The 2012 Transit of Venus: What it is and how to observe it

Tomorrow (Wednesday 6 June Australian time), Venus will transit or pass in front of the Sun for only the seventh time since the invention of the telescope. This extremely rare event occurs in a cycle that repeats every 243 years and if you miss the transit tomorrow, you will have to wait until December 2117 to have another opportunity to view it. The transit of Venus has both scientific significance (with early astronomers timing when it passed in front of the Sun in an attempt to measure the distance between the Earth and the Sun) and significant historical significance for Australia (the ‘discovery’ and mapping of the Eastern side of Australia by Captain Cook). Make sure you take a moment to observe the transit – be it through safe solar viewing methods, at a public viewing event or by webcast – as you won’t be alive to see the next one.

Safety warning! This article contains information on how to safely indirectly observe the transit of Venus using solar projection methods. If you are not familiar with indirectly observing the Sun, then I strongly suggest you don’t. Directly viewing the Sun will result in permanent eye damage and most likely permanent blindness. Watch the transit via webcast or at a public viewing event.

Anyway, rather than me try and create appropriate words about the significance of the Venus transit, why not watch the below fantastic short NASA video about this historical event.

 httpv://www.youtube.com/watch?v=ehHY9fTrb7Q

What will you see

For an observer in an ideal location, the transit of Venus will be a slow and graceful event. The exact start and finish time will vary slightly depending on your location but will start at approximately 8.16 am AEST and finish at approximately 2.44 pm AEST. All in all, you will have six and a half hours to watch as Venus slowly moves across the face of the Sun. For me, the most exciting time will be when Venus first begins to move in front of the Sun then when it moves away from the face of the Sun for the last time until 2117.

If you would like to know exactly what the transit will look like from your location (including event times), then I suggest you visit the http://www.sunaeon.com/venustransit/ website. The creator of this website has put together a fantasticprogram which automatically detects your location and plays a flash animation showing exactly what the transit will look like from your location

Venus Transit Event Times

There is very little difference for the start and end times for the transit for cities on the East coast of Australia. All times are in Australian Eastern Standard Time.

How to (indirectly) observe the 2012 Transit of Venus

If you don’t like the idea of only watching the transit on a webcast (which I don’t) and aren’t near a public viewing event and you have access to a cheap telescope or binoculars, then with the utmost caution, you may wish to use them to indirectly observe the transit. In astronomical jargon, indirect observing means that you use the binoculars or telescope to project an image of the Sun onto a white surface. Using this method will allow you to easily observe the black disc of Venus move across the face of the Sun.

A few words of caution. Do not leave your binocular or telescope unattended or in fact even relax for a moment. I have heard of more than one horror story where a small child has pushed an adults hand out of the way and looked through a pair of binoculars at the Sun directly before the adult has had the opportunity to stop them.

I have put together a Youtube video in which I talk about a variety of ways of safely indirectly observing the transit.

httpv://www.youtube.com/watch?v=eVi6rHQ-RLg

Live 2012 Venus Transit webcasts

If you aren’t familiar with safe indirect solar observing techniques or have cloudy weather forecast (which I do), don’t despair as there are plenty of other options for watching the transit.

Probably the ‘coolest’ of the webcast options is to see the transit as it is observed live by a variety of satellites whose job it is to monitor the Sun. My web searching turned up one surprise for me. The NASA/ESA SOHO satellite will miss seeing the transit due to the manner in which it orbits the Earth. At this stage, the only Sun watching satellite that I know of that will see the transit is NASA’s Solar Dynamics Observatory.

• NASA’s Solar Dynamics Observatory 2012 Venus Transit page

A more ‘down to Earth’ option will be watching a webcast from one of the many observatories that will be webcasting the transit live. Broadcast times will very depending on where the observatory is located on the Earth’s surface. I suggest you try a couple of the links between 8.16 am AEST and 2.44 pm AEST and see which one is live.

• NASA list of live transit webcasts
• http://events.slooh.com/
• http://www.ccssc.org/transit2012.html
• http://www.sydneyobservatory.com.au/watch-a-live-stream-of-the-transit-of-venus/
• http://live.parssky.com/
• http://uocmas.info/
• http://tinyurl.com/7lowf83

You may be wondering why it will be 105 years until the next transit. The answer is twofold. Firstly, Earth and Venus orbit the Sun at different speeds (Venus at 35.02 km per second and the Earth at 29.8 km per second). The end result of this is that Venus and the Earth are in a direct line with the Sun every 584 days (an event known as a conjunction). In theory, this then means that a Venus transit could then happen every 584 days. However, a second factor comes into play. Venus’s orbit is tilted 3 degrees relative to the Earth’s orbit around the Sun. This means that most of the time, when Venus and Earth are in that direct line (of sorts) with the Sun, that Venus is either below or above the Sun as seen from the Earth.  The end result is that transits occur in a pattern that repeats every 243 years with pairs of transits every eight years separated by gaps of 121.5 years and 105.5 years.

Make your own Venus Transit flipbook

Finally, you may want to make your own souvenir of the Venus transit. I have made an old fashioned Venus Transit flip book which individuals are free to download and use.