Page 81 - All About Space 68 - 2017 UK

The Great American Eclipse
The Great American Eclipse

A How a solar eclipse is made
total solar eclipse offers the most
captivating and fleeting astronomical
sight of all: the solar corona. Invisible
at all other times because of the glare
its way it casts a two-part shadow on the Earth
of the Sun's disk, this outer atmosphere is only The Sun is a disc, so when the Moon occasionally gets in
revealed to onlookers for a couple of minutes in
the middle of a total solar eclipse, when the Moon Identical apparent size Umbral shadow
blocks 100 per cent of the Sun's light. This will The Sun is 400 times larger The narrow inner core of
happen in some parts of the USA on August 21, 2017. than the Moon, but also 400 the Moon's shadow causes a
times farther away. blackout that allows eclipse
A total eclipse of the Sun can only happen at New chasers to see the solar corona
Moon, when the Moon is precisely between the
for a few minutes.
Sun and the Earth. It doesn't happen every month,
because the Moon's orbit is inclined by 5 degrees The path of totality
relative to the Sun's apparent path through the The umbral shadow is
sky (which astronomers call the ecliptic). So most
about 112.6km (70 miles)
months, the two bodies miss each other. However, wide, but those near its
about once every 18 months or so, the New Moon centre-line experience
crosses the ecliptic and gets precisely between the totality for the longest.
Sun and Earth.
Thanks to the Sun and Moon being of almost New Moon Penumbral shadow
identical apparent size in our sky, our small satellite A solar eclipse occurs When Earth passes through the
can block up to 100 per cent of our star's light, but every 18 months or so Moon's fuzzy shadow, most
only as seen from within when a New Moon crosses people see only a partial eclipse.
the ecliptic.
the Moon's darkest
'umbral' shadow.

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