Comet Swift–Tuttle
Encyclopedia
Comet Swift–Tuttle is a comet
that 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.
The comet
made a return appearance in 1992, when it was rediscovered by Japanese astronomer
Tsuruhiko Kiuchi and became visible with binoculars. Its solid nucleus
is about 27 kilometres (16.8 mi) across, considerably larger than the 10 km object hypothesized to have wiped out the dinosaurs in the Cretaceous–Paleogene extinction event.
It is the parent body of the Perseid
meteor shower
, perhaps the best known shower and among the most reliable in performance.
An unusual aspect of its orbit is that it is presently captured into a 1:11 orbital resonance
with Jupiter
; it completes one orbit for every 11 of Jupiter.
The ephemeris is available from NASA's Jet Propulsion Laboratory http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=109p, although it is not listed in NASA Close Approach Tables http://neo.jpl.nasa.gov/ca/ of Near Earth Objects
which puts it close to the Earth
and the Moon
. Upon its 1992 rediscovery, the comet's date of perihelion passage was off from the then-current prediction by 17 days. It was then noticed that, if its next perihelion passage (August 14, 2126) was also off by another 15 days, the comet would very likely strike the Earth or Moon. Given the size of the nucleus of Swift–Tuttle, this was of some concern. This prompted amateur astronomer and writer Gary W. Kronk
to search for previous apparitions of this comet. He found the comet was most likely observed by the Chinese in 69 BC
and AD 188
, which was quickly confirmed by Brian G. Marsden
. This information and subsequent observations have led to recalculation of its orbit, which indicates the comet's orbit is very stable, and that there is absolutely no threat over the next two thousand years. Astronomers believe that in the 2126 pass it will likely be a great naked-eye comet like Hale–Bopp.
A close encounter with Earth is predicted for the comet's return to the inner solar system in the year 4479, around Sept. 15; the closest approach is estimated to be 0.03–0.05 AU
, with a probability of impact of 1. Subsequent to 4479, the orbital evolution of the comet is more difficult to predict; the probability of Earth impact per orbit is estimated as 2. As the largest Solar System
object that makes repeated close passes of Earth, and which does so at a relative velocity of 60 km/s, leading to an estimated impact energy of ≈27 times that of the K–T impactor, Comet Swift–Tuttle has been described as "the single most dangerous object known to humanity".
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
that was independently discovered by Lewis Swift on July 16, 1862 and by Horace Parnell Tuttle
Horace Parnell Tuttle
Horace Parnell Tuttle was an American astronomer, a Civil War veteran and brother of astronomer Charles Wesley Tuttle ....
on July 19, 1862. It has a well determined orbit and has a comet nucleus
Comet nucleus
The nucleus is the solid, central part of a comet, popularly termed a dirty snowball. 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...
26 km in diameter.
The comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
made a return appearance in 1992, when it was rediscovered by Japanese astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
Tsuruhiko Kiuchi and became visible with binoculars. Its solid nucleus
Comet nucleus
The nucleus is the solid, central part of a comet, popularly termed a dirty snowball. 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...
is about 27 kilometres (16.8 mi) across, considerably larger than the 10 km object hypothesized to have wiped out the dinosaurs in the Cretaceous–Paleogene extinction event.
It is the parent body of the Perseid
Perseids
The Perseids are a prolific meteor shower associated with the comet Swift-Tuttle. The Perseids are so-called because the point from which they appear to come, called the radiant, lies in the constellation Perseus. The name derives in part from the word Perseides , a term found in Greek mythology...
meteor shower
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate 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...
, perhaps the best known shower and among the most reliable in performance.
An unusual aspect of its orbit is that it is presently captured into a 1:11 orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
with Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
; it completes one orbit for every 11 of Jupiter.
The ephemeris is available from NASA's Jet Propulsion Laboratory http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=109p, although it is not listed in NASA Close Approach Tables http://neo.jpl.nasa.gov/ca/ of Near Earth Objects
Potential threat to Earth
The comet is on an orbitOrbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
which puts it close to the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. Upon its 1992 rediscovery, the comet's date of perihelion passage was off from the then-current prediction by 17 days. It was then noticed that, if its next perihelion passage (August 14, 2126) was also off by another 15 days, the comet would very likely strike the Earth or Moon. Given the size of the nucleus of Swift–Tuttle, this was of some concern. This prompted amateur astronomer and writer Gary W. Kronk
Gary W. Kronk
Gary W. Kronk is an American amateur astronomer and writer.-Biography:Kronk was born in Granite City, Illinois, United States, on March 23, 1956...
to search for previous apparitions of this comet. He found the comet was most likely observed by the Chinese in 69 BC
69 BC
Year 69 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Hortalus and Metellus...
and AD 188
188
Year 188 was a leap year starting on Monday of the Julian calendar. At the time, it was known as the Year of the Consulship of Fuscianus and Silanus...
, which was quickly confirmed by Brian G. Marsden
Brian G. Marsden
Brian Geoffrey Marsden was a British astronomer born in Cambridge, England, and educated at The Perse School in Cambridge, New College, Oxford and Yale University. Dr...
. This information and subsequent observations have led to recalculation of its orbit, which indicates the comet's orbit is very stable, and that there is absolutely no threat over the next two thousand years. Astronomers believe that in the 2126 pass it will likely be a great naked-eye comet like Hale–Bopp.
A close encounter with Earth is predicted for the comet's return to the inner solar system in the year 4479, around Sept. 15; the closest approach is estimated to be 0.03–0.05 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, with a probability of impact of 1. Subsequent to 4479, the orbital evolution of the comet is more difficult to predict; the probability of Earth impact per orbit is estimated as 2. As the largest Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
object that makes repeated close passes of Earth, and which does so at a relative velocity of 60 km/s, leading to an estimated impact energy of ≈27 times that of the K–T impactor, Comet Swift–Tuttle has been described as "the single most dangerous object known to humanity".
External links
- 109P/Swift-Tuttle at the Minor Planet CenterMinor Planet CenterThe Minor Planet Center operates at the Smithsonian Astrophysical Observatory , which is part of the Center for Astrophysics along with the Harvard College Observatory ....
's Database - 109P/Swift–Tuttle at NASANASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Jet Propulsion LaboratoryJet Propulsion LaboratoryJet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
's Small-Body Database - Periodic Comet Swift–Tuttle from NASA's Astronomy Picture of the DayAstronomy Picture of the DayAstronomy Picture of the Day is a website provided by NASA and Michigan Technological University . According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."The photograph is not necessarily...