A meteoroid that survives passing through the atmosphere without disintegrating is then called a “meteorite.”  Most meteoroids do not survive their journey through the Earth’s atmosphere and disintegrate into very small particles.  It is estimated that each day the Earth gains over a thousand ton of mass from the fall of tiny meteorites.

When can meteors be seen?

Every day millions of small particles enter the Earth’s atmosphere and cause meteors.  Most meteors are so brief or small that they go unnoticed.  Most meteors can only be seen at night, although some a bright enough to be visible during the day.  Small meteors, as small as pebbles, might appear for a second or two before disappearing, while larger ones stay visible longer and sometimes appear brighter as they burn up while disintegrating.  A very bright meteor is called a fireball.

A meteor’s altitude is usually within the 75 to 100 kilometer range in the atmosphere, or the Earth’s mesosphere.  A meteor is visible to an observer around 65-120 kilometers above the Earth’s surface.

What creates a meteor?

The bright light that is a meteor is the result of heat produced by a meteoroid’s entry into the atmosphere.  The ram pressure, or pressure exerted by the meteoroid moving at high velocities through the atmosphere, generates heat.  This pressure then heats the meteorite and the air molecules around it.  The surface of the meteoroid reaches high enough temperatures to vaporize some of the atoms and molecules on it as well as atmospheric gases around the meteoroid.  These heated, ionized particles form the trail of glowing vapors that we see as a meteor.   Meteors appear very briefly because the vaporized gases in the bright streak cool and disperse rather quickly.

Where do meteoroids come from?

The use of “meteor” to refer to the actual cosmic rocks is actually incorrect and not technical; these celestial objects are actually meteoroids.  Where do meteoroids come from?  A scientist would tell you they come from asteroids, or some come from comets, and some from the Moon or Mars.

What are meteor showers?

Though millions pass through the Earth each day, throughout the year an unusually large amount of meteors may occur at the same time.  This occurrence is known as a meteor shower.  Meteor showers sometimes occur when the Earth passes through remnants of a comet that passed through while orbiting the Sun.

What are meteors made of?

Meteors are made of vaporized and ionized gas trails of meteoroids.  Meteoroids and meteorites are made of minerals rich in various compositions of silicon, sodium, copper, potassium, iron, and nickel.

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The meteorite has gained its fame from one of the world’s best-loved superheroes, Superman. The Man of Steel’s Achilles’ heel is the mineral kryptonite – and the villains in his life have probably thanked all the meteorites that encapsulated the small substance.

But what is a meteorite? And where does it come from?

The universe consists of heavenly bodies – mainly planets, galaxies, stars, and asteroids (rocky, metallic objects that look like rocks; also known as minor planets). Some of these asteroids take a one-way trip to Earth – should they decide to continue their suicidal collision course, they become meteoroids. When a meteoroid touches our atmosphere, the friction causes it to ignite, and like a match, and burns it.

Now by theory, the meteoroid is supposed to burn up completely. However, in most cases, it doesn’t. The leftover meteoroid has no other choice but to land on the Earth’s surface. It manifests itself as a falling or shooting star (at this point, it is now called a meteor), touches ground and voila! A freshly-landed meteorite is born.

Some of the meteorites have been analyzed. It has been confirmed that their points of origin are mostly lunar (from the moon) and/or Martian (from Mars). They may look like regular rocks, but it is living proof that the existence of other life forms may not be so impossible after all.

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What are meteor storms?

Meteor storms are intense meteor showers. They may seem to radiate from just one point in the sky because the particles travel parallel to each other. Most meteor storms and showers are named after the constellation where they are nearest.

There are two particular meteor showers a stargazer should take note of:

The first would be the Perseids. It is the most regular and most visible of all the showers and is associated with a specific comet (the comet Swift-Tuttle). They peak between August 9 and 14 of every year and is said to have been observed approximately for the past 2000 years. The pre-dawn hours would be the best time to see them.

