Venus to Shine Bright with Moon, Star Cluster

On these fine spring evenings, Venus shines like a brilliant beacon in the western sky for a few hours after sunset and will soon be joined by a star cluster and a the moon in a weekend sky show. But skywatchers will need binoculars to catch the full effect.

This coming Sunday evening, May 16, Venus will be joined by a slender crescent moon, and the two will frame the beautiful star cluster Messier 35, weather permitting The three will just fit in the field of view of a pair of 7x50 binoculars.

With the unaided eye, you won?t be able to see the star cluster, but the moon and Venus will be a fine sight. This sky map shows where to look to see Venus, the moon and star cluster.

If possible, take a look at the moon with binoculars. You should easily see what is called ?the old moon in the new moon?s arms." [Great moon photos.]

The bright crescent of the new moon is lit almost from behind by full sunlight, while the rest of the moon seems to glow in ?Earthlight" — sunlight reflected off the Earth. If you look carefully, you can see the ghostly outlines of the lunar maria or ?seas? and the bright spots which mark craters like Tycho and Aristarchus.

Just to the right of the crescent moon on Sunday evening is the open star cluster Messier 35 in the constellation Gemini, one of the largest and brightest star clusters in the sky.

This star cluster is about 3,000 light-years away from us, about as far as the farthest stars we can see with our naked eye. It is also almost exactly opposite the center of the Milky Way Galaxy in our sky.

Venus is gradually getting nearer to the Earth.

This week it will be 1.4 astronomical units distant, an astronomical unit being the average distance between the Earth and the sun (about 93 million miles, or 150 million km). In a telescope, it looks like a tiny gibbous moon.

By Aug. 20, Venus will be at its greatest elongation from the sun, and 0.7 astronomical units away, and look like a quarter moon. From there it quickly moves between the Earth and the sun, passing just below the sun on Oct. 29, only 0.3 astronomical units away, and moving into the morning sky.

Even more startling is its change in size, from 12 arc seconds in diameter this week to a full arc minute on Oct. 29, five times larger in diameter. There are 60 arc minutes in 1 degree of the night sky.

For comparison, the full moon in the sky is about 30 arc minutes, or 1/2 a degree, wide. The tip of your pinkie finger held at arm's length could cover about 1 degree.

The next time Venus passes between us and the sun will be on June 5, 2012, when it will actually pass directly in front of the sun as seen from Earth, in what is called a transit.

The last time Venus transited the sun was in 2004, and won?t do it again until 2117, so this will be the last chance to see a transit of Venus in your lifetime.

• Gallery - Venus Crosses the Sun, Part 2
• Venus Seen From Around the World
• More Night Sky Features from Starry Night Education

This article was provided to SPACE.com by Starry Night Education, the leader in space science curriculum solutions.