Capricornus, not Capricorn
is the name of the
Zodiac constellation that can be found low in the south during
evenings in autumn. Astrologers may call it Capricorn, but astronomers
do not. Astrology was a way of life, though, until the times when
men were able to use more than just their imaginations to study
the heavens. And after all, you can call any group of stars anything
you like; you can even pay to have stars named whatever you want,
and for your money they will put your name in a book in a bank
vault in Switzerland, or whatever they say they’ll do. None
of these star-naming schemes is official, however, and the names
won’t be known to any astronomers. Think carefully before
you pay your money, but this is usually an honest way for some
people—even legitimate astronomy groups—to sell their
imagination.
When, thousands of years ago, the ancient peoples of Babylon and
Chaldea looked to a certain portion of the sky they imagined it
as akin to the sea. Without many bright stars that region seemed
vast as the oceans, stretching beyond their view. The fascination
with the sea led to sky stories of wondrous creatures such as
the goat-fish that later became the symbol of Capricornus.
Some say the symbolism came from India, where the stars of Aquarius
were the first of their zodiac. Its patron god was Varuna, the
all-powerful lord of the sky and creator of the stars. He rode
through his starry realm on Makara, his fabulous steed, half crocodile
and half bird, who was equally adept on the sea as in the air.
As Varuna, represented by Aquarius, eventually lost his claim
to the sky and became just the god of the oceans, so Makara, represented
by Capricornus, also lost his identity and became half fish and
half ibex, or wild goat [Capra ibex]. The name Capricornus
actually means ‘horned goat’ in Latin.
Sargon, a Babylonian founder of about 2800 BC, left records foretelling
the fiery destruction of the world should all the five planets
appear at the same time in the sign of Capricornus. Such an event
actually occurred, according to Chinese astronomers, in the year
2449 BC. No blazing conflagration was reported.
October is a fine month for observing Capricornus. Find what appears
to be a wide arrowhead, pointed downward, by following to the
south and east the line of the three bright stars in Aquila.
Capricornus places second to Cancer among the zodiac constellations
in faintness. No stars are brighter than third magnitude. The
brightest star in the constellation is Deneb Algedi, from the
Arabian for ‘tail of the goat.’ Its magnitude is 3.1.
About equally bright at 3.2 is Algedi, Alpha Capricorni. This
is an optical naked-eye double; the brighter, Alpha-2, is 100
light-years distant, with Alpha-1 about 500 light-years away.
The chance alignment places them just over six minutes apart along
our line of sight. Each of these stars is multiple. These stars
were studied in 1862 by the renowned telescope maker Alvan G.
Clark, whose firm made Chabot’s 8-inch refractor in 1883
to the order of founder Anthony Chabot. In 1913 this magnificent
telescope was given the name Leah by Chabot Observatory
Director Charles Burckhalter.
NGC 6907 is a barred spiral seen
nearly face-on. It is just a fuzzy spot (mag. 11.3) in a small
telescope.
Image courtesy of Steven Williams, Grove Creek Observatory in
Australia.
<www.gco.org.au>
There are few deep-sky objects of note for small telescopes. M30
is the only Messier object, a globular cluster of magnitude about
7.5 and with a diameter of eleven minutes. Messier discovered
the faint cluster in 1764, using a small reflecting telescope
of aperture equivalent to two inches. Concluding it to be a nebula,
he could not resolve the fuzzy patch into stars; and it was left
for Sir William Herschel with his far better optics 19 years later
to describe the cluster in detail. The cluster has been found
to be about 40,000 light-years away.
The discovery of the planet Neptune is one of the more interesting
tales of modern astronomy. Following the discovery in 1781 of
Uranus, Herschel’s ‘George’s Star,’ the new
planet was found to have an uneven motion. Speculation suggested
that yet undiscovered planet was perturbing the orbit in a minute
but ‘intolerable’ way. John Couch Adams, an undergraduate
at Cambridge, undertook the problem and in 1845, after two years
of calculations, sent a prediction of the location of a ninth
planet to Astronomer Royal Sir George Airy. Nothing was done to
follow up Adams’s work. Meanwhile, Urbain J. J. Leverrier
in France independently solved his equations and sent his solution
to Johann Galle in Berlin. Galle immediately pointed his telescope
to the predicted position. With the help of a graduate student,
Heinrich d’Arrest, he found an eighth-magnitude ‘star’
that was not on the best available star map. On closer observation
Galle discerned the object to have a small disk. The planet was
within a degree of Leverrier’s prediction in Capricornus,
near Deneb Algedi. Joyously, Leverrier suggested that the planet
be called Leverrier. His second choice, Neptune, was adopted
instead. It seems a fitting name for a planet that appears sea-blue
in color, and which was first imagined to exist—and then
was discovered—in a constellation of the sea.