University Lowbrow Astronomers

A Comet Primer and Shades of Hyakutake

by Christopher Sarnecki
Printed in Reflections:  February, 1997.

When discussing a great comet with the public it’s a good idea to get your terms straight.  Useful information never grows old.  The first part of this article is gleaned from an article on comets I wrote almost three years ago.  The second half is on another way to record your observations in a way you probably haven’t thought of.

A typical comet is but a few kilometers across it’s solid head or nucleus.  It has the consistency of a dirty snowball of frozen gases according to the most popular comet formation theory.  When a comet approaches perihelion the nucleus sublimates (evaporates directly from a solid to a gas) and forms a coma - a nebulous, luminescent cloud of gas and dust that may approach the size of the Earth.  A dust tail forms which can extend millions of kilometers, equal to the distance from the Earth orbit to Mars.

A naked-eye comet is a rarity - maybe once (Comet Hyakutake) or twice (Comet Hale-Bopp) in your lifetime.  The rest of the time you will have to be content to use your scope, or binoculars if it’s a bright one.  Following are some tips on how to get a good view of Comet Hale-Bopp:

Here’s some observing challenges:

Here is another exercise to help you enjoy and remember Comet Hale-Bopp.  Record your observations in writing.  Below are my observations of last year’s great Comet Hyakutake:

February 24, 1996
Observed a 7th mag Comet Hyakutake with fellow Lowbrows at Peach Mt. 

March 16th
Messier Night at Lake Hudson.  Cloudy weather brings the night to a close after most observers make it through the Coma-Virgo cluster.  With over 30 observers, seven which were Lowbrows, first observed Comet Hyakutake naked-eye coming over the horizon in Libra.  This is going to be a Great Comet!

March 20th
From Shanty Creek in northern Michigan were I am attending a conference.  Comet Hyakutake is observed with a tripod mounted finder scope.  With the dark skies up here I am almost knocked off my feet by the strong blue color of this comet and it’s five degree tail.

March 22nd
Find my neighbor wandering in my back yard looking for the comet.  “It’s in the front yard” I say.  The clouds roll in almost immediately, but incredibly the comet can be seen through the thinner sections of the clouds with the naked-eye.

March 23rd
Hundreds of people descend on the Lowbrow’s open house at Peach Mt. to catch the comet.  I come to the conclusion that this comet is best enjoyed without any optical aids; but, not before making the biggest mistake of this great comet’s apparition.  In a low powered view through the telescope I notice a “spike” coming out the back of the nucleus.  Embarrassed, I put the scope away thinking I really must collimate the optics.  Later I read numerous reports of a significant but short lived jet or fountain of material leaving the nucleus.  You can bet this is a mistake I will not make again !

March 26th
Comet Hyakutake is at it’s brightest.  It is a Tuesday night and about 25 people show up at Peach Mt.  Many taking photos with their camera riding the 24 inch McMath telescope.  I make a sketch.  Visually the tail extends over 25 degrees !  I learn the definition of “sublime” tonight and am awe struck by the grandeur of the moment.

April 3rd
Observe the comet during a total eclipse from Williamsburg Va. were we are vacationing.  The comet has become a familiar sight in the night’s sky even if it will be short lived.

My last sight of the comet is in the western twilight.  The head of the comet is pointing sun ward and the smaller tail is pointing almost straight up.

When I read these short statements I relive the comet’s passage in my mind and see it as clearly as the night it was observed.


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