What makes meteors visible

This extreme speed is what allows these tiny objects to burn so brightly. The kinetic energy an object carries is proportional to its mass multiplied by its velocity squared, meaning that minuscule grains moving really fast carry vast amounts of energy. There is some confusion over what is meant by particular terms, which are often mixed up in casual conversation, and the popular press. Meteoroid: Any piece of small rock, metal or ice moving through space. The closer you look, the more pieces of debris there are, although the smallest are quickly blown to interstellar space by the radiation pouring from our sun.

Meteorite: If an object makes it through the atmosphere to reach the ground, it is called a meteorite. Meteorites range from a few grams to many tonnes in mass, with the smallest and lightest falling most frequently. The most massive meteorite found to date is the Hoba meteorite , from Namibia, with a mass of about 66 tonnes.

Fireball: A meteor that is unusually bright, outshining almost everything in the night sky. Typically, any meteor brighter than magnitude -4 i. These minuscule grains are more like particles of smoke. When scientists study newly recovered meteorites, they break them up into two types — falls and finds. Most meteorites are located long after they fell, often years or even centuries ago, so they will have suffered the effect of weathering and chemical processes here on Earth.

These are meteorites whose passage through the atmosphere has been observed and reported. This allows scientists to find them before they have been affected by weathering or other processes on Earth. One such is the Australian Desert Fireball Network which you can help by reporting any particularly spectacular fireball you see, just in case something fell that can be recovered.

That's because all the meteors are coming at us at the same angle, and as they get closer to Earth the effect of perspective makes them seem to get farther apart. It's like standing in the middle of railroad tracks and seeing how the two tracks come together in the distance.

Meteor showers are named for the constellation where the meteors appear to be coming from. So, for example, the Orionids Meteor Shower, which occurs in October each year, appear to be originating near the constellation Orion the Hunter.

Here are dates of major meteor showers. Peak viewing times will vary by a day or two each year. Keep in mind: If the moon is full or near full, you may not see many meteors. Some years are better than others for numbers of meteors per hour. Bring blankets, a sleeping bag, and a thermos of something warm to drink. Hot chocolate, perhaps? Lie down and get warm and cozy. This is a meteor, a glowing trail caused by the incineration of a piece of celestial debris entering our atmosphere.

Many meteors are quick flashes, but some last long enough for us to track their brief course across the sky. Now and then, a meteor truly will light up the night, blazing brighter than Venus — and although rarely, even brighter than the Moon — leaving in its wake a dimly glowing trail that may persist for minutes. Under a dark sky, any observer can expect to see between two and seven meteors each hour any night of the year. These are sporadic meteors; their source bodies — meteoroids — are part of the dusty background of the inner solar system.

Several times during the year, Earth encounters swarms of small particles that greatly enhance the number of meteors. The result is a meteor shower, during which observers may see dozens of meteors every hour. Concentrations of material within the swarms may produce better-than-average displays in some years, with rates of hundreds per hour. And every now and then, we're treated to a truly spectacular display in which thousands of visible meteors can be seen for a brief period.

These are referred to as meteor storms. The meteors that appear during a meteor shower seem to radiate from one point in the sky. This illusion is an effect of perspective, just as a roadway seems to converge in the distance.

Usually, meteor showers take the name of the constellation from which the meteors appear to radiate. For example, during the Perseid shower in August, meteors seem to streak from a point in the constellation Perseus.

The science of meteor astronomy began in , when a storm of 60, meteors an hour shocked the world. By the s, it had become clear that many meteor showers were annual — including the normally placid Leonids, which produced the big storm — and that they were somehow related to comets.

Astronomers now consider comets to be "dirty snowballs" consisting of a mixture of dust and frozen gases. A comet becomes visible only during its closest approach to the Sun, when areas on the comet's icy surface become warm enough to evaporate.

The resulting jets of evaporating gases carry with them any solid matter mixed with the original ice. At each pass near the Sun, the comet ejects a stream of material. The particles composing the stream orbit the Sun in slightly different paths than the source comet. Each particle receives small accelerations from forces other than gravity, and these orbits become increasingly modified over time.

The ejected streams become more diffuse with age and lose their individual identities. Concentrated initially near the comet, the debris diffuses along each stream's orbit and eventually forms a thin band of material that Earth encounters every year.

A meteor shower occurs on the date in the year when Earth passes nearest to the band of material associated with a comet's orbit. Most of the meteors seen during one of the annual showers arise from fluffy particles not much larger than sand grains.

As a particle enters Earth's atmosphere, it collides with gas atoms and molecules. The particle becomes wrapped in a glowing sheath of heated air and vaporized material boiled off its own surface.

Meteors become visible at altitudes between 50 and 75 miles 80 and kilometers , with faster particles typically shining at greater heights.

Many of the faster, brighter meteors may leave behind a train — a dimly glowing trail that persists for many seconds or, more rarely, minutes. Larger debris may create a fireball — a spectacular meteor bright enough to outshine even Venus. Occasionally, a fireball will fragment; this event is accompanied by bright flares and even "sparks" thrown a short distance from the meteor's main trail.

Such a fireball is called a bolide. The best way to enjoy a meteor shower is to dress warmly, set down a blanket or lawn chair at a dark site, get comfortable, and watch the stars. On any night of the year, meteors appear faster, brighter, and more numerous after midnight. That's when your location has turned into Earth's direction of motion around the Sun and plows into meteor particles nearly head-on, rather than having them catch up from behind.

The meteorite was found buried 10 feet 3 meters deep in the ground. It weighed 2, lbs. The most famous meteorite crater in the United States is misnamed Meteor Crater.

It's in Arizona, and it's huge. The rim rises feet 45 m from the surrounding plain, and the hole is feet m deep and nearly a mile wide. It was the first crater that was proven to be caused by a meteorite impact, which occurred between 20, and 50, years ago. Meteors are often seen falling from the sky alone — one here, one there. But there are certain times in a year when dozens or even hundreds of meteors per hour will light up the sky, seemingly coming from one part of the sky, radiating in all directions, and falling toward Earth one after the other.

There are several periodic meteor showers that astronomers and amateur observers wait for every year. Meteor showers are named after the constellations from where the shower appears to be coming from.

For example, the Orionids appear to originate from the mighty Orion constellation, while Perseid meteors seem to be coming from the Perseus constellation. Leonids: The brightest and most impressive is the Leonid meteor shower , which can produce a meteor storm that showers the sky with thousands of meteors per minute at its peak. In fact, the term "meteor shower" was coined after astronomers' observed one of Leonids' most impressive displays in The Leonids occur every November, but the shower's most beautiful display happens at intervals of about 33 years, with the last one lighting Earth's sky in ; it is not expected to be repeated until Related: Amazing Leonid meteor shower photos.

Perseids: Another shower that is worth keeping awake for is the Perseid meteor shower , which is associated with the Comet Swift-Tuttle , which takes years to orbit the sun. Earth passes through the comet's orbit during the month of August every year. It is not as active as the Leonids, but it is the most widely watched meteor shower of the year, peaking on Aug. Orionids: The Orionid meteor shower produces meteors from Halley's comet , which orbits the sun every 75 to 76 years.

The Orionid shower happens every October and can last for a week, treating patient observers to a show of 50 to 70 shooting stars per hour at its peak. Related: Orionid meteor shower sparks bright fireballs video. Quadrantids: The Quadrantid meteor shower comes from the debris of an asteroid called EH1, which some astronomers think was part of a comet that broke apart centuries ago.