Press Release Images for the June 5-6 Transit of Venus

Venus transits the Sun

S&T contributing photographer Babak Tafreshi shot this photo of Venus transiting the Sun in 2004. (Click on the image for a high-res version.)

 

Where to see the transit of Venus

For most of North America, the transit of Venus will begin on the afternoon of June 5th and still be in progress at sunset. Those in western Pacific, eastern Asia, and eastern Australia see the whole show from beginning to end on June 6th (local date). (Click on the image for a high-res version.)
Credit: Michael Zeiler / Eclipse-maps.com

 

Close-up of 2004 Venus transit

This close-up of Venus perching on the Sun's limb was shot using a webcam on a 16” Zeiss refractor, stopped to 12” with a solar filter. The very faint arc on the left side of Venus is probably due to sunlight refracting through the planet’s upper atmosphere. (Click on the image for a high-res version.)
Credit: S&T / Dennis di Cicco

 

"Black drop" effect

Australian watchmaker F. Allerding recorded the “black-drop” effect as the silhouette of Venus prepared to exit the Sun’s disk on December 9, 1874. He observed through a 3½-inch refractor. Adapted from Observations of the Transit of Venus Made in New South Wales by Henry C. Russell (Sydney, 1892). (Click on the image for a high-res version.)
Courtesy Institute for Astronomy, University of Vienna.

Transit of Venus diagram

Transits of Venus can only occur when Venus passes between the Sun and Earth, a point on its orbit known as inferior conjunction. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

 

Venus Earth orbits

This simplified diagram removes the exaggeration inclination in the orbital planes of Venus and Earth. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

 

Elongated orbits transit of Venus

This diagram exaggerates the elongation (eccentricity) of Earth's orbit to illustrate why there is an asymmetry in the amount of time from one transit pair to the next. When ascending-node transits occur in early December, Earth is very close to perihelion, its closest point to the Sun in its elliptical orbit. Around this time, Earth is moving slightly faster than when it is near its farthest point from the Sun (aphelion) in early July. Due to Earth's different orbital velocities over a year, it takes 105.5 years to go from the second of two June transits to the first of two December transits, whereas it takes 121.5 years to go from the second of two December transits to the first of two June transits. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

Venus transit angles

This diagram shows the tracks of Venus across the Sun in 2004 and 2012, and how Earth just missed a transit in 1996 as Venus passed a little south of the Sun when it came to inferior conjunction. In 2020, Venus will be a little too far north of the Sun to transit its disk. For the upcoming transit, Venus will cross the Sun in the Sun's far northern hemisphere. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

Halley transit method

English astronomer Edmond Halley developed a brilliant idea for using transits of Venus to measure the scale of the solar system. Observers at different locations on Earth would measure slightly different path lengths for Venus as it transited the Sun by measuring the time it took Venus to go from second to third contact. Astronomers could thus triangulate the distance to Venus. From Kepler's laws of planetary motion, astronomers knew that Venus was 72.3 percent as far from the Sun on average as Earth, so by determining the distance to Venus, astronomers could easily calculate the Earth-Sun distance.
Courtesy Sky & Telescope

Venus Transit Angles

This illustration shows Venus's tracks across the Sun from 1388 to 2012. The top row shows December transits at Venus's ascending node and the bottom row shows June transits at Venus's descending node. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

Transits of Venus in the future

Starting in 3089 A.D., observers on Earth will only see one transit of Venus at the descending node. As this diagram shows, Venus will cross the Sun near its center in 3089, but it will just barely miss the Sun in 3081 and 3097. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

Venus transit timeline

This diagram shows past and future transits of Venus and how they occur in cycles lasting 243 years. Two transits occur 8 years apart, and then the next transit happens either 105.5 or 121.5 years later. The December transits occur when Venus is at its ascending node and the June transits happen at Venus's descending node. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

Long-term behavior of Venus transits

By plotting the number of days into each year when a transit of Venus occurs, it's easy to see the long-term behavior of transits of Venus, and the fact that we're fortunate to live during a period when we get to see two transits at both the ascending and descending nodes. Note the change from the Julian Calendar to the Gregorian Calendar around the year 1600. Retired NASA astronomer Fred Espenak provided S&T with the data for this diagram. (Click on the image for a high-res version.)
Courtesy Sky & Telescope

Long-term behavior of Venus transits

These diagrams show the long-term behavior of transits of Venus. During certain periods lasting centuries, both past and future, astronomers on Earth can only see one transit at an ascending or descending node. The diagrams also show how far north or south Venus crosses the Sun's disk at each transit. Adapted from Jean Meeus's book Mathematical Astronomy Morsels III, copyright 2004 Willmann-Bell, Inc. (Click on the image for a high-res version.)
Courtesy Sky & Telescope