Total eclipse – blink and you may miss it

The April 20, total solar eclipse is a unique astronomical event, but it’s not as rare as you may think.

A total solar eclipse occurs about once every 18 months, but each eclipse can only be seen from a small part of the Earth.

“Total solar eclipses are [only] visible from a given location on the Earth every 300 to 400 years,” says Professor Steven Tingay from the Curtin Institute of Radio Astronomy at Curtin University in Western Australia. 

With more than two-thirds of the Earth covered by ocean, many total solar eclipses are not witnessed, which is why many people think of them as rare.

Those observing the eclipse from the North West Cape peninsula in Western Australia will still earn some bragging rights, however, as Thursday’s eclipse is a special type, known as a “hybrid eclipse.”

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“It begins over the Indian Ocean as an annular eclipse, where the Moon is slightly too small to completely block the Sun and a ring of sunlight shines out from around the dark Moon,” says Dr Tanya Hill, Senior Curator of Astronomy at the Melbourne Planetarium.

“By the time the Moon’s shadow reaches land, it will become a total eclipse – the Moon now appears large enough to completely block the Sun, and it is the Moon’s umbral shadow that falls on Earth.”

Totality will occur at 11:30am local time (1:30pm AEST, 3:30am UTC) and last for 58 seconds. 

Dr Kat Ross from the International Centre for Radio Astronomy Research at Curtin University says that the world class dark skies in Western Australia make it the perfect place to observe the Universe and to host world class, state of the art telescopes.

“The vast, dry, flat landscapes of the Murchison regions is host to Inyarrimanha Ilgari Bundara, or the Murchison Radio Astronomy Observatory (MRAO). This observatory site is so removed from the technology of cities, astronomers can detect the quiet radio light from our Universe, studying things from the first stars of the Universe, to the remnant bubbles of gas left after the death of a star.”

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While those located in the north and the west of the country will experience the best show, the effect will be felt nation-wide, with a partial eclipse visible across most of the continent.

The April 20 eclipse is the first of five which will be visible in Australia over the next 15 years, but as Professor John Lattanzio of the Astronomical Society of Australia explains, it’s not something we should take for granted.

“A total solar eclipse … requires the moon to totally cover the Sun. But the moon is moving away from us and so we will only have eclipses for another 600 million years.

“Best to look at them now, while you have the chance!”