Reports - 2013
Astronomy Benalla Meeting Presentations - Wednesday 20th November 2013
Constellation of the Month - Taurus Presenter: Jeff Knight
As summer approaches, the wonder of our southern skies continues to enthral us. As a young lad I remember vividly,
gazing up at the beautiful black backdrop of the summer sky for nights on end. I would try and make out patterns by
‘connecting the dots’; the bright pinpoints of light. I knew nothing of the constellations back then, but some asterisms,
like the ‘Saucepan’, just hit you. As did the ‘Rocket’, just left of the Saucepan, and the ’Seven Sisters’ just beyond
that.
Of course it wasn’t really a ‘rocket’, but to my eye it later became a very useful reference point for finding the
constellation of TAURUS. The upside down ‘V’ was the very snout of the Bull. In time I would learn that this was
actually an open star cluster known as the Hyades, and pronounced very similarly to that of the Pleiades, the more
well-known and beautiful open star cluster, universally known as the ’Seven Sisters’, and situated in the left shoulder
of the charging bull.
I deliberately have to force myself to see these pictures
upside down in the night sky, as most books and
periodicals usually show these constellations from the
northern hemisphere (and certainly ‘original’!)
perspective. Taurus’ mighty horns therefore extend down
toward the horizon, as marked by the second brightest
star in this constellation, El Nath (“The Butting Horn”).
The principal star of Taurus (alpha Tauri) is the very eye
of the bull, known in ancient times as ‘Al Debaran’ (‘The
Follower’, because it followed the Pleiades presumably!),
and by even earlier names, ‘I-ku-u’ (‘Leading Star of
Stars’), ‘Gis-da’ (‘Furrow of Heaven’), and ‘Dilgan’
(‘Messenger of Light’). It is a fiery orange giant over
forty-four times the diameter of our sun, and just over 65
light years away. While it appears, from our perspective,
to sit supremely in the Hyades open cluster, it is in fact completely unrelated to the cluster, sitting about half way
between us and them.
When considering this orange giant, I can’t help but wonder whether the term “Bulls Eye” may have been coined in
antiquity after the famed Al Debaran, the eye-catching, focal centre of Taurus!
As a child I particularly marvelled at the beauty of the ‘Seven Sisters’ (being so near to the ‘Rocket’), although I really
could only count six. I learned in time that it was a cluster of possibly over one thousand stars, and that people with
exceptional eyesight could see up to eighteen in the right conditions. When I inherited my first pair of binoculars, this
was definitely one of the first objects on my ‘must see’ list. I was not disappointed! Through my 7 x 50’s the Pleiades
looked like the most beautiful collection of jewels I had ever seen; and, not only could I see the ‘seventh sister’, I could
now see scores of her family.
What I particularly find intriguing is that in every
culture this star group is known by virtually the
same name. Even our Australian aborigines
cite a legend where the ‘missing’ queen was
snatched away by a crow infatuated with her
beauty. They didn’t have the benefit of our
viewing equipment, so how did they know there
was another?
Caleano, in Greek mythology, is known as ‘the
lost pleiad’, as it is too dim to be seen with the
naked eye.
Taurus is unique among the zodiacal constellations.
It alone sits in that part of the heavens where it is
crossed by all three of the ‘galactic equator’ (the
plane of our galaxy), the ‘celestial equator’ (the
projection of the earth’s equator onto the heavens),
and the ‘ecliptic’ (the path of the sun across the sky
from our perspective).
It also hides a number of deep sky objects that are
worth seeking out (though some of these are only
discernable through the ‘Hubble’!).
The most famous of these is the Crab Nebula (M1), situated near the tip of
the bull’s right horn. Lying around 6000 light years from us, it appeared as a
bright explosion in 1054 AD, according to ancient Chinese chronicles, and
could be seen even in the daytime for twenty-three days before it
disappeared. Charles Messier’s observation of it, in 1758, stimulated him to
compile his Messier List, being the first entry, M1.
The Crystal Ball Nebula (NGC 1514) is a planetary nebula about 4
degrees below the rising Pleiades. It was discovered by William
Herschel in 1790, describing it "A most singular phenomenon" and
forcing him to rethink his ideas on how the heavens were
constructed. As a result, he came to understand that the ‘cloudy’
nebula was not at all made up of masses of stars too remote to
resolve, but rather was a “faintly luminous atmosphere".
The Merope Nebula [Tempel’s Nebula] (NGC 1435) is located in the Pleiades
star cluster. It surrounds the star Merope (23 Tauri) and is illuminated by the
star’s light. The nebula is a suspected supernova remnant, and was
discovered by the German astronomer Wilhelm Tempel in 1859. It is
approximately 440 light years distant from us.
Hind’s Variable Nebula (NGC 1555) is another ‘reflection’
nebula, like that of Merope, but it exhibits variations in luminosity
as a result of changes in its star. It lies 400 million light years
away, beside the star T Tauri, (very near the left ‘eye’ of Taurus)
and is illuminated by the star’s light. The nebula was first
discovered by the English astronomer John Russell Hind in 1852.
NGC 1409 (right) and NGC 1410 (left) are a pair of colliding
galaxies 300 million light years from us. They are to be found just
above the (upside-down!) left hoof of Taurus. The two galaxies are
connected by a pipeline of gas spanning over 20,000 light years
that is being funnelled from one galaxy to the other. They are
gravitationally bound and will eventually merge into one.
Prepared, with special acknowledgement to:
Wikipedia
Constellation Guide
Starry Night Enthusiast
CosMos Astronomy
EarthSky, Science news
Star Names, Richard Hinckley Allen, 1889
CoraSkywalker's Blog
Anne‘s Astronomy News
