Rev 3. 11/08/08
This is a basic guide aiming primarily to assist in identification of meteors, comets and other natural stellar objects as distinct from
Unidentified guided or piloted craft.
What is a Meteor
The Royal Astronomical Society has proposed a new definition where a meteoroid is between 100 µm and 10 m across. The NEO definition includes
larger objects, up to 50 m in diameter, in this category.
Objects lighter than a meteor are deemed an asteroid. Smaller is interplanetary dust.
The methods used to distinguish are
Characteristics and Flight Path:
07/ Apparent altitude
09/ Other behavior
10/ OK, so I saw something, and I've been through this guide - what now?
11/ Meteor activity throughout the year, storms, outbursts, and future predictions
12/ A little ramble from me on Meteors
Characteristics and Flight Path:
1/ Did the object fly straight, without making any turns or changing it's apparent velocity?
If you can answer "yes" then the object may
well be a meteor... although some experienced observers have on very rare occasions seen meteors that appear to slowly curve, or to wiggle mildly,
this is related to the composition of the object, its irregularity and the flight path as it passes though denser parts of the atmosphere.
How fast was the object?
Most meteors are fast and can cross the sky from almost horizon-to-horizon in under 10 seconds. The vast majority last less than a second. At the
other end of the spectrum, and very close to the upper speed limit of orbiting man made satellites, are slow meteors.
The slowest meteors can cross most of the sky in about 45-50 seconds, but it's exceptionally rare to see one last that long.
If the brightness of the object changed relatively slowly (or hardly at all), and the object appeared to be white, it may well have been a satellite
if it was visible for such a long time. Keep in mind that satellites are only visible for a short while after sunset/before dawn at this time of year
since the sun is well below the horizon. During Summer, satellites are visible most of the night since the sun is never really very low below the
horizon. You can often work out if what you saw was a satellite by checking Satellite tracking
There are also occasional super-speed meteors that originate from outside our solar system. When you see one, the motion of the meteor is often hard
to see - it's as if a line just appears out of nowhere in the sky, and disappears as fast as it appeared. These usually last only a fraction of a
second, and are often dim, although bright super-speed meteors are possible too. Since brightness increases with size, and since larger meteoroids
with high velocities are more prone to catastrophic failure of structural integrity due to the more intense forces involved during the initial phase
of entry, it's likely that if you see one of these, that it will disintegrate in a bright flash of light at the end of its path. This may explain at
least some of the "flash in the sky" UFOs that have been reported in recent months here.
The same is also true of meteoroids originating from within our own solar system, even though the upper speed limit is much lower, they may also
disintegrate in a bright flash or "terminal burst".
Meteors can be almost any color, although many appear to be white. Common colors seen include: Yellow, Green, Orange, Red, and Blue. Gold and Bronze
are also quite common. The brighter the meteor the more chance of seeing color, and it's not unusual to see more than one color in the same
Meteors range in brightness from imperceptible by the naked human eye to being as bright as the sun in some exceptional cases. It's a common
misconception that bright meteors are rare - they are not, although exceptionally bright meteors are uncommon. On any given night there is a fair
chance of seeing a fireball (brighter than Venus which is -4 magnitude) class meteor or two. If you watch meteors a lot you stand a good chance of
seeing meteors around the brightness of the moon.
Given the unusually high activity at the time of writing, bright meteors are even more abundant. Numerous reports attributable to this high activity
have been submitted to ATS and other sites/organizations. See below for links to some of the observations posted here on ATS.
The table above shows the brightness of various celestial objects that can help when trying to estimate the brightness of an object you saw. Please
note that negative values are brighter than positive values, and that each increment represents 2.5x. So, a 3rd magnitude (+3 mag.) star is 2.5 times
than a 2nd magnitude (+2 mag.) star.