The second would be the Leonids and is claimed to be the most spectacular meteor shower. Connected with another comet (the comet Tempel-Tuttle), the meteors appear to radiate from one point – where the constellation Leo is. They say that the Leonid showers turn into a storm approximately every 33 years. But recent storm activity belies that theory as the last Leonid meteor storms were recorded in recent years: one storm in 1999 and two each for the years 2001 and 2002.

A meteor storm occurs unexpectedly. So should you be packing your bags for a meteor watching outside the city, be alert and scan the sky from time to time so that you won’t miss it.

Leonid Meteor Storm

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The L chondrite, also known as the L type of ordinary chondrites, is very common in spite of its relatively unknown status. They account for around 30 % of the categorized type of meteor, and around 40 % of the normal kind of chondrites.

The name “L chondrite” is derived from their low level of iron, as opposed to those chondrites with high levels of iron, known as the H chondrites. As for the characteristics of the L chondrite, it contains fayalite of about 25 mol %. It also contains about 5 to 10 % of nickel, which is observed as a metal. Thus, these types of meteorites are somewhat magnetic, although not as powerful as the H chondrites.

The usual minerals that are found in the L chondrite are olivine as well as hypersthenes. Nickel-iron and troilite are also observed to be found in the L chondrite. Because of the various kinds of minerals that are found in the chondrite, the meteorite usually experiences a strong kind of heating up.

Interesting to note is that when studied relative to other types of chondrites, a large part of the L chondrites have been observed to be very much devastated. This shows that the chondrite may have suffered from a strong impact.

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Photo by: Lars Lindberg Christensen Creative Commons

size of a grain of sand that before they touch earth’s surface they have crumbled. A forceful and bizarre meteor shower is termed as either a meteor storm or meter outburst. During these extraordinary events, more than a thousand meteors appear hourly.

The Zenith Hourly Rate is the number of meteors you will see in an hour. If the shower’s peak has a magnitude of 6.5, it can be discerned by the naked eye. The best way to observe and appreciate a meteor shower is when there is no moon, light pollution and cloud. A meteor shower occurs when a planet makes contact with dust or debris from a comet. This debris moves in the trail of the comet and the moment a planet moves through it, a meteor shower happens.

The Perseids is a meteor shower that has been observed in the past years with its peak clearly seen on August 12. Of all the meteor showers, it is the Leonids that stuns and impresses observers and it usually occurs sometime on the 2nd or 3rd week of November. It is noted that every 33 years, Leonids produce meteor storms with a Zenith Hourly Rate of a thousand meteors falling.

Perseid Meteor Shower

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A comet’s nucleus is comprised of ice, dust and rock. Long period comets are comets that have orbits of high eccentricity, usually resembling the shape of a parabola. Unlike the Earth and other celestial bodies that take circular or elliptical orbits, these comets that have periods over two hundred years seem to make parabolic paths. This particular kind of comet is also bound to the Sun by means of gravity. The succeeding orbit of a long period comet can be computed using the comet’s osculating orbit at every epoch after the comet has left the planetary region and the calculations are made with respect to the center of mass of the Solar System. One of the known long period comets is the Comet McNaught.

Some Beliefs About Comets

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A Meteor that has not entered Earth's atmosphere is called a meteoroid. Earth's atmosphere usually burns up most of these meteoroids (now called a meteor once it enters the Earth's atmosphere). It is the burning up of meteors which cause the bright flare seen in the sky; hence the term: fireballs.

The earth's atmosphere usually burns up most fireballs, but there are a rare few that survive both the atmosphere burn and the ground impact; these are called meteorites, and are usually found in impact craters. Some impact are so strong, the entire meteor is vaporized, leaving no trace or meteorite in its crater.

There are a few percentages of meteoroids that do enter Earth's atmosphere yet are able to escape its gravity and pass out again. These meteoroids are sometimes called Earth-grazing fireballs.

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