The planet Mercury made a cameo Wednesday, Nov. 8, 2006, on telescopes across the world as it crossed between the sun and the Earth, an occurrence that only happens about 13 times a century.

The solar transit was viewable on BYU's telescopes for five hours as the small planet passed, almost unnoticeably across the huge solar disc.

"The fact that we can predict down to the second when it is going to cross is pretty amazing," said SummerDale Beckstrand, an undergraduate majoring in physics and astronomy. "It means our numbers are right on."

Mercury is only slightly larger than the Earth's moon, but has a highly irregular orbit around the sun. Visible only on specially filtered telescopes during its transit, the planet appears roughly the size of a pinhead crossing over a basketball.

While to the untrained observer, solar transits may appear inconsequential; Mercury's solar crosses have provided scientists with valuable information about our planet's location in the solar system.

"It has something to do with spherical geometry," Beckstrand said. "As they observe Mercury as it passes by the sun they can calculate exactly how far we are from the sun."

Venus is the only other planet we can observe passing in front of the sun, but according to NASA, Venus only transits every century or so.

"It's a once in a lifetime thing to see Venus," said Tabitha Bush, a graduate student studying physics. "But, it's all a matter of perspective, planets cross in front of the sun all the time, we just can't see them."

Bush was assigned the role of watching over the outdoor telescope atop BYU's Eyring Science Center and managing the steady line of students who came to take a peek.

"Last time this happened, the roof was overrun with lines going down the stairs," Bush said. "I guess this time it wasn't quite as publicized."

For those who missed the solar spectacular, Mercury is scheduled to pass the sun again in 2016 and Venus in 2012.

Copyright Brigham Young University 8 Nov 2006