Shop Windows to the Universe

Ready, Set, SCIENCE!, by the National Research Council, focuses on K-8 science classsrooms. Check out the other publications in our online store, as well as classroom materials.

Mercury Transit on November 8, 2006
News story originally written on November 6, 2006

The planet Mercury will cross in front of the disk of the Sun on Wednesday, November 8, 2006. Astronomers call the event a transit. A transit is similar to a solar eclipse. However, a transit occurs when a planet, instead of Earth's Moon, passes between the Sun and Earth. Because planets are so much further away than the Moon, the planet does not completely cover the Sun during a transit like the Moon does during most eclipses.

This transit is the second of just 14 transits of Mercury during the 21st century. On average, transits of Mercury occur about once every seven years. The most recent previous transit of Mercury was only a few years ago on May 7, 2003. However, the next Mercury transit won't be until May 9, 2016!

Only two planets, Mercury and Venus, ever transit the Sun as viewed from Earth. All of the other planets orbit the Sun further from Earth, and thus never pass between Earth and the Sun. Since the orbits of the planets are tilted, transits occur only some of the times when Mercury or Venus pass between Earth and the Sun. Usually the planets pass above or below the Sun as viewed from Earth, instead of directly crossing in front of the Sun.

Transits of Venus are much rarer than transits of Mercury. Venus transits happen only twice per century. You may have been lucky enough to view the last one, which occurred on June 8, 2004. In case you missed it, there will be another on June 6, 2012.

Astronomers in the 1700's used transits of Venus to make the first accurate measurements of the distance between Earth and the Sun. By noting the angle between Venus and the Sun as viewed from different locations on Earth and by using their knowledge of the way planets orbit, astronomers were able to calculate the distance to the Sun. Sir Edmund Halley, of comet fame, was the first astronomer to realize that transits could be used to make that calculation.

Last modified November 6, 2006 by Randy Russell.

Shop Windows to the Universe Science Store!

Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Transit

A "transit" is the name of a type of astronomical event. A transit is similar to a solar eclipse, except a transit involves a planet, instead of the Moon, passing in front of the Sun. As viewed from Earth,...more

Mercury Transit on May 7, 2003

The planet Mercury appeared to cross in front of the disk of the Sun on May 7, 2003. Astronomers call the event a transit. A transit is similar to a solar eclipse. However, a transit occurs when a planet,...more

Transits of Venus

The planet Venus periodically passes directly between Earth and the Sun. This event, which is somewhat similar to a solar eclipse, is called a transit of Venus. Viewed from Earth, Venus and Mercury are...more

History of Venus Transits

Transits of Venus are extremely rare astronomical phenomena. They occur in pairs, separated by eight years, with more than a century elapsing between successive pairs of transits. There will be two Venus...more

Venus Transit in June 2004

A rare astronomical event will occur in early June 2004. For the first time since 1882, Earthlings will be able to view a transit of the planet Venus. "Transit" is a term used by astronomers when a planet...more

Mercury Transit on November 8, 2006

The planet Mercury will cross in front of the disk of the Sun on Wednesday, November 8, 2006. Astronomers call the event a transit. A transit is similar to a solar eclipse. However, a transit occurs when...more

More than 100 planets orbit distant stars!

Astronomers have identified another exoplanet, that is, a planet outside our solar system. This makes a total of 102 exoplanets that have so far been found by astronomers! The astronomers that identified...more

Map of the Sky

Thanks to a couple of telescopes, everyone on the internet can browse through almost 2 million images. Stars throughout the sky were photographed by the Two-Micron All Sky Survey (2MASS) and are now available...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA