The final mornings of 2010 (during Dec. 30 and 31) will feature the waning crescent moon with the planets Mercury, Venus and Saturn in the eastern sky before sunrise.
Depending on where you live worldwide, Venus and the moon will rise above the eastern horizon some 3 to 4 hours before sunrise, to light up the wee morning hours until daybreak. For Philippine observers, the screenshot from Stellarium above shows that the Moon – Venus separation is ~20 degrees on December 30, 2010. During this time, the moon will also be ~20 degrees below Saturn. The bright stars Spica in Virgo and Arcturus in Bootes could also be found within this celestial grouping.
Venus is very bright and easy to find. If you look at Venus with a telescope before dawn, you’ll see this planet shining as a wide waxing crescent.
By December 31, the moon and Venus will shine nearly side by side with only 10 degrees of angular separation. Also on this date, Mercury which was in evening dusk during early December will now be in the predawn sky, closer to the horizon. In the screenshot above, it was ~8 degrees above the horizon and ~25 degrees away from Venus. December 2010 provides you with the unique opportunity to catch Mercury in both the evening and morning sky in a single month. Using binoculars will help you see this tiny planet.
Clear skies to all! 🙂
Note: The general rule amateur astronomers use is that the width of your fist from top to bottom held at arm’s length equals about 10 degrees. Read more about this here.
The planet Venus has reached its greatest eastern elongation, or its maximum angular separation (visual distance) from the Sun as observed from the Earth, last August 20. The inferior planets, Venus and Mercury, are best viewed during their greatest elongation. On that night, Venus appeared higher and brighter in the evening sky.
During this appearance, I and my fellow UP AstroSoc member, Andre Obidos saw our nearest planetary neighbor hanging about 20 degrees above the western, an hour after sunset. For comparison, your fist held at arm’s length covers roughly 10 degrees of the night sky.
We were really amazed by its dazzling display during that night. 😀 One may not easily tell that it was indeed a planet. Shining at -4.22, it was the brightest object then, aside from the waxing gibbous Moon. Unfortunately, fainter Mars and Saturn which were lying about a few degrees from Venus were not easily visible.
Below are the images which Andre took.
Last year, Venus, the planet named after the Goddess of Love, reached its peak of brightest just after Valentine’s Day 2009.
If observed through a telescope, it can be noticed that Venus was one half lit by reflected light from the Sun and the other half in dark.
Just like the Moon, Venus has phases. It can be full, gibbous, half or a crescent. These phases occur for the same reason that Moon phases do. One side of Venus is sunlit (the “dayside”). The other side is dark (the “nightside”). As Venus orbits the Sun it turns one side, then the other, toward Earth. At the moment, Venus is turning its nightside toward us. We can see only a sliver of the dayside–hence the crescent.
In one way Moon-phases and Venus-phases differ: The Moon is bright when it’s full, and dim when it’s a crescent. Venus is just the opposite. It reaches greatest brilliancy at crescent phase. When it is “full”, it is not normally possible to observe Venus because it is then on the other side of the Sun. Strange but true. 😀 (useful diagrams and explanations here)
By October 2010, Venus will end its reign as it goes lower and lower in the sky. It will reach its peak magnitude of -4.6 on September 24, about 23 times brighter than Sirius, the brightest star. But in mid-October, Venus will dim to -4.3 and will set with the sun until it passes inferior conjunction on Oct. 28. In November, it will enter the dawn sky as the “Morning Star”.