Comet McNaught, also known as the Great Comet of 2007 and given the designation C/2006 P1, is a

non-periodic comet The following is a list of comets with a very high Orbital eccentricity, eccentricity (generally 0.99 or higher) and a Orbital period, period of over 1,000 years that do not quite have a high enough Escape velocity, velocity to escape the Solar Sys ...

discovered on 7 August 2006 by British-Australian astronomer

Robert H. McNaught Robert H. McNaught (born in Scotland in 1956) is a Scottish-Australian astronomer at the Research School of Astronomy and Astrophysics of the Australian National University (ANU). He has collaborated with David J. Asher of the Armagh Observator ...

using the

Uppsala Southern Schmidt Telescope The Uppsala Schmidt Telescope is a Schmidt telescope located in Australia. It was moved to Siding Spring Observatory from Mount Stromlo Observatory in 1982. The instrument has been used to study galaxies, asteroids and comets. It was last dedi ...

. It was the brightest comet in over 40 years, and was easily visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

for observers in the Southern Hemisphere in January and February 2007. With an estimated peak

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of −5.5, the comet was the second-brightest since 1935. Around

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

on 12 January, it was visible worldwide in broad daylight. Its tail measured an estimated at in length and stretched 35 degrees across the sky at its peak. The brightness of C/2006 P1 near perihelion was enhanced by

forward scatter Forward scattering is the deflection of waves by small angles so that they continue to move in close to the same direction as before the scattering. It can occur with all types of waves, for instance light, ultraviolet radiation, X-rays as well as ...

ing.

Discovery

McNaught discovered the comet in a

CCD CCD may refer to: Science and technology * Charge-coupled device, an electronic light sensor used in various devices including digital cameras * .ccd, the filename extension for CloneCD's CD image file * Carbonate compensation depth, a property ...

image on 7 August 2006 during the course of routine observations for the

Siding Spring Survey The Siding Spring Survey (SSS) was a near-Earth object search program that used the 0.5-metre Uppsala Southern Schmidt Telescope at Siding Spring Observatory, New South Wales, Australia. It was the southern hemisphere counterpart of the Catalin ...

, which searched for Near-Earth Objects that might represent a collision threat to Earth. The comet was discovered in

Ophiuchus Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constellati ...

, shining very dimly at a magnitude of about +17. From August through November 2006, the comet was imaged and tracked as it moved through Ophiuchus and Scorpius, brightening as high as apparent magnitude, magnitude +9, still too dim to be seen with the unaided eye. Then, for most of December, the comet was lost in the glare of the Sun. Upon recovery, it became apparent that the comet was brightening very fast, reaching naked-eye visibility in early January 2007. It was visible to northern hemisphere observers, in Sagittarius (constellation), Sagittarius and surrounding constellations, until about 13 January. Perihelion was 12 January at a distance of . This was close enough to the Sun to be observed by the space-based Solar and Heliospheric Observatory, Solar and Heliospheric Observatory (SOHO). The comet entered SOHO's Large Angle and Spectrometric Coronagraph, LASCO C3 camera's field of view on 12 January, and was viewable on the World Wide Web, web in near real-time. The comet left SOHO's field of view on 16 January. Due to its proximity to the Sun, the Northern Hemisphere ground-based viewers had a short window for viewing, and the comet could be spotted only during bright twilight. As it reached perihelion on 12 January, it became the brightest comet since Comet Ikeya–Seki in 1965. The comet was dubbed the ''Great Comet of 2007'' by Space.com. On 13 and 14 January 2007, the comet attained an estimated maximum apparent magnitude of −5.5. It was bright enough to be visible in daylight about 5°–10° southeast of the Sun from 12 to 14 January. The closest approach to the Earth occurred on 15 January 2007, at a distance of 0.82 AU. After passing the Sun, McNaught became visible in the Southern Hemisphere. In Australia, according to Siding Spring Observatory at Coonabarabran, where the comet was discovered, it was to have reached its theoretical peak in brightness on Sunday 14 January just after sunset, when it would have been visible for 23 minutes. On 15 January the comet was observed at Perth Observatory with an estimated apparent magnitude of −4.0.

