A simple guide to observing meteors

A simple guide to observing meteors

Observing meteors is one of the simplest and most instantly rewarding ways to enjoy astronomy, so here is some advice on how to view them. Often known as “shooting stars” or “falling stars”, they are fun for beginners to amateur astronomy because no equipment is needed to view nature’s own fireworks.

Perseid
A bright Perseid meteor. Image credit: Paul Sutherland

Meteors – commonly known as shooting stars or falling stars – are, of course, not stars at all. They are the streaks of light that appears when pieces of celestial debris enter the Earth’s atmosphere at speeds of up to 70 km (45 miles) per second and are vaporized.

But what appears as a bright flash is usually no bigger than a grain of sand, being destroyed and ionising the air around it at a height of between 80 km and 120 km (50- 75 miles). Sometimes it will produce a glowing train in its wake for several seconds.

Meteors are fragments of material ejected by comets orbiting within the Solar System. They can appear randomly at any time. But at various times in the year, the Earth’s orbit crosses the streams of dust left by different comets and around those times we see what are termed meteor showers.

Shower is something of an exaggerated term because, unlike showers of rain, you will rarely see more than one or two a minute at most. The number you see will depend not only on how much dust is entering the atmosphere but also on how dark your sky is and whether there is bright moonlight, for example.

Sometimes, larger chunks of comet debris blaze more brilliantly, producing so-called fireballs that rival Venus and sometimes even the Moon in brightness. However, they almost invariably are completely destroyed in their blaze of glory.

Technically, the particle itself is called a meteoroid and the streak in the sky is a meteor. Objects termed meteorites are stones that have survived a fall to Earth and are more likely to be linked to the asteroids.

Meteors can appear anywhere in the sky but shower members can be traced back to a radiant, in this case that for the Perseids

Meteors that cannot be linked to a shower are called sporadics. They can be told apart from members of a shower because the shower meteors will appear to radiate from a particular point in the sky. No matter in which part of the sky you see the meteor, you can trace back its path and it will cross that point. The meteors appear to have shorter paths the closer they appear to the radiant because they are heading more directly towards you.

The effect is one of perspective. The meteors are actually flying parallel to each other as they stream into the atmosphere but traced back, their paths converge on their radiant just as the parallel lanes of a long straight motorway appear to converge in the distance.

Different showers are usually named after the constellation in which the radiant appears to lie. So a strong shower that occurs every August and appears to radiate from the direction of Perseus is called the Perseid meteor shower, or simply the Perseids. Similarly a major December shower radiating from Gemini is known as the Geminids. Some shower names even specify a bright star close to their radiants such as the Delta (δ) Aquarids or Kappa (κ) Cygnids.

There are very rare occasions when observers do witness great numbers of meteors. They are called meteor storms and happen when the Earth passes through a dense clump of particles in the stream’s orbit. The Leonids generally reveal just a handful of meteors at maximum in November but many thousands an hour may be seen at intervals of around 33 years. The last spectacular display was in 1999.

Though storms are rare, it can be very rewarding to sit outside and watch the show when the Earth meets one of the regular reliable showers. You will need to be patient. Don’t expect just to glance upwards and see a meteor straight away. Instead prepare yourself for a watch of several minutes at least for the best chance of some results.

It is not only the sky brightness that affects the numbers of meteors seen during a shower. Many radiants don’t rise above the horizon until after midnight and the higher the radiant is in the sky, the more meteors will be seen. Also, as we get closer to dawn, the part of the Earth where the observer is situated is likely to be turning into the direction from which the meteors arrive. The combined speeds of the rotating Earth and the travelling meteor particle make any meteor travel faster and “burn” brighter.

The year’s main meteor showers

Shower When visible Date of

maximum
ZHR
Quadrantids Jan 01 – Jan 05 Jan 04 120
Lyrids Apr 16 – Apr 25 Apr 22 18
Eta-Aquariids Apr 19 – May 28 May 06 60
South.Delta-Aquarids Jul 12 – Aug 19 Jul 28 20
Perseids Jul 17 – Aug 24 Aug 13 80
Orionids Oct 02 – Nov 07 Oct 21 23
Southern Taurids Oct 01 – Nov 25 Nov 05 5
Northern Taurids Oct 01 – Nov 25 Nov 12 5
Leonids Nov 10 – Nov 23 Nov 18 15+
Puppid/Velids Dec 01 – Dec 15 Dec 07 10
Geminids Dec 07 – Dec 17 Dec 14 120
Ursids Dec 17 – Dec 26 Dec 23 10

What you need to observe meteors

Meteor observing is an ideal project for the starting-out stargazer because little more equipment is required than a garden chair to sit in and watch the sky. It is a fun activity to share with friends but it can also be of real scientific value if you make proper notes of your observations.

You will need a watch, a notebook, a red light and a pen or pencil. A voice recorder is especially useful as it will allow you to make your notes without taking your eyes off the sky. (Make sure the batteries are fully charged and keep a spare).

Find a spot well away from streetlights, sit for an hour or so at a time steadily watching a patch of sky, say halfway between the horizon and the zenith. There is no need to watch the radiant, in fact it is better to watch another part of the sky.

When a meteor appears, quickly note the time, estimate the meteor’s approximate brightness compared to the stars, their colour, relative speed (e.g. fast, medium or slow) and any particular features such as whether they left a train. Note too whether the meteor was a shower member or a sporadic.

You should also note the sky conditions such as the presence of any haze, cloud or moonlight and the brightness of the faintest stars you can see overhead, termed the limiting magnitude.

Your observations, properly made, can be very useful to major astronomical organisations and professional meteor scientists when combined with other members’ records. Try to follow the stricter guidelines of the International Meteor Organization if you wish to be a serious observer.

Do not expect to see the number of meteors quoted for any shower’s maximum rate. This is usually a figure that would apply in ideal conditions and with the shower’s radiant is directly overhead. It is called the Zenithal Hourly Rate or ZHR.

Top tips for observing meteors

1. Choose a night when a reliable meteor shower is at or near its peak activity and when you won’t be hampered by a bright Moon. These dates are generally well known in advance because professional astronomers, with the help of amateur observations, have managed to map the course of the streams of particles through the Solar System. (Serious observers will watch on any night to help gauge activity throughout the year but that is unlikely to inspire a beginner).

2. Find a location where the sky is not drowned out by the glare of streetlights. If a shaded spot in your garden can’t provide this, then perhaps a local common or a field out of town can be found. If you do observe away from home, make sure you are not trespassing, of course, and above all stay safe, by going with a couple of friends for example.

3. Make sure you are suitably dressed. Even during warm summers, it can get chilly at night, so you will be lucky to get away with T-shirts and shorts. Warm trousers, insulated boots, and a few layers on top such as a long-sleeved shirt and jumper plus possibly a fleece are advised for moderate vigils. You will need more in winter – such as your ski gear perhaps. Wear a cap or hood because much body heat is otherwise lost through the head.

4. Take a deck chair, camping bed or similar on which you can relax and watch the sky without straining your neck. You are more likely to keep at it like this – but make sure you don’t doze off! Some light snacks can help too, including a flask of tea or coffee. Alcohol will not help!

Related: How to photograph a meteor shower


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