GONG network to broadcast the transit of Mercury on Nov. 8, 2006

Press Release From: National Science Teachers Association
Posted: Monday, November 6, 2006


CAUTION: It is exceptionally dangerous to view the Sun without the right equipment. Blindness or painful, permanent eye damage will result.

Tucson, Nov. 6, 2006: A global network of telescopes designed to watch the Sun's vibrations will be used to broadcast the upcoming transit of Mercury across the Sun on Wednesday, November 8, 2006.

Transits occur when Mercury or Venus passes between the Earth and the Sun. The timing is complex and depends on the relative motions of Earth and the other planet. Mercury transits occur in May at intervals of 13 and 33 years, and in November at intervals of 7, 13 and 33 years. GONG observed the last two transits of Mercury on November 15, 1999 and May 7, 2003, as well as the Venus transit on June 4, 2004. Venus transits are less frequent and have occurred only seven times in the last four centuries. The next Venus transits will be in 2012 and 2117.

Transits once were the most valued of astronomical events, a rare chance for astronomers to size up the solar system. The distance from the Earth to the Sun can be estimated by measuring either the exact position of a transiting planet on the disk of the Sun or the precise time that the planet touches the solar edge as seen from widely separated locations on the Earth. While we now have more accurate methods for measuring the Sun-Earth distance, transits allow school classes to apply the original technique. This is an opportunity to involve science teachers and students in studying both the Sun and mathematics and for everyone to appreciate this rare and spectacular cosmic happening. Today, transits are used for a variety of scientific purposes, ranging from studying the atmosphere of the transiting planet to measuring the alignment of the telescope observing the transit.

The observations will be made by the National Science Foundation's Global Oscillation Network Group (GONG). The National Solar Observatory operates GONG under contract to the NSF. Four of GONG's six telescopes will record the silhouette of Mercury as it crosses in front of the Sun. The observations will be made by GONG telescopes located in Australia, Hawaii, California, and Chile. The images will be updated every ten minutes on the Internet, and a movie of the event as seen from each of the four sites will be constructed as the transit progresses. Please note that Mercury will be too small to observe with the unaided eye, and that it is exceptionally dangerous to view the Sun without the right equipment. Blindness or painful, permanent eye damage will result.

Depending on the time zone, the transit begins at: 2:12 pm EST, 1:12 pm CST, 12:12 pm MST and 11:12 am PST (9:12 am in Hawaii). The transit ends at 4:10 pm PST (2:10 pm in Hawaii). The GONG sites at Big Bear, California and Mauna Loa, Hawaii will observe the entire transit. The site at Cerro Tololo, Chile, will observe the start of the transit but not the end as the Sun will set in Chile while the transit is still going on. Similarly, the site in Learmonth, Australia, will see the Sun rise with the transit already in progress.

The web page for the GONG transit images is located at The page contains links to other transit sites. A composite image of the 2003 Mercury transit as observed from the GONG site in Udaipur, India, is shown below. Mercury is the string of small black dots across the upper part of the Sun. The other features on the disk are images of sunspots that have been smeared by the Sun's rotation during the transit.

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