Dozens of asteroids orbit throughout the galaxy, but the most famous are those that have impacted the Earth. Asteroids that do are best known by the major craters they leave behind. The Vredefort crater was created by an asteroid nearly two billion years ago in South Africa. The crater has a radius of 118 miles and is believed to be the largest asteroid crater.
Comets are made up of collections of ice, dust and rocky particles that are leftover from the formation of the solar system 4.6 billion years ago. Comets range in length from a few kilometers to tens of kilometers. The nuclei are comprised of frozen gases such as carbon dioxide, carbon monoxide, methane and ammonia.
The bright green color of some meteorites is caused by the internal combustion of metals as they pass through the upper atmosphere. Many asteroids are rich in nickel and have trace amounts of copper. Both metals burn green when sufficiently heated.
The average speed of an asteroid is 25 kilometers per second. Depending upon the size and velocity of an asteroid, a collision with Earth could have catastrophic effects.
Mankind has dreamed of mining asteroids ever since the 19th century sci-fi serial "Edison's Conquest of Mars," but it has only come within scientific reach very recently. Asteroids are rich in metals found only in scarce quantities on Earth. If scientists figure out a way to tow an asteroid into the orbit of the moon, they can effectively harvest millions of dollars worth of minerals from even relatively small asteroids.
Ukrainian scientists discovered a large asteroid in late 2013 that could possibly strike the Earth on Aug. 26, 2032. If such a collision occurred, it would strike with a force 50 times greater than the largest atomic bomb.
Though stars are shining in the sky at all times, they are not visible during the day because the sun's brightness overpowers the dimmer stars. At night, without interference from the sun's rays, the other stars become visible.
Recent sightings of great comets, or comets bright enough to be seen without the aid of special equipment, are Comet Lovejoy in 2011, Comet McNaught in 2007, Comet Hale-Bopp in 1997, Comet Hyakutake in 1996, Comet West in 1976, Comet Ikeya-Seki in 1965, Comet Skjellerup-Maristany in 1927 and Halley's Comet in 1910. Numerous comets too dim to be seen by anyone but astronomers regularly pass through the solar system.
Asteroids are formed from the leftovers of the formation of our solar system from about 4.6 billion years ago. Early on, the birth of Jupiter prevented any planetary bodies from forming in the gap between Mars and Jupiter, causing the small objects that were there to collide with each other and fragment into the asteroids seen today.
Cosmic rays are fast-moving elementary particles, such as protons, electrons and atomic nuclei, that strike the Earth from outer space. They travel almost at the speed of light. Scientists believe they originate from supernovas, black holes and quasars.
The asteroid belt is a region of the solar system between Mars and Jupiter where the majority of the asteroids in the solar system are found. Millions of asteroids are believed to be located in this region.
A comet is a frozen collection of rocks, gases and dust that orbits around the sun, while a meteor is a piece of debris that comes into contact with a planet's atmosphere. Before it collides with a planet, a meteor is called a meteoroid.
The burning meteor that causes a shooting star can vary from the size of a grain of sand to a 1-meter-long object. As the meteor falls through the atmosphere, it burns up and gives the appearance of a star falling.
Comets begin as a mixture of ice and dust and end up losing their ice and gases each time they orbit around the sun. They come from the Kuiper Belt and the Oort Cloud. After around 500 passes, they lose most of their ice and gas content and eventually turn into something close to an asteroid.
According to the Center for Meteorite Studies at the Arizona State University, meteorites are believed to come from the asteroid belt between Mars and Jupiter. Hubblesite defines a meteorite as a meteor or a piece of meteor that makes it through the atmosphere and lands on earth.
Giuseppe Piazzi discovered the first and largest asteroid, Ceres, on Jan. 1, 1801, while mapping stars. He found it orbiting in an area between Mars and Jupiter. Measuring 583 miles across, this almost spherical asteroid contains about one-fourth of the mass of all known asteroids.
Meteors burn up in the mesosphere when they encounter the molecules from that layer and rub up against them. This generates heat; ironically, the mesosphere is the coldest part of the atmosphere.
Meteors from Mars arrive on Earth as the result of impacts on the planet by other bodies, which launch material out into space. Some of this debris is pulled in by the gravity of the Earth, falling as Martian meteorites.
Scientists predict that Halley's Comet, also known as Comet Halley, will make an appearance again in late 2061, early 2062. It was last seen in the sky in 1986.
Unlike other meteor showers, the Draconid meteor shower is not confined to a specific area of the sky, so the best way to watch them is to find a location away from the lights of the city, lie back on a blanket, and prepare to spend at least two hours gazing at the sky. When sky-gazing for the Draconid meteors it's best to point your feet in a north-to-northwest direction.
Comets travel between 26 miles per second and 298 miles per second. The speed depends on two factors: the shape of its orbit and its proximity to the Sun at a particular point in time.