International Comet Quarterly

Press Release/Article on Comet C/2006 P1 (McNaught)

PRESS RELEASE from THE INTERNATIONAL COMET QUARTERLY
****************************************************

BRIGHTEST COMET IN OVER FORTY YEARS VISIBLE IN DAYLIGHT

by Daniel W. E. Green

CAMBRIDGE (Massachusetts), 2007 Jan. 13 -- The brightest comet to be viewed from the earth since 1965 is currently rounding the sun, and should put on a splendid display for southern-hemisphere observers in the second half of January. Astronomers have been pleasantly surprised by the amount of rapid brightening in the first two weeks of January of this comet, which was first found last August.

Formally known as comet C/2006 P1 (McNaught), it was discovered on 2006 August 7 by Scottish-Australian astronomer Robert H. McNaught as a faint fuzzy object on images obtained with an electronic camera as part of the Siding Spring Survey for near-earth objects in Australia. It is important to refer to the comet as "2006 P1" because McNaught has discovered 31 other comets over the past three decades (so "comet McNaught" is not a name unique to this particular comet).

McNaught's bright comet is only a few degrees from the sun now, but because of its recent brightness surge, it was visible low in the western sky for some minutes just after sunset in bright evening twilight during the past week. Many experienced observers have been following the comet during the last few days in broad daylight with telescopes, binoculars, and even the unaided eye as it has surpassed the bright planet Venus in brightness -- though it is certainly not an easy object only a few degrees from the sun. Unfortunately, for the comet's show for the second and third weeks of January, it will be invisible for northern-hemisphere observers when the sun is below the horizon.

Comet 2006 P1 should be visible as a splendid object for observers south of the equator beginning this next week right after sunset. Observers should have a clear sky and unobstructed western horizon. A pair of binoculars may be helpful to find the comet first, and binoculars will show more details than the naked eye can. The best visibility will be the third week of January for southern-hemisphere observers, but the comet should still be a nice sight during the fourth week in January as it moves away from the sun and earth, causing it to fade in brightness and the tail to shrink.

Comets are known for often being notoriously unpredictable when it comes to their brightness: some comets predicted to be bright have not panned out and thus disappointed the general public, while others have sudden outbursts and become unexpectedly bright (sometimes due to splitting or breaking up of the cometary nucleus). For this reason, astronomers are often reluctant to get the news media and the general public excited about a possibly bright comet before it becomes bright.

While comets are usually known for their tails, it is their coma (or head) that normally contains the bulk of the comet's brightness, as that is where most of the material resides that reflects sunlight or fluoresces; tail material is much less dense. At its core, a comet has a small nucleus usually only a mile or two across and made of rock and ices, and thus is really a type of minor planet. The size of the planetary nucleus of comet 2006 P1 is uncertain because telescopes cannot view the nucleus directly due to the dense surrounding atmosphere.

As observed with the new NASA spacecraft STEREO-B on Thursday, McNaught's comet 2006 P1 already has a beautiful, structured dust tail that stretches more than million miles away from the comet's head in space. When a comet approaches the inner solar system, the sun's heating causes its ices to sublimate (or "evaporate" directly from an ice to a gas), carrying dust and bits of rock into space in jets of gas. This in turn forms the comet's coma (or atmosphere) and pushes the coma's gas and dust particles anti-sunward into the comet's visible tail.

People often mistake comets for meteors, but comets are planetary bodies that orbit the sun, whereas meteors are only small bits of debris scooped up by the earth in its orbit about the sun. Comets rise and set like the sun, moon, and stars, but meteors (or "shooting stars") streak across the sky in a few seconds or less as they burn up high in the earth's atmosphere. Meteor showers occur at regular times each year when the earth passes through streams of debris left behind by comets as they orbit the sun.

The above article may be linked to or printed in its entirety in any newspaper or magazine article provided that the author's name is included and/or reference is made to the International Comet Quarterly. The International Comet Quarterly is a printed journal devoted to the observation of and news concerning comets with an extensive webpage containing useful information about comets. Contact its editor, Dr. Daniel W. E. Green, at icq@cfa.harvard.edu, with further questions. Green directs the Central Bureau for Astronomical Telegrams at the Harvard-Smithsonian Center for Astrophysics on behalf of the International Astronomical Union; the CBAT announces discoveries, designations, and names of new comets.

This article is also available in plain ASCII text.