My Dark Sky

If you are wondering what’s that two very bright stars in the west after sunset were, congratulations, you had just witness one of the many beautiful scenes in the sky (a scene which I’m longing to see but was not allowed by the weather…)

The two bright “stars” are not stars – they are the planet Venus and Jupiter. The upper one is Jupiter whereas the one nearer to the horizon is Venus. If you are trying to remember who is on top or who is at the bottom, don’t bother… because they are going to change their position soon anyway. Just know that the brighter one is Venus (magnitude -4.2) and the relatively dimmer one is Jupiter (magnitude -2.0).

In the days to come, Venus will be climbing higher and higher to meet its big brother, until they are only 2 degrees apart on December 1. The best thing is a crescent Moon will be joining them too, making this conjunction a beautiful scene in the sky, backdropped by the constellation Sagittarius. The positions of the two planets and the crescent Moon form a smiley face in the sky (for Asia). Find a nice foreground to add to the scene, and you can capture the beauties of the sky.

The positions of Venus (left), Jupiter (right) and the crescent Moon form a smiley face in the sky on December 1 (for Asia).  Click the image for animation of the planets’ positions from November 26 to December 4.

After the meeting, Venus will continue to climbs higher, while Jupiter will dip lower and lower into the horizon. These motions are due to the relative motion of us and the planets. Venus, being an inner planet, circles the Sun faster than we do, so it’s “catching up” with us and moves away from the Sun. The outer planet Jupiter, on the other hand, orbit the Sun slower than us, so it’s lagging behind toward a position behind the Sun. Jupiter will remains in Sagittarius whereas Venus will move through Capricornus and ends the year in Aquarius.

Apart from the Sun and the Moon, Venus and Jupiter are the brightest objects in the sky, even brighter than the brightest star in the night sky, Sirius. To find them, just face west after sunset and there they are. They are shinning so brightly that it’s not difficult at all to see them – it’s more difficult not to see them.

Although naked eye view is all you need to enjoy the scene, a view through binocular or telescope can give different experiences. On December 1, our Moon and the two planets will be visible together in your binoculars, an unforgettable view indeed! A look through telescope with the same eyepiece will give a feel of how big Jupiter is. The giant planet, although lies 6 times farther away, appears twice as big as Venus.

Through a telescope, observe the phase changes of Venus. Venus will go through phases just like our Moon because of its orbit that are between us and the Sun. Apart from it phases, that is nothing much to see on Venus – it is featureless due to the thick clouds that enshroud the whole planet.

However, a different story goes for Jupiter… the giant planet’s atmosphere is full of features. The most prominent one is the two dark bands on either side of the equator. The dancing of its four largest moons around it is also fun to observe. But as the planet dips lower and lower into the horizon, it has to go though more and more of our atmosphere – most of the features will be lost to the atmospheric turbulences.

Finally, don’t forget the date with our Moon and the two brightest planets on December 1… and clear skies to everyone out there!

~ by thChieh on November 27, 2008.

Posted in Observations & Tips