Once in a century lunar eclipse
THIS weekend stargazers will be treated to a once in a lifetime lunar eclipse event - but you'll have to get up early.
Early Saturday morning, the night sky will feature a rare blood moon lunar eclipse and it will be the longest such event in roughly a century. Even better news, Australians are expected to be among those with the best view of the slow-moving astronomy event.
The moon will be low on our horizon when it starts to go dark and it will set while completely immersed in a dull-red stain.
A lunar eclipse occurs when the Earth moves between the sun and the moon, completely blocking direct sunlight from reaching the moon, which gives the moon an orange/red hue that earns it the moniker of a "blood moon".
But why does the moon turn red?
Instead of going dark, the way the sunlight refracts around the Earth gives the moon a red colour as some of the sunlight entering Earth's atmosphere, notably the red spectrum, is scattered in a way that gently illuminates the moon behind.
However the brightness of the red colour depends on how dirty the atmosphere is due to volcanic eruptions - and experts don't believe this particular blood moon will display a strong red.
However the one hour 43 minute duration of the eclipse is just four minutes off the maximum possible length, according to NASA. And there won't be another one viewable from Australia until 2021. So if you enjoy astronomy, it's definitely worth getting up for.
The event will kick off at about 3.15am (AEST) on Saturday, July 28. The moon will start to turn red from about 5.30am.
Across Australia everyone will see the moon enter Earth's shadow at the exact same moment but those in Western Australia are the only ones who will be able to watch the entirety of the eclipse.
Lunar eclipses generally last much longer than their solar counterpart. The shadow cast by the moon is much smaller than that produced by our own planet.
The outcome is generally that a solar eclipse is only seen by a relative few who fall beneath the moon's masking orb. But the night-time transformation of the moon into a bloody-red orb can be seen by anyone on the Earth below while it is night.
On Saturday morning, the moon will be at apogee - the furthest point in its orbit from the Earth. This means it will be passing through space at a point where the cone of Earth's shadow is wider, making the eclipse last longer.