Written by Kelly Herbst, Astronomy Curator for the Virginia Living Museum. Updated every two weeks, more or less.

Wednesday, May 30, 2012


Red alert!  Red alert!  All hands to battle stations!

Hee hee, I've always wanted to say that.

Okay, seriously...I'm posting a special update to make sure all of you out there in internet land are aware of the incredible astronomical event taking place next Tuesday.  On the late afternoon/early evening of June 5, we have our last opportunity to witness Venus cross directly in front of the Sun.  Such events are called transits of a planet, and this will be the last one Venus will consent to do in our lifetimes...unless any of us plan on living 105 more years (Adam Savage excepted, of course).

So what is it we are going to see on June 5th?

The 2004 Transit of Venus.  Photo by Jay M. Pasachoff.

Venus orbits the Sun closer in than we do.  It's the second planet from the Sun...we're the third.  So on June 5th everything is going to line up just right to allow us from here on Earth to see Venus silhouetted against the solar surface.  Normally, this doesn't happen.  The solar system is not perfectly aligned - everybody is just slightly off kilter - and so usually Venus passes above or below the visible surface of the Sun from our perspective.  Mercury can do this too - it's the closest planet to the Sun, and moves faster than Venus, so the alignment works more often.  But Mercury is much smaller than Venus (and in fact, smaller than several of the larger moons of the solar system), making it much more difficult to see against the solar surface.  Venus is bigger and closer to us, so the perfectly round black dot of Venus will visible to the unaided (BUT NOT UNPROTECTED!!!) eye.

Notice the yelling up there?  Please, please, do not attempt to Venus the transit of Venus without proper eye protection.  This can result in PERMANENT eye damage.  Sunglasses are not enough, nor is it safe to look at the solar surface during sunset when the Sun is red.  The only safe ways to view the transit are by projecting an image of the Sun, protecting your eyes with solar eclipse glasses or shade #14 arc welder's glass, or using an endcap solar filter on your telescope.  Any other method can be terribly dangerous, so please don't attempt it.  If you're not sure if you have the right equipment to safely view the Sun, contact us at the museum.  We can help.

Okay, so what's the big deal?  A dot on the solar surface.  So what?

So what!!!???!  It's AWESOME!  You're watching a planet cross in front of its star!  WOOT!  That would be the geek explanation of why this is so cool.

Historically, transits of Venus gave us a yardstick by which to measure the sizes and distances of our own solar system.  If you can measure the size of the disk of Venus against the size of the disk of the Sun, and measure how long it takes for Venus to cross the disk of the Sun, you can use that information to calculate a whole bunch of things...most importantly, the distance between the Earth and the Sun.  Since getting out your tape measure and walking to the Sun is...well...highly problematic...transits of Venus gave us the best way of measuring distances in the solar system prior to spaceflight capabilities.

In the 21st century, we've become very interested in planet transits...around other stars.  The Kepler telescope looks for the tell-tale drop in brightness from stars that have planets crossing in front of them, as the planet prevents some of the light from the star from reaching the telescope.  The transit method has allowed us to discover numerous other solar systems in our galaxy...and perhaps one day will aid in us finding another Earth-like planet somewhere out there.

NASA's Kepler Mission.  Courtesy NASA.

If you're looking for some help in viewing the transit, we've got you covered.  We're hosting a special "Dinner with Venus" event, as the transit will begin around 6pm and continue well past sunset (of course, we won't be able to see the Sun after that, so our viewing will be over).  Tickets are $30 per person and include an all-you-can-eat dinner buffet at the Wild Side Cafe, eclipse glasses, telescope viewing of the transit (or internet viewing if the weather goes bad), prize drawings and more.  Space is limited, so contact us today to reserve your spot.  And if you can't get here - get outside on June 5 and watch the sunset with PROTECTED eyes - you'll get a bit more than you bargained for!

Carpe diem et noctem!


  1. Kelly, can we purchase solar eclipse viewing glasses from the VLM?

    1. Sadly, no, our gift shop does not carry them. And the weather today is not exactly being helpful. However, you can check out the transit in its entirety at:
      Good luck!


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