orbit that brings it closer to the Sun than any other named asteroid. For this reason, it was named after the Greek myth of Phaëthon, son of the sun god Helios. It is 5.8 km (3.6 mi) in diameter and is the parent body of the Geminids meteor shower of mid-December. With an observation arc of 35+ years, it has a very well determined orbit. The 2017 Earth approach distance of about 10 million km was known with an accuracy of ±700 m.
Dia, also known as Jupiter LIII, is a prograde irregular satellite of Jupiter. Provisionally known as S/2000 J 11, it received its name on March 7, 2015. It is named after Dia, daughter of Deioneus, wife of Ixion. According to Homer, she was seduced by Zeus in stallion form; Pirithous was the issue.
Francesco Manca is an Italian amateur astronomer and discoverer of minor planets at the Sormano Astronomical Observatory in northern Italy.
The Astronomical Observatory of Modra, also known as Modra Observatory or the Astronomical and Geophysical observatory in Modra, is an astronomical observatory located in Modra, Slovakia. It is owned and operated by the Comenius University in Bratislava. The scientific research at the observatory is led by the Department of Astronomy, Physics of the Earth and Meteorology, Faculty of Mathematics, Physics and Informatics.
The Phoenicids are a minor meteor shower, first noticed by observers in New Zealand, Australia, the Indian Ocean, and South Africa during an outburst of approximately 100 meteors an hour that occurred during December 1956. Like other meteor showers, the Phoenicids get their name from the location of their radiant, which is in the constellation Phoenix. They are active from 29 November to 9 December, with a peak occurring around 5/6 December each year, and are best seen from the Southern Hemisphere.
Active asteroids are small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a coma, tail, or other visual evidence of mass-loss, but their orbits remain within Jupiter's orbit. These bodies were originally designated main-belt comets (MBCs) in 2006 by astronomers David Jewitt and Henry Hsieh, but this name implies they are necessarily icy in composition like a comet and that they only exist within the main-belt, whereas the growing population of active asteroids shows that this is not always the case.
354P/LINEAR, provisionally designated P/2010 A2 (LINEAR), is a small main-belt asteroid that was impacted by another asteroid sometime before 2010. It was discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) at Socorro, New Mexico on 6 January 2010. The asteroid possesses a dusty, comet-like trail of debris that remained for nearly a decade since impact. This was the first time a small-body collision had been observed; since then, minor planet 596 Scheila has also been seen to undergo a collision, in late 2010. The tail is created by millimeter-sized particles being pushed back by solar radiation pressure.
An Earth-grazing fireball is a fireball, a very bright meteor that enters Earth’s atmosphere and leaves again. Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in mid-air. These phenomena are then called Earth-grazing meteor processions and bolides. Famous examples of Earth-grazers are the 1972 Great Daylight Fireball and the Meteor Procession of July 20, 1860.
(196256) 2003 EH1 is an asteroid, classified as near-Earth object of the Amor group. It was discovered on 6 March 2003, by astronomers of the LONEOS program at Anderson Mesa Station near Flagstaff, Arizona, in the United States. Peter Jenniskens (2003–2004) proposed that it is the parent body of the Quadrantid meteor shower. 2003 EH1 is likely an extinct comet and may even be related to the comet C/1490 Y1. 2003 EH1 came to perihelion on 12 March 2014.
209P/LINEAR is a periodic comet with an orbital period of 5.1 years. The comet has extremely low activity for its size and is probably in the process of evolving into an extinct comet.
Comet 252P/LINEAR is a periodic comet and near-Earth object discovered by the LINEAR survey on April 7, 2000. The comet is a Jupiter family comet, meaning that it passes quite close to the orbit of Jupiter.
2019 OK is a near-Earth asteroid noted for its sudden, surprise discovery on the day before its close flyby in 2019. The object's size is estimated at 57 to 130 metres across, the closest asteroid of such size discovered in 2019. It is uncommon for asteroids of this moderately large size to pass within 100,000 km (62,000 mi) of Earth.
CAMS is a NASA-sponsored international project that tracks and triangulates meteors during night-time video surveillance in order to map and monitor meteor showers. Data processing is housed at the Carl Sagan Center of the SETI Institute in California, USA. Goal of CAMS is to validate the International Astronomical Union's Working List of Meteor Showers, discover new meteor showers, and predict future meteor showers.
(155140) 2005 UD is an asteroid on an eccentric orbit, classified as a near-Earth object of the Apollo group. It was discovered on 22 October 2005, by the Catalina Sky Survey at the Catalina Station in Arizona, United States. 2005 UD is thought to be a possible fragment of 3200 Phaethon due to its similar orbit, although it is not dynamically associated with the Geminid meteor stream produced by Phaethon.
P/2016 J1 (PanSTARRS) is a pair of active main-belt asteroids that split apart from each other in early 2010. The brightest and largest component of the pair, P/2016 J1-A, was discovered first by the Pan-STARRS 1 survey at Haleakalā Observatory on 5 May 2016. Follow-up observations by the Canada-France-Hawaii Telescope at Mauna Kea Observatory discovered the second component, P/2016 J1-B, on 6 May 2016. Both asteroids are smaller than 1 kilometre (0.62 mi) in diameter, with P/2016 J1-A being roughly 0.6 km (0.37 mi) in diameter and P/2016 J1-B being roughly 0.3 km (0.19 mi) in diameter. The two components recurrently exhibit cometary activity as they approach the Sun near perihelion, suggesting that their activity is driven by sublimation of volatile compounds such as water.
