A twice in a lifetime event (at best) is coming up next month. Late in the afternoon on Tuesday, June 5 the planet Venus, which for the past six months has been the most brilliant “star” in the western sky just after sunset, will begin to pass directly between the Earth and the Sun. This perfect alignment will allow viewers in Pennsylvania to see the planet’s silhouette move across the surface of the Sun – known as a transit. Transits of Venus are rare, they occur in pairs, eight years apart and then not again for more than 100 years. The next transit of Venus will be in 2117. So if you missed it in 2004, now is your last chance to see a transit of Venus in person.
Please take care! Directly observing the sun can cause permanent eye damage. Never look directly at the Sun – viewing the transit should be done only by projecting the image or using approved filters. Weather permitting, we will have telescopes outfitted for safely viewing the transit at the Sis and Herman Dupré Science Pavilion beginning at 6pm on June 5, 2012.
The image above, taken by Pittsburgh Post Gazette photographer V.W.H. Campbell Jr., captures the last transit of Venus from the roof of the Physics building in the early morning on June 9, 2004. Venus appears as a dark disk to the left hand edge on the orange projected image of the rising sun.
While this is only the seventh transit of Venus since the invention of the telescope, these rare events have been important to astronomers. The first coordinated observations of transits across the globe allowed the distance between the Sun and the Earth to be calculated most accurately. Other astronomers deduced that Venus had a thick atmosphere by watching the transit. Most recently, the transit of Venus in 2004 was used to refine techniques to detect planets around other stars (see The First Earth-like Planet beyond the Solar System?!).
Not nearly as rare, the Perseid Meteor Shower occurs each August. This year promises to offer good conditions around its peak on August 13. We see a meteor shower when the Earth passes through the orbit of a comet. Debris from the comet litters the orbit. When these small particles hit the Earth’s atmosphere at a relative velocity around 15 miles per second, observers on the ground see a bright, fast-moving vapor trail as the shock of the collision disintegrates the ancient piece of ice or rock. This year the Moon will not be in the sky most of the night allowing more of the meteors to be seen without the obscuring glare from the Moon. We are planning a public viewing on campus for this year’s Perseid meteor shower peak.
For information on these special events and our regular public planetarium shows, check out the Angelo Taiani Planetarium and Astronaut Exhibit web page periodically (http://www.stvincent.edu/planetarium/).