Meteors can appear to be "balls" or "spheres" of light, which is usually associated with slower meteors, but they can also have a tail, making
them appear to have a "tear drop" shape (generally faster meteors). A tail or wake will last no longer than a second before fading away, but meteors
can also produce much longer lived "Persistent trains", as they are known, which can last for 10's of minutes in extreme cases.
To a meteor, there is no up or down. Meteors can appear to shoot up from the horizon (Earth grazers) or drop directly down, as well as every other
angle in between! If two people separated by a few hundred miles see the same meteor, they will see it fly in completely different directions - one
might see it fly up, and the other down. This is possible since we live on a curved surface.
Direction also affects apparent speed - just as a train heading directly towards you will appear to stand still if you see it from some distance, when
a fast meteoroid hits the atmosphere it will not appear to move if it heads directly towards you. This is quite rare to see, though - more often the
meteor will be just off straight, and will appear to move extremely slowly in the sky for the duration of its short life. See below for example
7/ Apparent altitude
People will often insist that they saw a meteor land just over the hill, or that it flew only a few hundred feet over head, but in most cases this is
physically impossible. In simple terms, it's an optical illusion. Our brains are particularly bad at judging distance and altitude especially when it
comes to unfamiliar objects in the sky. See this link for a full explanation:
Meteors can fool our eyes
While the object in question may have looked very close and bright, most meteors are burn up from 100 to 60 miles high. Rare indeed is the meteor that
makes it down to even the 20 mile high point, and on the rare occasions this does happen, the would be meteorite completes this last phase (known as
the "dark flight" phase) of it's journey at free-fall speed, and unseen since it's too slow to produce any light. The only exception to this rule
is if the meteor is made of very dense strong material, and is large enough to keep a significant portion of it's cosmic velocity - an asteroid the
size of a small car for example. If you saw one of these, you'd know about it... if you were far enough away to survive!
Some people also mistakenly assume that if is not high above the horizon it can not be a meteor, but this is not true - as long as the object stays
above the horizon, and is not seen passing in front of obstructions on the horizon, there is no reason why it could not be a meteor.
In rare cases, meteor can produce sounds. These fall into two categories. Sounds heard at the same time as the meteor is visible, often described as a
"sizzling" type sound are known as "electrophonic" sounds. Sometimes even dim meteors can produce these sounds. Then there is the possibility of
sonic-booms being produced if the meteor is large enough, and penetrates deep into the atmosphere. These would usually be heard 2 or 3 minutes after
seeing a bright meteor.
9/ Other behavior
If you are lucky you can see meteors that appear to:
*Sparkle, or trail sparks
*Split or fragment into two or more pieces
*Flare violently along their path
*Explode in a terminal flash of light
*Fade in and out along their path, sometimes remaining invisible for short periods of time
*Come in simultaneous pairs or more
There may well be others that I'm forgetting of have never seen/heard of. Meteors can still surprise even experienced observers with odd and unusual
behavior. I'd encourage anyone seeing (or hearing) a very bright meteor (equal to or above the brightness of the moon) or seeing any unusual behavior
not listed here to report it to one of the organizations that can be found in the links that I have listed in the
Taurid Swarm year thread
End of Part 1
10/ OK, so I saw something, and I've been through this guide - what now?
If this guide has done it's job, then the chances are you have identified what you saw. If you are still unsure, check the links below for other
guides, info and examples, and if you still think you have a UFO, then by all means post a new topic after having done a search to see that there is
not already a pre-existing topic relating to what you saw.
If you think what you saw was an unusual astronomical phenomenon, then head over to the Space
forum and tell us about it - we would love to hear your account! All observations are useful including those of misidentified
objects, if only because other people will be able to learn from the mistakes of others.
11/ Meteor activity throughout the year, storms,
outbursts, and future predictions
I think it's fair to say that in general, most people apart from a few amateur astronomers, meteor observers, and keen sky watchers are not aware of
just how much material finds its way to Earth's atmosphere. Although we think of space as empty, it's not really, and Earth's orbit takes us
through space that has in the past been crisscrossed by the dusty debris trails left by many comets and asteroids (to a much lesser degree). A good
analogy would be the sky in an area surrounding a busy airport (The Sun), on a day when it's full of contrails.
