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Look high above the western horizon to locate Jupiter, the
brightest object in the night sky (after the moon) and the dominant
planet of our Solar System. Its distance can be represented as about
35 'light minutes', as that is how long it takes light to travel from
Jupiter to us. The bright reddish star seen not far from Jupiter is
Antares, the brightest star in the constellation of Scorpius. Yet
Antares is more like 600 light years distant, a highly luminous
swollen red giant star. Still beyond Scorpius and its neighbouring
constellation of Sagittarius, lies the luminous band of the Milky Way,
the giant spiral galaxy we inhabit seen from within. Much of the
luminosity you see in this direction comes from unresolved stars in
the Sagittarius Spiral Arm about 5000 light years distant. Further
still, but largely hidden by foreground dust clouds is the centre of
the Milky Way Galaxy 25000 light years away. In the same way as our
Earth orbits the Sun, so our Sun and its Solar system orbit around the
centre of the Galaxy, but one orbit takes 200 million years!
The Moon is in the evening sky from September 13.
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