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Astronomical Observatory: Cool Images

Comet Pojmanski , Zach Smith

C/2006 A1, otherwise known as comet Pojmanski (after its discoverer), was officially discovered on January 1, 2006. At that time, it was about 113 million miles from earth and had a magnitude of 11 or 12. Its closest approach (perihelion) of the Sun was at 51.6 million miles. However, its closest approach to the earth was 71.7 million miles that occurred on March 5, 2006. It was predicted to reach a maximum magnitude of +6.5, but continued to surprise astronomers by increasing in magnitude until it reached near magnitude 5.

By applying a gamma function, we more clearly see the structure of the comet (above). The bright circular point in the center of the comet is the nucleus. This is composed of frozen gases with other solid particles interspersed. When the comet approaches the sun, the outer regions of the nucleus change to the gaseous phase, forming an envelope around the nucleus called the coma. Finally, there is the most familiar feature of comets: the tail. This is formed as solar winds propel gas and particles from the nucleus to for long streams on the opposite side of the comet.

The above image has a rotational gradient filter applied to it, which means that the image is rotated slightly than subtracted from the original image, in order to highlight its structure. The very light and very dark streaks represent the tail of the comet. Notice how the tail is not a single stream, but rather several different streams all emanating from the nucleus.

This movie shows the motion of the comet against the background of the stars. Note how the direction of the tail is not what you'd expect; intuition tells us that the tail should be pointed opposite the direction of motion, but in this case it is nearly perpendicular. This is because the tail of a comet always points away from the sun, regardless of the direction of its motion.

Right Ascension (J2000) approx. 20:35:13.70 at observation
Declination (J2000) approx. +03 04' 24.00" at observation
Dates observed

March 3, 2006

Filter used Clear
Exposure time

Still: 9x30s
Movie: 16 consecutive exposures, 10s each, 7:32-7:44AM EST


"See it Now: New Comet Brightens Rapidly", Joe Rao. 24 February 2006

"New comet visible", Kathy Hoogeboom, Calvin College Chimes March 3, 2006

Content updated 2006March09


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