During any given year, there is a background of activity that never ceases, although at certain times of the year the activity is higher. It's when
we intersect the orbit of a comet that has been through that particular part of space in the relatively recent past that we get a meteor shower, or if
we are lucky, and our orbit takes us through the heart of the dust trail left by the comet soon after the comet produced that trail, a meteor storm
can be expected.
See this FAQ for more info on this subject: Meteor FAQ
Although this is not common, it does happen, and more often than most people realize! In the last 10 years alone there have been at least three
confirmed storms (if the "ZHR" or "hourly rate under ideal conditions" > 1000), and at least twice this number of confirmed outbursts (when the
rate is significantly higher than in a normal/average year).
Not only that, but this year, as I mentioned at the start of this post, has seen significantly above normal activity! We started the year off with a
outburst in January, followed by an Eta-Aquarid
outburst in May that was
twice as strong as most years, followed by strong outbursts from the Perseids
in August and the Orionids
which is still going now,
though it's back down to more or less normal.
We can expect more high activity this year too. The Taurids
(which are also expected to be in outburst mode in 2008 - see links below) will be
peaking over the next week or so, and by the time they start to wind down the Leonids
will be active, and we are could see a strong outburst
(ZHR up to 150) at 0:22 UT on the 17th November according to predictions by
. Not everyone will get to see the peak although there should still be at least some enhanced activity for those with clear skies
before and after the time of the peak.
Although this year (2008) has been busy, "freak" years like this are bound to come along once in a while, and perhaps we are only seeing the tip of
the iceberg - there are numerous accounts from the past of strong meteor activity. The Chinese in particular kept detailed records over hundreds of
years, and there are many accounts of "stars falling like rain from the heavens". Perhaps, just like sunspots, there are fairly regular long term
cycles of maxima and minima, and it's just speculation, but we could be heading for a meteor maxima.
To really put things into perspective, new comets and asteroids are being discovered all the time, so sooner or later we will plough directly into the
very core of a newly laid trail of dust. Don't be surprised if that happens sooner rather than later!
We are living in exciting times, and for the first time in recorded history we have the almost godlike ability to predict to within a handful of
minutes, the time at which Earth will pass through the most meteoroid rich part of a dust trail that is hundreds of years old. Every year the
technology improves, and the models used to simulate dust trails are tweaked, so predictions become even more reliable.
12/ A little ramble
from me on Meteors
Our computer models are a great tool, but they would be useless were it not for astronomers around the world who contribute observations on comets and
meteor showers, and most of these astronomers are amateurs - ordinary people just like you and me. Anyone can do it once they learn a few simple
rules, and the basics of finding your way around the stars. Why not give it a try yourself? Not only will you help to improve our ability to predict
future meteor showers, but you may also see some of the most spectacular fireworks nature has to offer, and Natures fireworks are more than capable of
making even our artificial displays seem like damp squibs in comparison!
Read some accounts about the outburst that first got me interested in meteors here:
I remember turning on the TV, after having stayed up the whole night watching meteors exploding all over the sky, and chuckling to myself when the
newsreader announced that UFO reports had been coming in since the early hours.
It's fitting that in a little under 3 weeks time will be the 10 year anniversary of this event (also marking a decade of interest in the subject for
), and perhaps if we are very lucky we might just see a repeat performance!
UFO or meteor?
Meteor shower calender
Another meteor shower calender
Heads up - it's a Taurid Swarm year!
Falling stars..I just saw two
weird green ball with tail
General information vabout meteors
Organizations and mailing lists:
International Meteor Organization
International Meteor Organization
Meteor Observing Mailing List
[edit on 11/8/2008 by Badge01]
Mod Edit: All Caps – Please Review This Link.
[edit on 11/22/2008 by Gools]