The dark disk of Mercury seen against the backdrop of the Sun during the transit. The transit is almost over, and Mercury appears near the edge of the Sun. This picture was taken with the Swedish 1 meter Solar Telescope (SST) of the Royal Swedish Academy of Sciences. The telescope is located at La Palma in the Canary Islands.
Click on image for full size
Image courtesy of The Royal Swedish Academy of Sciences.
Mercury Transit on May 7, 2003
News story originally written on July 2, 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, 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
This transit is the first of only 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 on November 15, 1999; the next will
be on November
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. We're in luck though - the next transit of Venus
coming along pretty soon on June 8, 2004!
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 precise time of the transit 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.
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
You might also be interested in:
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
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
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
Here you will find links to all sorts of pictures, animations, videos, sounds, and interactive multimedia that are on Windows to the Universe Explore collections of images in the Image Galleries. Watch...more
Astronomers have discovered a dozen new moons of Jupiter so far in 2003. Scott Sheppard and David Jewitt of the University of Hawaii and Jan Kleyna of Cambridge University led the team of astronomers who...more
On August 27, 2003, Earth and Mars will be closer together than they have been in thousands of years. The centers of the two planets will be 55,758,006 kilometers (34,646,418 miles) apart at 9:51 Universal...more
Astronomers have recently discovered several more moons in our Solar System. Scott Sheppard and David Jewitt of the University of Hawaii and Jan Kleyna of Cambridge University announced the discovery of...more
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