30 BBC Sky at Night Magazine August 2021
If you get into watching the
Perseids this month, why
not keep a methodical record
of the meteors you see over
each hour. This will make an
interesting keep-sake of a
successful night of observing
and can aid scientists with
their work too. Records of
visual meteor observations
are still used today by
researchers as a way to
gather information about
the meteoroid streams left
by comets and asteroids.
Pictures, video and
eyewitness reports can also
be a key source of useful data,
particularly when it comes
to bright meteors known
as fireballs, as these cansometimes drop meteorites
to the ground.
As these started life as
fragments of other bodies
in the Solar System, such as
asteroids, this material can be
of scientific importance and
there are teams worldwide
who try to recover it with the
help of footage and sightings
from the public, as well as
dedicated camera networks.
To find out more about
contributing to such ‘citizen-
science’ projects, look at the
websites of the International
Meteor Organisation (www.
imo.net), UK Meteor Network
(https://ukmeteornetwork.
co.uk) and the UK Fireball
WIL Alliance (www.ukfall.org.uk).
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the Perseid
meteor shower
the process. The narrow ribbon of light that occurs
when this happens is the meteor – what many call a
‘shooting star’ – and they’re happening all the time.
On a clear night if you look up at the stars for, say,
half an hour or so, it’s highly likely that you’ll see a
meteor at some point – especially from an observing
site with dark skies. Many meteors that you see
like this will be what’s known as ‘sporadic’ meteors;
essentially that means that they are random in
nature and can appear anywhere in the sky, going
in any direction. What’s different with the Perseid
meteor shower this month is that Perseids, while they
can materialise anywhere against the backdrop of
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point on the sky – astronomers call it the ‘radiant’.A trick of perspective
This behaviour is, in fact, an optical illusion. The
meteors are actually travelling on broadly parallel
paths, as the meteoroids that create them plough
into the top of Earth’s atmosphere. It’s merely a trick
of perspective that makes them look like they’re
zooming across the sky from the radiant point.
While ‘normal’ sporadic meteors originate from
meteoroids scattered in a fairly random way between
the planets, meteors in meteor showers like the
Perseids occur when Earth passes through a streamof dusty material left by a comet or asteroid as it has
journeyed around the Sun. In the case of the Perseids,
that’s a cloud of dust left by Comet 109P/Swift-Tuttle.
Every year Earth’s orbit brings our planet into a
position where its path intersects with that trail; wePlay a part in gathering valuable scientific data for meteor research
Recording your observations
Þ The UK Meteor Network keeps an archive of its meteor
detections; this ground map shows its record for 2017’s meteorsA bright Perseid is captured as it
streaks across the night sky
over Exmoor in August 2016>Ye l l ow : length and direction of
each meteor; Green: bearing lines
of the beginning and ends of meteor
trails as seen from different stations