The Transit of Venus
Facts about Venus transits, including when they occur and photos of the most recent events.
A transit of Venus occurs when the planet's body passes in front of the Sun from our viewpoint on Earth.
Only Venus and Mercury can behave in such a way. They are inferior planets, meaning their orbits lie within ours, and are the only planets that can pass between Earth and the Sun.
Venus and Mercury being inferior planets also causes them to appear to swing from one side of the Sun to the other in the sky, which gives rise to Venus’s popular names of the Morning Star and the Evening Star.
How often does a transit of Venus occur?
Some might think that we would see a transit of Venus on a regular basis, but this is not the case.
Venus’s orbit is tilted by 3.4° with respect to Earth’s, so most of the time when Venus comes between us and the Sun, from our viewpoint it passes well above or below the solar disc.
Observable transits of Venus only take place when specific conditions are met.
Venus has to be at inferior conjunction – the point that it’s closest to Earth and its disc is at its greatest angular size – and the orbital planes of both planets have to cross, which can only happen twice a year, in June and December.
Transits of Venus occur in pairs separated by eight years, but the gap between pairs is alternately 105.5 or 121.5 years.
When was the last Venus transit?
The last (or most recent) transit of Venus visible from Earth occurred on 6 June 2012. It was the second Venus transit of a pair, the first of which took place on 8 June 2004.
You’ll have to live a long time to see the next ones. The next transit of Venus occurs in December 2117, followed by another in December 2125.
What does a transit of Venus look like?
A transit of Venus appears as a relatively small black circle against our star.
The point at which Venus first touches the solar disc is called first contact, and marks the
beginning of the ingress phase.
Second contact occurs when the planet is fully on the disc, and marks the end of ingress.
Venus then crosses the face of the Sun in a matter of hours, after which it reaches the other side of the solar disc, marking third contact and the beginning of the egress phase.
Egress (and the transit) ends after fourth contact, when Venus’s trailing edge moves off the solar disc.
For a brief moment we are able to watch the clockwork motions of the planets as they journey around the Sun – and briefly glimpse the remarkable regularity of our Solar System.
We may not get to see another Venus transit in our lifetime, but there's still plenty observe when Venus is visible in the sky.
Below is a selection of images of the 2004 and 2012 Venus transits captured by BBC Sky at Night Magazine readers and astrophotographers.