Page 86 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

SOLAR ECLIPSES

THE ANCIENT CHINESE THOUGHT SOLAR ECLIPSES
WERE THE SUN BEING EATEN BY A DRAGON. TODAY
WE KNOW EXACTLY WHAT CAUSES THEM – AND
WHERE TO GET THE BEST VIEWS

One of the most breathtaking won’t be visible from the UK, is around 400 times further
astronomical events you can though, so you’ll have to travel away. As a result, the two
witness is a total eclipse of if you want to see it. objects can appear to be
the Sun, also known as a total On Earth we’re really rather the same size.
solar eclipse. Not only is it an lucky that the Moon is just the However, we don’t get
experience you’ll never forget, right size and orbits at just the a total solar eclipse every
but it also shows the Solar right distance to make total time the Moon moves
System in motion through the solar eclipses possible. You between Earth and the
fortunate alignment of three may wonder how they happen Sun. The lunar orbit
astronomical bodies. at all since the Sun is so much is tilted, so that
The fi rst object is our planet, bigger than the Moon. Well, it sometimes
the Earth, which slowly orbits due to one of the most amazing
the second object, the Sun. The coincidences in nature, even
third object in the equation is though the Moon is 400 times
the Moon. We get an eclipse smaller than the Sun, the Sun
when the Sun, Moon and Earth
are temporarily aligned.
DAVID NUNUK/SCIENCE PHOTO LIBRARY, DETLEV VAN RAVENSWAAY/SCIENCE PHOTO LIBRARY, JOHN CHUMACK/SCIENCE PHOTO LIBRARY,
The next total eclipse takes
place this year on 13 November,
but totality will only be seen
from Cairns, Australia. It will,
however, be seen as a partial
eclipse in central Chile, and
areas of New Zealand, such as
Auckland and Christchurch. It

CASTING

SHADOWS Umbra
DAVID PARKER/SCIENCE PHOTO LIBRARY, PETE LAWRENCE, LUC VIATOUR During a total solar eclipse, if you’re in the ‘umbra’ Penumbra
See total coverage of the
Sun in the umbra

you’ll see the entire Sun being slowly covered by the
Moon and get the full glory of totality. There’s also an
area around the umbra called the ‘penumbra’, where
the shadow isn’t quite so dark. On the ground this forms
a large circular zone where you see more and more
of the Sun the further you get from the umbra until you
don’t see an eclipse at all. So whenever people in one
location see a total eclipse, those in a large surrounding
area will see a partial eclipse. There are a maximum of
fi ve solar eclipses in any given year.
Sun creates an umbra and penumbra on Earth
86 skyatnightmagazine.com 2012 The cone-shaped shadow of the Moon cast by the