Venus – Diving to the Sun

Seth Jarvis

With all the excitement surrounding the May 20th Annular Eclipse, it’s easy to overlook something else that’s astronomically very interesting in the night sky.

Venus is dominating the western skyline after sunset these days, and the only thing brighter in the night sky is the Moon.

We just experienced our “Super” Full Moon on May 6th, and the Moon is now headed for an important appointment with the Sun on May 20th.  (You do have your eclipse viewing equipment ready, right?)

Venus, too, is plodding through space towards its own astronomically significant rendezvous with the Sun.

Right now Venus is high in the west at sunset, and a little casual observation will reveal that Venus is sinking a bit lower towards the horizon each night.

Because Venus is closer to the Sun than we are, it orbits the Sun faster than we do.  Venus’ average speed around the Sun is 72,000 miles per hour, while we poke along at a more leisurely 67,000 mph.

Venus is on the inside lane of our solar system racetrack, and it’s going faster than us.  It may be behind us now, but it’s coming up fast and getting ready to pass.

Today, May 7th, Venus is 37 million miles from Earth.  But in three weeks, on May 28th, it’ll be only 27.7 million miles from us.

Here’s the way it would look if you could fly a few hundred million miles above the Sun and look back down at the inner solar system:

From now until Venus is too close to the Sun to observe, you can use a telescope to study a phenomenon that was hugely important to science.  Four centuries ago Galileo turned his telescope towards Venus and observed that night after night Venus changed its size and showed phases, just like the Moon.  The size changes were due to the changing distances between Earth and Venus, and the phases were caused by the changing angle of sunlight between Earth and Venus.

There could be only one explanation for this. Earth was not the center of the solar system; the Sun was. Copernicus had it figured out, but Galileo had found the physical proof.

This is Galileo's sketch of Venus changing size and phase during several weeks of observation.

With a modest telescope operating at 40 power or better, a look at Venus during the next three weeks will reveal Venus changing in size and phase, just as Galileo saw it.

What’s really cool is that when Venus disappears into the glare of the Sun around the first of June, you only need to wait a few days until June 5th and then you can use the same eclipse glasses and telescope/binocular filters that you got for the eclipse on May 20th to observe a rare (next one visible to us will be in 2125) passage of Venus directly across the face of the Sun.  That super-bright planet you see in the west tonight will become a small black dot on the Sun in a few short weeks.

And if you plan to watch it again, you’d better start your intensive program of clean living, healthy foods, exercise, and get your sleep every night, because the next transit of Venus visible from anywhere in the world won’t be until the year 2117, and the next transit visible from the western hemisphere won’t be until 2125.

Happy viewing!

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2 thoughts on “Venus – Diving to the Sun

  1. Sam’s club in Murray at the WEST edge of their parking lot. Volunteers from Salt Lake Astronomical Society will be there.

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