Comet McNaught viewed over the Pacific in 2007. Credit: Sebastian Deiries/ESO.

Does McNaught Take Title for Biggest Comet Ever?

Article Updated: 24 Dec , 2015
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There are different ways to measure a comet. The Hale Bopp Comet, for example has a nucleus of more than 60 miles in diameter, which is thought to be the biggest ever encountered, so far. And Comet Hyakutake’s tail stretched out at a distance of more than 500 million km from the nucleus, the largest known. But now a group of scientists have identified a new category of measuring a comet’s size: the region of space disturbed by the comet’s presence. And for this class, first prize goes to Comet C/2006 P1 McNaught, which graced our skies in Janauary and February 2007. Of course, McNaught might win the prize for most picturesque comet, too, as this stunning image from Sebastian Deiries of ESO shows.

Dr. Geraint Jones of University College, London and his team used 2007 data from the now-inoperable Ulysses spacecraft, which was able to gauge the size of the region of space disturbed by the comet’s presence.

Ulysses encountered McNaught’s tail of ionized gas at a distance downstream of the comet’s nucleus more than 225 million kilometers. This is far beyond the spectacular dust tail that was visible from Earth in 2007.

“It was very difficult to observe Comet McNaught’s plasma tail remotely in comparison with the bright dust tail,” said Jones, “so we can’t really estimate how long it might be. What we can say is that Ulysses took just 2.5 days to traverse the shocked solar wind surrounding Comet Hyakutake, compared to an incredible 18 days in shocked wind surrounding Comet McNaught. This shows that the comet was not only spectacular from the ground; it was a truly immense obstacle to the solar wind.”

A comparison with crossing times for other comet encounters demonstrates the huge scale of Comet McNaught. The Giotto spacecraft’s encounter with Comet Grigg-Skjellerup in 1992 took less than an hour from one shock crossing to another; to cross the shocked region at Comet Halley took a few hours.

“The scale of an active comet depends on the level of outgassing rather than the size of the nucleus,” said Jones. “Comet nuclei aren’t necessarily active over their entire surfaces; what we can say is that McNaught’s level of gas production was clearly much higher than that of Hyakutake.”

Jones presented his findings at the RAS National Astronomy Meeting in Glasgow, Scotland.

Source: RAS NAM

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4 Responses

  1. Hon. Salacious B. Crumb says:

    No, but is sure up there.

    I talked to Rob McNaught at the National Australian Convention Of Amateur Astronomers (NACAA) in Penrith, Ne South Wales in Easter 2008. I asked him “How does it feel to be immortal?” Slightly perplexed, and I explained that in the centuries to come his name would spoken – just like all the other famous and remembered bright comets – an that his name would go on well after he was gone. He replied, “I never thought of it that way.”

    IMO this is what makes this comet so great and it the real answer to the question posed in this UT story. Biggest comet of all time is a big call, because so few have been seen in recent memory and that throughout history there has been many comets observed which might have taken the title. At its closest it lay just 0.1326 AU from Earth or about 19 million kilometres (12 million miles)
    The main contenders could be Comet Tebbutt 1861 II (C/1861 J1), which in June 1861, the main tail now stretched up to 120º in length and 6º wide! Amazingly, on the 30th June , the daytime sky adopted a peculiar yellow hue, though some in Sydney, including Tebbutt, reported this as more whitish, and some later compared it to the similar soft glow of aurorae. Worldwide, this produced various phenomena, and a few even reported of an apparent observable dimming of sunlight – to the extent that candles were required to indoors.
    A drawn image show the size at one time is extraordinary C/1861 J1 (Great Comet of 1861)

    Now that a real comet!

    Note: There is a fabulous book entitled “The Greatest Comets in History” (2009) by Davis Seargent published by Springer Publish. Probably the best one on this topic. (I have no association with this publication, and suggest it as mere comment) [The 1861 comet appears on page 136-142 in a 200-odd page book!]

  2. Hon. Salacious B. Crumb says:

    Oops! Too many errors here! (What was I thinking!) Here it is again. (Nancy delete the first one please – if only there was an text editor in UT!]

    No, but is sure up there.
    I talked to Rob McNaught at the National Australian Convention of Amateur Astronomers (NACAA) in Penrith, New South Wales in Easter 2008. I asked him “How does it feel to be immortal?” Slightly perplexed, and I explained that in the centuries to come his name would spoken – just like all the other famous and remembered bright comets – and that his name would go on well after he was gone. He replied, “I never thought of it that way.”

    IMO this is what makes this comet so great and it the real answer to the question posed in this UT story. Biggest comet of all time is a big call, because so few have been seen in recent memory. Throughout history there has been many comets observed which might have also taken the title.

    The main contenders could be Comet Tebbutt 1861 II (C/1861 J1), which in June 1861, found the main tail stretching up to 120º in length and 6º wide! Amazingly, on 30th June 1861, the daytime sky adopted a peculiar yellow hue, as the comet passed btween the Earth and the Sun. Some visual observers in Sydney, including Tebbutt, reported this as more whitish, and some later compared it to the similar soft glow of aurorae. Worldwide, this was said to produce various phenomena, and a few even reported of an apparent observable dimming of sunlight – to the extent that candles were required to indoors. At its closest it lay just 0.1326 AU from Earth or about 19 million kilometres (12 million miles)

    A drawn picture shows the apparent size at one time is extraordinary. C/1861 J1 (Great Comet of 1861) stretched from Ursa Major to Cassiopeia – centred roughly on Polaris, while the nucleus of the comet was on the horizon along with the 1st magnitude star Capella / Alpha Aurigae!

    Now that a real comet!

    Note: There is a fabulous book entitled The Greatest Comets in History (2009) by David Seargent published by Springer Publish. This is probably one of the the best on this topic. (I have no association with this publication, and suggest it as mere comment) [The 1861 comet appears on page 136-142 in a 200-odd page book!]

  3. Aqua says:

    My viewing of C. McNaught was limited to two evenings when it appeared very low on the horizon as it plunged South…. I DID get a couple images, but wish I could have traveled south to have seen it in all its glory!

    Recently, 3 Kreutz Sungrazer comets plunged into Sol… The three went undetected until just before they made their fiery exit(s). It is quite possible that a Sungrazer making an approach which misses Sol, might go totally undetected on Earth until too late…

    These occurrences made me wonder after the pieces which broke off periodic Comet P73/Schwassman-Wachmann 3. Where are those pieces now?

  4. Aodhhan says:

    My favorite bumper sticker… from the Hale-Bopp time frame, “So many idiots, not enough comets”.

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