Thursday, 13 May 2010

Don't miss this one: Venus below the crescent Moon on Sunday evening.

See if you can find Venus in daylight!

The very young crescent Moon will be just above Venus (the very bright "evening star") as the Sun sets on Sunday 16th May.  For a few minutes we'll see the pair of them shining brightly in the darkening sky above the colours of sunset.

Start looking for Venus and the Moon as the Sun sets (while the sky is still light).  As the sky darkens, the two will appear to brighten, and then for about ten minutes they'll be high enough above the horizon to be very bright.  As time passes, they'll move downwards, fade away and set.  If you watch this, you're watching the Earth spin - if you're looking towards sunset, you're moving backwards at 1,500 km/hr (one thousand five hundred km/hr).  We don't feel this movement because it's so smooth.

Venus will change colour a bit and "twinkle" as it gets lower - this is because light from objects out in space low in our sky passes through a lot of atmosphere to get to us, and the air in our atmosphere is moving.

Look also for "Earthshine" on the dark part of the Moon - this is sunlight reflecting off the Earth below the horizon in front of you (the part of the Earth that is still having day), back to the Moon.

And while you're out, take a last look at Orion, over to the left of Venus and the Moon.  By the end of the month, our planet will have moved on around the Sun a bit, and we won't see Orion (it will be on the other side of the Sun from us).  Venus however is now catching up with the Earth, and will be our "evening star" for the next few months.

By Monday evening, the Moon will have moved on a bit.  Moon-observing charts for intermediate phase learners can be downloaded from

Starcharts are available at under "In the Sky".


Claire Flanagan

Jhb Planetarium


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