☄ McNaught C/2006 P1

How to follow comet McNaught live

The panel above recomputes the position of McNaught every second in your browser: its distance from the Sun and from Earth, its position in the sky (right ascension and declination). It runs on the same kind of engine observatories use, a Kepler solver applied to the JPL osculating orbital elements, so the numbers are not a static snapshot, they keep ticking.

Just below, the top-down map of the Solar System shows exactly where McNaught is right now among the planets. You can fast-forward time with the day slider, zoom and pan, compare its distance to another body with a click, and press "Next event" to jump straight to perihelion. It is the most direct way to grasp the orbit of McNaught with no math at all.

Comet fact sheet

About McNaught

C/2006 P1, dubbed the Great Comet of 2007, is the brightest comet observed from Earth since Ikeya-Seki in 1965. At peak brightness on 12 January 2007, it reached apparent magnitude -5.5 during perihelion at just 0.17 astronomical units from the Sun, well inside Mercury's orbit. At that moment the comet was visible to the naked eye in full daylight for those who knew where to look.

In the days that followed, the comet swept rapidly into the southern celestial hemisphere and revealed a fan-shaped dust tail with fine striations known as synchrones, stretching up to 35 apparent degrees. Photographed extensively from Australia, South Africa and Patagonia, that tail made C/2006 P1 one of the most documented comets of the digital age.

History and discovery

Robert McNaught, a Scottish-Australian astronomer working at Siding Spring Observatory in Australia, detected the comet on 7 August 2006 using images from the 0.5-metre Uppsala Southern Schmidt telescope as part of the Catalina Sky Survey programme. McNaught is one of the world's most prolific discoverers of comets and asteroids, with more than 80 comets bearing his name over the course of his career.

At discovery, C/2006 P1 was just a faint magnitude-17 dot, nothing unusual. The quickly calculated orbit, however, revealed that perihelion would be extremely close to the Sun at just 0.17 AU, and that the object had potential to become exceptionally bright. Brightness predictions were followed with caution by the astronomical community, still sceptical after the disappointment of Comet Kohoutek in 1973 and the relatively modest showing of Halley in 1986.

In December 2006, as the comet began approaching the solar neighbourhood and brightening rapidly, it became clear that even the most optimistic forecasts would be exceeded. By 9 January 2007, at around magnitude -1, it was already visible in daylight to experienced observers.

Orbit and nature

C/2006 P1 has a parabolic orbit (eccentricity = 1.000019), indicating it is a dynamically new visitor from the Oort Cloud that had never previously passed through the inner Solar System. Perihelion occurred on 12 January 2007 at 0.17 AU from the Sun, well inside Mercury's orbit.

The extreme solar proximity explains the exceptional brightness: the nuclear surface heated to over 800 degrees Celsius evaporated volatile material in enormous quantities, feeding a giant coma and a record-length dust tail. The nucleus survived perihelion, though it lost considerable mass. Afterwards the comet moved rapidly south and became inaccessible to most northern-hemisphere observers.

Nucleus, coma and tail

The nucleus of C/2006 P1 was never photographed directly with sufficient resolution for a definitive measurement, as the dense gas-and-dust coma prevented resolution. Indirect estimates based on water production rates and luminosity point to a nucleus at least 15 to 25 km across, possibly larger, placing it among the largest well-observed comets of the modern era.

The coma expanded to the point where solar radiation pressure structured the dust tail into distinct fine bands, the synchrones. Each synchrone corresponds to particles ejected at the same moment and then separated by radiation pressure according to their size. A detailed analysis published in Icarus in 2019 temporally mapped McNaught's synchrones and identified a significant morphological change on 13-14 January 2007, attributed to Lorentz forces as the tail crossed the heliospheric current sheet.

The ion (plasma) tail was less visually prominent than the dust tail but equally rich scientifically. Spectra taken by the solar telescope THEMIS detected unusually abundant neutral sodium emission, published in Astronomy & Astrophysics in 2008.

The spectacle in the sky

At perihelion on 12 January 2007, the comet was so close to the Sun that observers had to block the solar disk to see it in daylight. Those with proper technique reported a whitish tail against the blue daytime sky. The LASCO instrument on the SOHO satellite recorded the comet crossing its field of view and revealed the internal tail structure in detail impossible to obtain from the ground.

In the days following perihelion, the comet swept rapidly south and became a spectacular evening object in the southern hemisphere through January and February 2007. The fan-shaped dust tail, extensively photographed from Australia and Patagonia, stretched up to 35 apparent degrees across the sky, equivalent to 70 full-Moon diameters placed side by side.

The best viewing windows fell between 13 and 25 January 2007 in the southern-hemisphere twilight sky. After that period, the comet receded and faded, becoming a binocular object and later a telescopic one through mid-March.

Science and observations

McNaught was observed by a wide network of professional telescopes and space instruments. In addition to SOHO-LASCO, NASA's STEREO-A and STEREO-B satellites, launched in 2006 to study the Sun in stereoscopy, recorded the comet and provided unprecedented angles of the tail. In 2010, an analysis published in Space Science Letters revealed that the comet's magnetosphere was more extensive than the Sun: the ion tail sheath was estimated to reach 1.5 AU in length, making C/2006 P1 the largest object ever measured in the Solar System in terms of plasma structure extent.

Molecular studies of the coma, published in 2011 in the Astrophysical Journal, detected OH, CN, C2, NH and other species typical of long-period comets, with volatiles relatively rich in carbon. Comparison with other very bright comets (Hale-Bopp, NEAT) showed that McNaught had a composition typical of an Oort Cloud comet uncontaminated by a previous inner Solar System passage, reinforcing its classification as a dynamically new object.

Key facts

• At magnitude -5.5, McNaught was the brightest comet since the Great Comet Ikeya-Seki of October 1965, which reached an estimated magnitude between -10 and -12.
• The dust tail measured approximately 74.9 million km in physical length (0.501 AU), making it one of the longest ever measured for a comet.
• A 2026 analysis using archival imagery found the nucleus rotation period before perihelion to be approximately 18.6 hours, deduced from periodic variations in ejected material jets.
• The comet has a parabolic orbit and will not return: it is leaving the Solar System permanently, unless some gravitational perturbation changes its course over centuries of interstellar travel.
• Despite being spectacular in the south, the comet was poorly seen in the north for geometric reasons: during perihelion it was too close to the horizon at dusk for most European and North American observers.
• Robert McNaught, its discoverer, has been observing comets since the 1980s through the Catalina Sky Survey and has more than 80 catalogued comets bearing his name, a record among contemporary professional astronomers.

Other comets

See the full comet catalogue.