Friday 3 January 2014

Comet McNaught (C/2006 P1)

Discovered by:        Robert H. McNaught
Discovery date:       August 7, 2006
Also known as:       The Great Comet of 2007
Peak magnitude:     -5.5


Aphelion:                 4100 AU (613 billion kilometres or 381 billion miles)
Perihelion:               0.17075 AU (25.54 million kilometres or 15.87 million miles)
Semi-major axis:      2050 AU (307 billion kilometres or 191 billion miles)
Eccentricity:            1.000019
Orbital period:          92,600 years
Inclination:               77.8 degrees

Last perihelion:         January 12, 2007
Next perihelion:        unknown


Comet P1 McNaught taken from Swifts Creek, Victoria, Australia on January 24, 2007
Comet McNaught is also known as the Great Comet of 2007

Discovered on August 7, 2006 by British-Australian astronomer Robert H. McNaught using the Uppsala Southern Schmidt Telescope as part of the Siding Spring Survey (Near-Earth Object search program).

Magnitude at discovery was a dim +17.

During January and February 2007 it was easily visible to the naked eye for Southern Hemisphere based observers.

Reached perihelion on January 12, 2007 when 0.17 AU (25.5 million kilometres or 15.9 million miles) from the Sun and visible in broad daylight.

Observed by the space-based Solar and Heliospheric Observatory (SOHO).

Comet sported a brilliant fan-shaped that measured 35 degrees.

It was the brightest comet since Ikeya-Seki in 1965. Peaked at magnitude -5.5 just after perihelion.

Perigee (closest approach to the Earth) was January 15, 2007, at a distance of 0.82 AU (122.7 million kilometres or 76.2 million miles).

On February 3, 2007 the Ulysses spacecraft made an unexpected pass through the comets ion tail. The probe was located 258 million kilometers (160 million miles) from the comets nucleus. Analysis of the resulting data showed a complex chemistry included the detection of O3+ oxygen ions near to a comet for the first time.

During its passage through the Solar System, McNaught followed a hyperbolic trajectory (eccentricity greater than 1). Normally with such an orbit the comet would leave the Solar System and never return, but due to gravitational influence of the planets the eccentricity is now believed to be below 1 and McNaught will eventually return.

Estimated to return in approx. 92,600 years time.


Comet West (C/1975 V1)

Discovered by:        Richard M. West
Discovery date:       August 10, 1975
Peak magnitude:    -3.0


Aphelion:                 70,000 AU (10,470 billion kms or 6,500 billion miles or 1.1 light-years)
Perihelion:               0.197 AU (29.47 million kilometres or 18.31 million miles)
Semi-major axis:      35,000 AU (5,235 billion kilometres or 3,250 billion miles)
Eccentricity:            0.99997
Orbital period:          unknown maybe as large as 6 million years
Inclination:               43.1 degrees

Last perihelion:        February 25, 1976
Next perihelion:       unknown

Comet West photographed in March 1976 (J. Linder/ESO)

Discovered photographically on August 10, 1975 by Richard M. West of the European Southern Observatory.

At the time, Comet West was at magnitude 14, had a small dust tail and was located 2.98 AU from the Sun (beyond the orbit of Mars).

Passed perihelion on February 25, 1976.

The comet nucleus was observed to split into four fragments as it passed by the Sun. At the time this was one of very few comet breakups observed, the most notable previous example being the Great Comet of 1882. More recently, comets Schwassmann-Wachmann-3 (73/P), C/1999 S4 LINEAR, 57/P du Toit-Neujmin-Delporte and ISON (C/2012 S1) have all been observed to disintegrate during their passage close to the Sun.

Peak magnitude was -3 and bright enough to be visible during daylight for a couple of days. This was much brighter than originally predicted with Comet West exceeding expectations.

Although a spectacular object before sunrise in March 1976, Comet West received very little media coverage. This was partly due to the display of Comet Kohoutek (C/1973 E1) in 1973, which had been widely predicted to be the "comet of the century" but in the end fell well short and was very disappointing. As a result scientists were wary of making predictions, in particular those of a spectacular nature.

At peak the comet displayed a sensational curved fanned tail tens of degrees in length. Comet McNaught (C/2006 P1) in 2007 was similar in appearance. 

With a near parabolic orbit, the orbital period is very difficult to accurately calculate. Estimates range from 250,000 years to 6 million years.