The Half-Astrophysicist Blog

Venus Passes Through Inferior Cojnunction

Venus passes between the Earth and the Sun tomorrow, October 29th.  We usually don’t see this phenomena as Venus is up during the day.  However, Venus does not pass directly between the Earth and Sun.  From our perspective, it passes slightly below the Sun.  The Solar and Heliospheric Observatory (SOHO) has a camera with a coronagragph (a little disk the blocks the Sun) and gives us a nice view.  Here is a pic from today.

Venus is the bright guy at the bottom.  The streak is due to the fact that Venus is so bright, it bleeds over into neighboring pixels.

Now the main reason I mention this is that next time Venus undergoes inferior conjunction, it will pass directly between the Earth and the Sun.  This is called a transit and will happen on June 5th/6th 2010 2012 (and I am telling you now, so no crazy people get to say in 2012 that no one predicted this before!)  With proper solar filters or a solar telescope, you can see the disk of Venus on the face of the Sun. For most of North America, the transit will be in progress at Sunset (you can find more info about what you can see from your location here).  We will see the first part but not the entire transit.  The last time this happened was in 2004 and the transit was in progress at Sunrise.  If you put the two together, I will have seen a whole transit!

Mark you calendars, because these are much more rare than you think.  They occur in pairs separated by 8 years.  After the 2012 transit, you have to wait until 2117 for the next one!


October 29, 2010 - Posted by | Astronomy, Observing, Solar System


  1. I guess you mean “June 5th/6th 2012” in the second paragraph ?

    Comment by Song Huang | October 29, 2010 | Reply

  2. D’oh! Thanks for the catch.

    Comment by halfastro | October 29, 2010 | Reply

  3. At 6am in Medjugorje, Bosnia Hergovina we saw a very large ring around the moon but it did not come out on my camera but many people saw it. Any explanations please?

    Comment by John Goldingham | November 1, 2010 | Reply

    • Most rings are due to ice crystals in the atmosphere. Given you latitude and the time of year, this is very plausible. Although beautiful, they can be difficult to photograph. If your camera was on automatic settings, it probably took exposure and auto white balance settings for the sky, not the ring around the Moon. Frequently the ring will end up underexposed and not show up (if it is overexposed, you will see the ring, but it won’t look nice!)

      Comment by halfastro | November 3, 2010 | Reply

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: