Loadstar 128 #26/q26.d81/t.messier

Text File | 1991-01-01 | 6.0 KB | 124 lines

            T H E   A S T R O N O M E R: The Messier Objects

         Data and Text by David Crum -- Program by Fender Tucker


FENDER'S PREMUMBLE:  When David Crum sent me the program he called MESSIER
OBJECTS I saw that it had potential for use by anyone who dabbles in
astronomy as a hobby.  It was basically a dedicated database of information
about the Messier Objects.  The data was well-defined and clear but David's
program wasn't in the LOADSTAR style -- so I rewrote it.  The result is one
of the nicest astronomical "tables" I've seen.  My plan is to use THE
ASTRONOMER as a "shell" into which other astronomy-related databases can be
plugged.  David, and a couple of other astronomy buffs I know, are working
on more projects for the ASTRONOMY Shell already.  Here's David to tell you
about his hobby.


    Every since I was a little boy, I've had an avid interest in astronomy.
About 6 months ago I joined a local Astronomical group and started learning
more about the nighttime sky than I ever knew existed.  One of the more
interesting tidbits of information I learned was about celestial objects
called Messier objects.  As I started learning more about them I decided to
write a program so others could learn about them as well.

    The Messier Catalog is the result.  What it does is it lists all 110 of
the Messier objects and some of their characteristics.  The program will
display in button-like fields the following information for each object:

 (1) the Messier number of the object,

 (2) the common name of the object, (if there is one),

 (3) what constellation the object is located in,

 (4) the New General Catalog number,

 (5) its coordinates using Right Ascension and Declination,

 (6) the apparent brightness (magnitude),

 (7) the distance in light-years.

     Some text books may have different figures for magnitude and distance
but the numbers I have listed are the average.

     Here is a brief history on the Messier objects, how they came about,
and some information on the celestial coordinate system and magnitude
system.

     In the 1770s a French astronomer named Charles Messier was interested
in discovering comets.  To do so, he had to be able to recognize whenever a
new fuzzy object appeared in the sky.  He therefore compiled a list of
about 100 diffuse objects that could always be seen.  To this day, these
objects are commonly known by their Messier numbers.  Messier's list
contains the majority of the most beautiful objects in the sky, including
nebulae, star clusters and galaxies.

    Soon after, William Herschel, in England, compiled a list of 1000
nebulae and clusters, which expanded in subsequent years to include 2500
objects.  Herschel's son, John, continued the work, incorporating
observations made in the southern hemisphere.  In 1864, he published "The
General Catalog of Nebula".  In 1888, J. L. E. Dryer published a still more
extensive catalog, "A New General Catalog of Nebula and Clusters of Stars".
The NGC and later published two supplementary Index Catalogues, or IC's.
The 100-odd non-steller objects that have Messier numbers are known by
them, and sometimes also by their numbers in Dreyer's catalog.  Thus the
Great Nebula in Andromeda is very often called M31, and is less often
called NGC 224.

    The Crab Nebula = M1 = NGC 1952

This information was taken from "Astronomy: From the Earth to the
Universe", Fourth Edition, pg 542, paragraph 3.

    Astronomers mark positions in the sky using coordinates comparable to
those we use to plot positions on earth.  In astronomy, Right Ascension is
celestial longtitude, analogous to terrestrial longtitude.  Declination is
celestial latitude, analogous to terrestrial latitude.  Right Ascension is
marked in hours, minutes and seconds of time, with each 24 hours
representing a full rotation of 360 degrees.  Declination is marked in
degrees, minutes and seconds.  A "+" preceding the number means north of
the celestial equator; and a "-" means south of the celestial equator.
This program does not show the seconds when displaying Right Ascension or
Declination; only hours and minutes or degrees and minutes.

    The information on the coordinate system came from "Peterson Field
Guides: Stars and Planets", pg 202 paragraph 3.

    Astronomers describe the brightness of stars with a scale built on a
historical base.  In the second century B.C. the Greek astronomer,
Hipparchus, classified stars by brightness, and in the first century A.D.
stars were often divided into six classes of brightness.  In about A.D.
140, Ptolemy, perhaps quoting Hipparchus, said that the brightest stars
were of the first magnitude, the next brightest group of stars were of the
second magnitude, and so on.  The faintest stars visible to the naked eye
were of the sixth magnitude.  This scale was placed on a mathematical basis
in the mid-19th century.

     Measurements showed that a difference of 5 magnitudes corresponded to
a factor of about 100 in brightness.  The current magnitude scale is
defined so that a factor of 100 corresponds to exactly 5 magnitudes.  A few
stars are even brighter than first magnitude and have been accommodated by
having magnitudes of 0 and then negative numbers on the scale.  The
brightest star in the sky (other than the sun) is Sirius, whose magnitude
is -1.4.  Canopus, the second brightest, is not visible north of the
southern U.S. and has a magnitude of -0.7.  The sun has a magnitude of -28
and the full moon has one of -12.  Jupiter can have a magnitude of -2.2.

DC

FENDER'S POSTMUMBLE: Now that you have an idea of what the data in the
program means, check out the program itself.  If you're an astronomy buff
you'll find the program a quick way to search for specific objects.  You
can search any of the fields -- except NUMBER, which is not considered one
of the eight fields -- and in some of them you can even search for all
objects within a certain range.  If you have any suggestions for the shell,
or for astronomical topics that may be approached by a database like this,
be sure to let us know.

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