Science

The moon will block out three planets in a rare lunar occultation

After Monday, this will not happen again for another 19 years.

The moon is going to eclipse several planets and a star on Monday, in a rather creepy-sounding astronomical phenomenon called an occultation.

Despite the sinister name, all it means is that the moon will pass across something else in the sky, blocking the view of it from Earth.

This one is particularly rare because the moon will slide across not one, but three planets within the space of 24 hours.

What is an occultation?

Occult GIFs - Find & Share on GIPHY

An occultation is any celestial event where an object in the solar system crosses in front of a further away planet or star. A classic example would be a solar eclipse, where the moon passes between the Earth and the sun.

When this happens, astronomers say the moon has eclipsed, or “occulted”, the sun.

And no, it has nothing to do with witches or the occult.

What’s going to happen?

Solar Eclipse 2017
A total eclipse of the sun

On September 18, the moon will cross Venus, Mars and Mercury in a 24-hour period.

As an added bonus, the moon will also shimmy across a star called Regulus, of the Leo constellation, which is one of the brightest in our sky.

According to EarthSky, the moon will not do this again until 2036.

The last time a triple planet moon occultation occurred was on March 5 2008, with Mercury, Venus and Neptune.

Can I watch it?

People stand with telescopes
Venus is the brightest planet in the line-up and will be visible from Australia (Owen Humphreys/PA)

The best place to see Venus disappear will be Down Under, according to the International Occultation Timing Association.

Our bright next-door neighbour planet may be visible in the daytime without a telescope from parts of Australia and New Zealand, and is the first to be occulted.

Regulus is next, and will best be seen from India and parts of the Middle East, while the red planet should be visible from parts of Mexico and Hawaii.

Mercury will be particularly hard to see since it is close to the horizon – plus you will have to be looking at the sky above the Pacific Ocean to catch a glimpse.

Why is this exciting?

Nasa GIFs - Find & Share on GIPHY

Occultations do not just provide stunning views – scientists can use them to suss out information on distant planets.

Astronomers only discovered Uranus had rings when it occulted a star in 1977.

Who knows what mysteries of space they will uncover this time?

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