Exploration

The Ulysses (spacecraft), ''Ulysses'' spacecraft made an unexpected pass through the tail of the comet on 3 February 2007. Evidence of the encounter was published in the 1 October 2007 issue of ''The Astrophysical Journal''. ''Ulysses'' flew through McNaught's ion tail from the comet's core and instrument readings showed that there was "complex chemistry" in the region. The Solar Wind Ion Composition Spectrometer (SWICS) aboard ''Ulysses'' measured Comet McNaught's tail composition and detected unexpected ions. It was the first time that O³⁺ oxygen ions were detected near a comet. This suggested that the solar wind ions, which did not originally have most of their electrons, gained some electrons while passing through the comet's atmosphere. SWICS also measured the speed of the solar wind, and found that even at 260 million kilometres (160 million miles) from the comet's nucleus, the tail had slowed the solar wind to half its normal speed. The solar wind should usually be about per second at that distance from the Sun, but inside the comet's ion tail, it was less than per second. Prof. George Gloeckler, the principal investigator on the Solar Wind Ion Composition Spectrometer (SWICS), said the discovery was important as the composition of comets told them about conditions approximately 4.5 billion years ago when the Solar System was formed.

Orbit

Comet C/2006 P1 took millions of years coming directly from the Oort cloud. It follows a hyperbolic trajectory (with an Osculating orbit, osculating eccentricity larger than 1) during its passage through the inner Solar System, but the eccentricity will drop below 1 after it leaves the influence of the planets and it will remain bound to the Solar System as an Oort cloud comet. Given the orbital eccentricity of this object, different Epoch (astronomy), epochs can generate quite different heliocentric unperturbed Two-body problem, two-body curve fitting, best-fit solutions to the aphelion distance (maximum distance) of this object. For objects at such high eccentricity, the Sun's Barycenter, barycentric coordinates are more stable than heliocentric coordinates. Using JPL Horizons On-Line Ephemeris System, JPL Horizons, the barycentric orbital elements for epoch 2050 generate a Semi-major and semi-minor axes, semi-major axis of 2050 AU and a period of approximately 92,700 years.

Gallery

Image:Comet McNaught.jpg, Over Iceland on 9 January Image:McNaughtComet.jpg, Just after sunset from Perth, Western Australia, Perth, Western Australia on 16 January Image:Cometperth3.jpg, Over Perth, Western Australia, Perth, Western Australia at 9 p.m. on 17 January File:Comet McNaught at South Beach.jpg, Seen from South Beach, Fremantle, Western Australia, Fremantle, Western Australia on 17 January. The lights at the bottom are navigation lights in Gage Roads. Image:Comet McNaught Windhoek 2007 Jan 17.jpg, Windhoek, Namibia on 17 January at 8 p.m. local time File:Comet McNaught (2).jpg, Setting behind the Andes, at San Carlos de Bariloche, Bariloche, Argentina, on 17 January Image:Cometmcnaughtchrisn1.jpg, 18 January from Pukekohe, New Zealand Image:Comet McNaught from La Perouse 3.JPG, 19 January from La Perouse, Sydney, Australia Image:Comet McNaught Signal Hill 20070119 1.jpg, From Signal Hill (Cape Town), Signal Hill, Cape Town on 19 January. The silhouette of Lion's Head (Cape Town), Lion's Head is visible on the left, while on the right Venus sets over the Atlantic Ocean. Image:sat comet WEB.jpg, 20 January from Lawlers, Western Australia Image:Villa Alemana Region of Valparaiso, Chile.jpg, Villa Alemana Region of Valparaiso, Chile on 20 January Image:2007 01 21 Comet McNaught Canberra Red Hill.jpg, from Red Hill, Australian Capital Territory, Red Hill, Canberra on 21 January Image:Mcnaught daylight20070113.jpg, Comet McNaught in broad daylight while it was visible by naked eye. Taken on 13 January at 14:00 UTC in Gais, Switzerland. Image:Comet tail.jpg, The tail of the comet Comet McNaught was still seen in the Northern hemisphere after the comet itself was long gone. The picture also shows the Moon and Venus. Image:Inferior mirage of sunset comet.jpg, A very rare sequence of the inferior Mirage of astronomical objects, Mirage of the comet set

Discovery

Exploration

Orbit

Gallery

See also

References

Notes

Citations

External links