ARTICLES
Observation Studies of Constellations in the Earth and Space (continued)
July – September
forms the bottom end of the ‘cross’. It looks like a single star,
but is in fact a multiple star with as many as 6 component stars
forming its ‘family’. Gamma Crucis (also known as Gacrux) is the
orange hued star at the top of the ‘cross’. Gacrux is one of the
nearest red giants to our solar system, but at about 88 light years
it is hardly a close neighbour. Beta Crucis forms the left arm of the
‘cross’. Also known as Mimosa, this is a rather large white-blue
star, believed to be a multiple star. Delta Crucis forms the right
arm. Epsilon Crucis is the orange star between Alpha and Delta.
All of these stars are believed to be very young, perhaps less
than 20 million years old. On a clear night watch for a dark patch
between Beta and Alpha Crucis: that is the Coalsack Nebula.
The faint, hazy object just to the left of Beta Crucis is the Jewel
Box, which binoculars or a telescope will reveal to be a small
cluster of very young stars.
Winter is perhaps the most exciting time for observation studies of
constellations. Many bright constellations cross the sky, as does
the Milky Way. Scorpius, also known as Scorpio, is not hard to
miss because of its distinct shape, resembling a scorpion. You
will find Scorpius rising in the east in early July at sunset and
almost overhead by 9pm. Photo 5 was taken at around 7pm in
early July.
Back to the pointers, part of Centaurus but often associated
with Crux: the pale yellow star on the left is Alpha Centari. Alpha
Centauri is the third brightest star in the sky. It is a triple star
system comprising the nearest stars to our own Sun, being just
over 4 light years away. Proxima Centauri, part of this system, is
in fact the closest star to our Solar System. Beta Centauri, on the
right is another triple star system comprising blue giants, hence
the colour.
Photo 5: Scorpio rising in July
From the Southern Cross turn 180 degrees and you will find Leo,
another constellation of the zodiac. Leo has fainter stars than
Crux so a referral to a star chart is recommended, but once you
do find it you will notice that the ‘lion’ is appearing to leap through
the sky upside down. Photo 4 is a scan of a picture taken some
time ago. The brightest object, top right is Alpha Leonis, also
known as Regulus. The bright star in the bottom right corner is
Beta Leonis, also known as Denebola. There are faint objects
to be found along the line between these two stars. Binoculars
will reveal small fuzzy bluish objects. A more powerful telescope
reveals that they are spiral galaxies.
The head of the ‘scorpion’ is the three stars in a bent row at top left
corner of the photo. The tail is at the bottom right. Perpendicular
to the head lie three stars in a slight curve. The orange hued star
in the middle is Alpha Scorpii, commonly known as Antares. This
is a red supergiant so big that it would almost reach the orbit of
Jupiter if it was in our Solar System. It is often mistaken for planet
Mars because of its similar colour. Astronomers think that this
star may explode as a supernova perhaps in a few thousand
years’ time.
The star above and left of Antares is Sigma Scorpii. Between
these two stars lies the M4 globular cluster, which can be seen as
a fuzzy haze on clear nights. Two fuzzy objects that can be seen
just below the tail of Scorpius are the M6 and M7 star clusters. All
three clusters are quite fascinating to observe through binoculars
because of the many stars of many hues to be found there. Indeed
a sweep of the ‘body’ of Scorpius will reveal many colourful star
clusters.
Sagittarius follows Scorpius rising in the eastern sky at this time
of the year, located just under the tail of the scorpion. The key
star pattern is two trapezoid shapes at angles to one another
followed by a wide triangle of stars below. Picture 6 illustrates the
positioning of both zodiac constellations in the evening eastern
Photo 4: Leo in June
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SCIENCE EDUCATIONAL NEWS VOL 68 NO 4