Breakdown: Why do meteors glow in the night sky?
MEMPHIS, Tenn. (WMC) - If you’ve spent any time outdoors at night, you’ve likely seen a “shooting star” at least once in the dark sky.
A shooting star isn’t a star at all. It is really a small piece of rock or dust that hits Earth’s atmosphere from space. Think of them as “space rocks.”
- Most meteors burn up in the atmosphere before they reach the ground. However, once in a while a meteor is large enough than some of it survives and reaches Earth’s surface. Then it is called a meteorite.
But what causes them to glow? When meteoroids enter Earth’s atmosphere (or that of another planet, like Mars), it moves so fast that it heats up, causing it to “glow” as it moves through the atmosphere. When they plow through the atmosphere, meteors are heated to more than 3,000 degrees Fahrenheit!
They move at a tremendous velocity:
- Meteoroids (meteors traveling in space) can orbit the Sun at a velocity of up to 26 miles per second (42 kilometers per second)
- When these meteoroids encounter the Earth, they may enter the atmosphere at speeds ranging from 25,000 to 160,000 miles per hour, or roughly 45 miles per second (72 kilometers per second).
Meteors light up almost as soon as they hit Earth’s atmosphere. The friction the meteoroids experience within the Earth’s atmosphere is what causes the meteor to produce light (and to ultimately disintegrate before reaching the Earth’s surface).
According to NASA, that bright streak is not actually the rock, but rather the glowing hot air as the hot rock zips through the atmosphere.
On average, when you see a meteor, you’re looking at a piece of dust burning bright about 50 to 75 miles (80 to 120 km) in altitude above Earth’s surface. But the height at which they entirely burn up in the atmosphere varies.
- Very rarely a meteoroid with sufficient size will enter the Earth’s atmosphere and remnants of the original mass will survive the journey through the atmosphere. These remnants are called meteorites.
Some meteors, such as August’s Perseids, burn up in the atmosphere at about 60 miles (100 km) above Earth’s surface. Other meteors, such as the Draconids in October, fall to about 40 miles (70 km) before they heat up enough to glow and vaporize.
The difference is that the Draconids are much slower meteors than the Perseids. The height in the atmosphere at which a meteor begins to glow depends on its arrival speed.
Here are some meteor arrival speeds, according to EarthSky.org
- Leonids: 44 miles (71 km) per second
- Perseids: 38 miles (61 km) per second
- Orionids: 42 miles (67 km) per second
- Lyrids: 30 miles (48 km) per second
- Geminids: 22 miles (35 km) per second
- Fall Taurids: 19 miles (30 km) per second
- Delta Leonids: 14 miles (23 km) per second
- Draconids: 14 miles (23 km) per second
Although meteors may be seen at any hour of the night, they are best seen in the hours between midnight and dawn.
According to The Astronomical League:
The reason for this is that during these hours we are facing the same direction as the Earth is moving around the Sun. Therefore we are oncoming space rather than space we leave behind. During the dark evening hours, meteoroids have to catch up with the Earth in order to collide with it. In the early morning hours, we are colliding head-on with the meteoroids and there are many more to be seen. The highest rates will occur near 6:00 a.m. and the lowest rates will occur near 6:00 p.m. It is much like the situation where a car is driving through a snowfall. Many more snowflakes will strike the front windshield than will hit the rear window.
In addition to daily variations in the meteor rate, there are variations also seen during the year. Rates of sporadic (random or non-stream) meteors are highest during the second half of the year by a factor of two. Aside from the annual showers, one can expect to see up to five meteors per hour during the winter and spring months. During the summer and fall months expect to see up to ten meteors per hour.
There are a dozen major meteor showers every year, and many more minor ones.
METEOR SHOWER CALENDAR 2021-2022
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