Venus set for rare solar pass

This is the Sun and flying across the bottom - in ultra-fast motion - is Venus.

These images, from 2004, show one of the rarest astronomical events in our solar system.

It's the so-called transit of Venus.

SOUNDBITE) (English) DEAN PESNELL, PROJECT SCIENTIST, SOLAR DYNAMICS OBSERVATORY, NASA GODDARD SPACE CENTER) SAYING:

"Transits happen because a planet is between us and the sun and we go around the sun and you can think of us going around kind of flat. And the planets Venus and Mercury go around and they're tilted just a little bit. So when we can see them near the sun sometimes they're above the sun, sometimes they're below the sun and every once in a while they simply go across the sun."

Scientists here at NASA are gearing up for the solar pass, pointing a raft of instruments at the sun.

The phenomenon has been observed by scientists and skywatchers since the 1600s and has been used to make calculations about the size of the universe.

The transits happen in pairs eight years apart and the last one happened in 2004. But in between, they are separated by gaps of over 100 years.

The transit will happen on Monday and Tuesday, and it's expected to last just over six hours.

Andrew Raven, Reuters.