Wandering through the realms of the cosmos, pondering its huge vastness

Posts tagged “august 20 2010 sky

Venus at Greatest Elongation in 2010

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.

Venus at its greatest elongation in 2010

Venus and Arcturus

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”.

it will be brightest in early autumn as it heads back down toward the sun, reaching its peak brilliance for this apparition on Sept. 23 at an eye-popping magnitude of –4.8.  That would make it 23 times brighter than Sirius, the brightest star. Venus then quickly fades, vanishing from view in mid-October, and passes inferior conjunction on Oct. 28.