These photographs show the transit of Venus across the sun on June 5, 2012. This rare event occurs when Venus passes in front of the sun from the perspective of viewers on earth. The photos were taken by members of the Black Hills Astronomical Society at an event hosted by the BHAS at the Journey Museum in Rapid City. There was also a streaming of the transit from Badlands Observatory which was projected onto the screen in the museum auditorium.
Venus transits occur four times every 243 years, with a pair of transits 8 years apart, an interval of 105.5 years, another pair 8 years apart, and another interval of 121.5 years. The last transit was June 8, 2004 (but was not visible here) and the next one will not occur until December 10, 2117, followed by one on December 8, 2125 and so on. The event is rare due to the differences in the inclination of the orbits of the earth and Venus, as well as the speed of the planets as they move around the sun. (Dates given in Mountain Standard Time.)
By carefully measuring the duration of a Venus transit as viewed from two widely spaced locations on earth, eighteenth century astronomers were able to mathematically determine the distance from earth to the sun (known as the astronomical unit). Once this distance was known, Kepler's laws of motion could be used to find the distances to other planets and even some of the stars closest to our solar system.
Transits across the face of the sun by Mercury are more frequent than transits of Venus. For Rapid City viewers interested in transits by Mercury, the following dates will be of interest: May 9, 2016 (transit in progress as the sun rises), and November 11, 2019 (transit in progress as the sun rises). The transits in November of 2032 and 2039 will occur in the middle of the night for viewers in the United States. [Corrected 6/26/2015]
NOTE: Transits of the sun are rare events. However, if you wish to observe the sun for whatever reason, it is imperative that you observe the proper precautions to prevent sudden and permanent damage to your eyes. Click here for more information about this.
The image below was made by hand holding an ordinary camera up to the eyepiece of a telescope. The blur seen on the left is an artifact from the misalignment of the optical systems involved.
As before, the image captured using a hand-held camera and a telescope is far from perfect. In addition, the local weather often blocked our view. You can see in this image some of the less obtrusive clouds that were experienced that afternoon. At times, nothing could be seen of the sun.
The image below was created by Dr. Don Teets who observed the transit at Phoenix, Arizona.
The computer-generated diagram below shows the path of the planet Venus across the sun, as seen from Rapid City. The path of the center of Venus from 4:04:23 PM MDT to 8:08:09 PM is shown as a curved line because the view of the sun changes orientation as the sun moves across the sky. The simulation was stopped, as shown here, when the sun was near (3 degrees) the horizon; the direction of the view at that time was 299.2 degrees (WNW).