Shooting Stars

August is a great time for seeing shooting stars.

The Perseid meteor shower peaks near the middle of the month.

Warm nights welcome one of the best meteor displays of the year.

Astromagazine has a 1 minute Youtube video of the Perseids.

Click here to see it.

Meteors

Meteors, shooting stars, are caused by small grains of space dust, meteoroids.

When high speed meteoroids enter the atmosphere, they can be seen as shooting stars.

It is often said the the dust ‘burns up’ in the atmosphere.

That’s not quite true, it’s just a shorthand way of explaing what happens.

The dust particle enters the atmosphere with lots of movement energy.

This energy strips electrons from gas atoms in our air.

The gas atoms are ionised and begin to glow.

As the particle burrows deeper into the air, it forms a thin tube of ionised gas.

That glowing tube follows the dust grain as a meteor.

It looks like a falling star.

Speed and height

Meteors typically collide with our atmosphere at around 70,000 km/hour (50,000 mph).

The streak of light, the shooting star, appears about 100 km (60 miles) high.

A meteor seen from space: Ron Garrard, NASA, International Space Station

Colours

Meteors aften show distinct colours.

The colours come from elements in the meteoroid and in the air.

Here are some colours and their connected elements:

Yellow = iron

Yellow-orange = sodium

Green = magnesium

Red = atmospheric oxygen & nitrogen

Meteor Trains

The ionised glow from a bright meteor can last for a while after the meteor has passed.

This glow is a meteor train. The trains can last from a few seconds to several minutes.

The Perseids are known for bright meteors.

Some will leave distinct trains.

A Youtube video from NASA shows that the Perseids are the best display for bright meteors, fireballs.

Click here to watch the video.

Meteor Showers

A meteor shower happens when a concentrated trail of dust hits the atmosphere.

This trail is usually left in the wake of a comet that has passed the Sun.

So meteor showers come from comet dust.

The Perseids

Origin

The Perseid meteors come from Comet Swift-Tuttle.

Swift-Tuttle has a 133-year orbit around the Sun.

It last appeared in our skies in 1992.

Perseid radiant: NASA/JPL

The meteoroid trail hits our atmosphere in the direction of the constellation Perseus.

So the display is the Perseids.

The point in the sky from which they appear is called the radiant.

You can trace the Perseids in our NASA/JPL time-lapse image back to the the radiant.

Dates and times

The all important information. When can I see the Perseids?

They actually cross our skies from late July to late August.

On most nights, their number is small.

But on the peak nights, the display can bring around 30 meteors an hour.

This year the peak night is August 12th to 13th.

The Perseids are visible all night, from sunset on the 12th to sunrise on the 13th.

The best time to look is after midnight, when we may see up to one every minute.

This year, 2024, the Moon is at half phase so its light will not interfere with a meteor watch.

Meteor watch

It’s best to choose a dark spot for observing the meteors.

Try to find somewhere free from the direct glare of street lights.

Wrap up warm, it can get cold even on a summer night.

Take a snack and flask with a hot drink. You may be out some time!

Make yourself comfortable on a sun-lounger.

Then look up at the sky!

The meteors will scatter across the sky so looking in any direction works.

I wish you clear skies in August to see those falling stars, the Perseids.

The author: Dennis Ashton is a Fellow of the Royal Astronomical Society and a Wonderdome presenter.

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