This is called a meteor shower. This photo was taken during the Perseid meteor shower, which happens each year in August. Because meteors leave streaks of light in the sky, they are sometimes confused with comets.
However, these two things are very different. You can see a comet even when it is very far from Earth. When they land on Earth, they are called meteorites. A scientist investigates a meteorite that landed in Sudan's Nubian Desert in Image credit: NASA. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Create Account See Subscription Options.
Continue reading with a Scientific American subscription. When a comet nears the sun, the nucleus warms up and the ice begins to sublimate from solid to gas. This produces an atmosphere surrounding the comet that can grow to thousands of miles in diameter, called a coma.
Radiation pressure from the sun blows away the dust particles in the coma to produce a long, bright dust tail. A second tail is formed when high-energy solar particles ionize the gas, creating a separate ion tail. The difference between the composition of asteroids and comets is likely due to how and where they were born, wrote Britt Scharringhausen , a professor of astronomy at Beloit College in Wisconsin.
At the center of the nebula, the sun was being born through gravitational collapse. Because of this collapse, which releases heat, the central regions of the nebula were hotter and denser, while the outer regions were cooler. Asteroids formed near the center of the hot nebula where only rock or metal remained solid under extreme temperatures.
Comets formed beyond what's called the frost line, where it was cold enough for water and gases like carbon dioxide to freeze. Because of this, comets generally are found only in the far reaches of the solar system in two regions named the Kuiper Belt and the Oort Cloud. Meteoroids are the true space rocks of the solar system. Asteroids typically consist of rocks or metals. In disaster movies, the big space rock that might destroy the entire planet is usually an asteroid.
Just saying. Where do asteroids come from? There are currently more than 1 million known asteroids in the solar system. Most of the asteroids we know about are in the asteroid belt , a kind of junkyard for asteroids between Mars and Jupiter. This sets them apart from asteroids, which are mostly rock or metal. Like asteroids, though, comets often orbit the sun. When comets get close to the sun, it heats their icy core, forming a halo or coma of dust and gas.
Comets are known for having a tail, which is really the trail that happens when this gaseous dust cloud is blown by solar wind or heat.
Where do comets come from? Most comets come from outside of or from the edge of the solar system. Many come from the far-out regions known as the Oort Cloud where there are billions of them and the Kuiper Belt. Some orbit the sun, while others escape on a path out of the solar system.
Those that orbit the sun come around in regular intervals, which makes some of them famous visitors. The term shooting star or falling star is just a more poetic name for a meteor , which can look a little bit like a star as it makes a bright streak through the sky. Since they happen so fast, you have to be pretty lucky to see a shooting star as it happens—unless you know that a meteor shower is coming.
Well done! Whether you need one-on-one or group study sessions, Dictionary Academy tutoring is custom-fit to meet your learning needs. Feedback Tired of Typos? Word of the Day.
0コメント