COMETS

Comets are small, fragile, irregularly shaped bodies composed of a mixture of
non-volatile grains  and frozen gases. They have highly elliptical orbits that bring them
very close to the Sun and swing them deeply into space, often beyond the orbit of
Pluto.  Comet structures are diverse and very dynamic, but they all develop a
surrounding cloud of diffuse material, called a coma, that usually grows in size and
brightness as the comet approaches the Sun. Usually a small, bright nucleus (less
than 10 km in diameter) is visible in the middle of the coma. The coma and the nucleus
together constitute the head of the comet.

As comets approach the Sun they develop enormous tails of luminous material that
extend for millions of kilometers from the head, away from the Sun. When far from the
Sun, the nucleus is very cold and its material is frozen solid within the nucleus. In this
state comets are sometimes referred to as a "dirty iceberg" or "dirty snowball," since
over half of their material is ice. When a comet approaches within a few AU of the Sun,
the surface of the nucleus begins to warm, and volatiles evaporate. The evaporated
molecules boil off and carry small solid particles with them, forming the comet's coma
of gas and dust.

Once in a while we will be graced by the presence of a comet that is visible form our
night sky.  I was fortunate enough to be able to image a few from my backyard
observatory.  I have posted images of them here below:

2015

2010

Comet Hartley 2, officially designated 103P/Hartley, is a small periodic comet with an 
orbital period of 6.46 years.  It was discovered by Malcolm Hartley in 1986 at the Schmidt 
Telescope Unit in Siding Spring, Australia.  Its diameter is estimated to be 1.2  to 1.6 km. It 
will be the subject of a flyby by the Deep Impact spacecraft on November 4, 2010, with a 
closest approach of 700 kilometers.  This is part of the EPOXI mission.

Comet Hartley 103P- 10/132010

2007

This comet was discovered by Edwin Holmes on November 6, 1892 while conducting 
regular observations of the Andromeda Galaxy (M31). The comet was undergoing an 
brightened to about magnitude 4 or 5 and then faded over several weeks.brightened to 
about magnitude 4 or 5 and then faded over several weeks.

Comet 17P - 11/13/2007

Comet Holmes - 11/02/2007

Comet Holmes - 10/28/2007

2006

On Jan. 2, 2006 Grzegorz Pojmanski at the Warsaw University 
Astronomical Observatory discovered a faint comet on a photograph that 
was taken on New Year's Day from the Las Campanas Observatory in La 
Serena, Chile, as part of the All Sky Automated Survey (ASAS).  A 
confirmation photograph was taken on Jan. 4.  Later a prediscovery 
image of the comet dating back to Dec. 29, 2005 was also found. 

Comet 177P Barnard - August 22, 2006

Comet Pojmanski - March 11, 2006

2005

    Comet Macholz C/2004 Q2  - January 15, 2005 Images by Dave Trapani

This comet was not as image friendly as NEAT was above.  Therefore, my images 
are not the best quality as I was a little disappointed with them.  I have included one still image and an animation of about 30 minutes below:

Jan 15, 2005

2004

                        Comet C/2001 Q4 (NEAT) - May 19, 2004 Images by Dave Trapani

At the time these images were taken this comet was  about 90 million miles from Earth. 
Traveling at about 50,000 miles per hour, this is the first time this comet has been seen by 
man kind.

May 19, 2004

May 19, 2004