What is an Asteroid?
A asteroid It is a chunk of rock and metal in outer space that orbits the Sun.
The asteroids they range in size from a few feet across to hundreds of miles in diameter.
Most of the asteroids they are not round, but are potato shaped. As they orbit the Sun, they go round and round.
Asteroids are rocky worlds revolving around the sun that are too small to be called planets.
They are also known as planetoids or minor planets. There are millions of asteroids, ranging in size from hundreds of miles to several feet in diameter. In total, the mass of all asteroids is less than that of Earth’s moon.
Despite their size, asteroids can be dangerous. Many have crashed into Earth in the past, and many more will crash into our planet in the future.
That’s one of the reasons scientists study asteroids and are eager to learn more about their numbers, orbits, and physical characteristics. If an asteroid is headed our way, we want to know about it.
Training
Asteroids are leftovers from the formation of our solar system about 4.6 billion years ago.
At first, the birth of Jupiter prevented planetary bodies from forming in the space between Mars and Jupiter, causing the small objects there to crash into each other and break up into the asteroids seen today.
The understanding of how the solar system evolved is constantly expanding. Two fairly recent theories, the Nice model and the Grand Tack, suggest that the gas giants moved before settling into their modern orbits.
This movement could have sent asteroids from the main belt raining down on the terrestrial planets, emptying and refilling the original belt.
physical characteristics
Asteroids can become as large as Ceres, which is 940 kilometers (about 583 miles) in diameter.
At the other end of the scale, the smallest asteroid ever studied is the 6-foot-wide (2-meter) space rock 2015 TC25, which was observed when it made a close approach to Earth in October 2015.
The chances of it hitting Earth in the foreseeable future are small, Vishnu Reddy of the University of Arizona Lunar and Planetary Laboratory said in a statement.
«You can think of[un asteroide] like a meteor floating in space that hasn’t hit the atmosphere and hit the ground, yet,» Reddy added.
Almost all asteroids are irregularly shaped, although some of the largest are almost spherical, like Ceres.
the vesta
For example, Vesta has a giant crater about 285 miles (460 km) in diameter. The surfaces of most asteroids are thought to be covered in dust.
As asteroids revolve around the sun in elliptical orbits, they rotate, sometimes circling quite erratically.
It is also known that more than 150 asteroids have a small companion moon, and some have two moons.
There are also binary or double asteroids, in which two asteroids of roughly the same size orbit each other, and triple asteroid systems are also known.
Many asteroids have apparently been captured by a planet’s gravity and become moons – likely candidates include the moons of Mars, Phobos and Deimos, and most of the outer moons of Jupiter, Saturn, Uranus and Neptune.
The average surface temperature of a typical asteroid is -100 degrees Fahrenheit (-73 degrees Celsius).
Asteroids have remained almost unchanged for billions of years – as such, research on them could reveal much about the early solar system.
Asteroids come in a variety of shapes and sizes. Some are solid bodies, while others are small piles of debris held together by gravity.
One, which orbits the sun between Neptune and Uranus, comes with its own set of rings. Another has not one, but six tails.
types of asteroids
There are three main types of asteroids based on the type of elements that make up the asteroid.
The main types include carbon, stony and metallic.
Carbon – Carbon asteroids are also called carbonaceous asteroids. They are formed mostly by rocks rich in the element carbon. They are very dark in color. About 75% of all asteroids are of the carbon type.
stony – Stony asteroids are also called siliceous asteroids. They are made up mostly of rock and some metal.
metallic – Metallic asteroids are composed primarily of metals, primarily iron and nickel. They often have some small amounts of stones mixed in.
Asteroid belt
Most asteroids orbit the Sun in a ring called the asteroid belt. The asteroid belt is located between the planets Mars and Jupiter.
You can think of it as a belt between the rocky planets and the gas planets. There are millions and millions of asteroids in the asteroid belt.
The largest asteroids
Some asteroids are so large that they are considered minor planets. The four largest asteroids are Ceres, Vesta, Pallas, and Hygiea.
Ceres
Ceres is by far the largest asteroid. It is so large that it is classified as a dwarf planet. Ceres has a diameter of 597 miles and contains about a third of the total mass of the asteroid belt. It is named after the Roman goddess of the harvest.
Vesta
Vesta has a diameter of 329 miles and is considered a minor planet. Likewise Vesta is more massive than Pallas, but slightly smaller. It is the brightest asteroid seen from Earth and is named after the Roman goddess of the home.
pallas
Pallas was the second asteroid discovered after Ceres. It is the largest body in the Solar System that is not round. It is named after the Greek goddess Pallas Athena.
Hygiea
Hygiea is the largest of the carbon-type asteroids. It is named after the Greek goddess of health. It is approximately 220 miles wide by 310 miles long.
Trojan Asteroids
There are other groups of asteroids outside the asteroid belt. An important group are the Trojan asteroids.
Trojan asteroids share an orbit with a planet or moon. However, they do not collide with the planet.
Most of the Trojan asteroids orbit the sun with Jupiter. Some scientists believe that there may be as many Trojan asteroids as there are asteroids in the belt.
Could an asteroid hit Earth?
Yes, not only could an asteroid hit Earth, but many asteroids have already hit Earth.
These asteroids are called near-Earth asteroids, and they have orbits that make them pass close to Earth.
An asteroid larger than 10 feet in diameter is estimated to hit Earth about once a year.
These asteroids usually explode when they hit Earth’s atmosphere and do little damage to Earth’s surface.
Interesting facts about asteroids
Italian astronomer Giuseppe Piazzi discovered the first asteroid, Ceres, in 1801.
The word asteroid comes from a Greek word meaning «star-shaped.»
Scientists estimate that there are more than a million asteroids larger than 1 km in diameter within the asteroid belt.
The five largest asteroids account for more than 50% of the total mass of the asteroid belt.
Some scientists have theorized that the extinction of the dinosaurs was caused by a large asteroid colliding with Earth.
Classification of asteroids
Asteroids are found within three regions of the solar system. Most asteroids lie in a vast ring between the orbits of Mars and Jupiter.
This main asteroid belt contains more than 200 asteroids larger than 60 miles (100 km) in diameter.
Scientists estimate that the asteroid belt also contains between 1.1 and 1.9 million asteroids larger than 1 km (3,281 ft) in diameter, and millions of smaller asteroids.
Not everything in the main belt is an asteroid – Ceres, once thought of only as an asteroid, is now also considered a dwarf planet.
In the past decade, scientists have also identified a class of objects known as «main belt asteroids,» small rocky objects with tails.
main belt
While some of the tails form when objects hit an asteroid, or break up asteroids, others may be comets in disguise.
Many asteroids lie outside the main belt. Trojan asteroids orbit a larger planet at two special locations, known as Lagrange points, where the gravitational pull of the sun and planet are balanced.
Jupiter’s Trojans are the most numerous, with a population almost as high as that of the main asteroid belt. Neptune, Mars, and Earth also have Trojan asteroids.
AENs
Near-Earth asteroids (NEAs) circle closer to Earth than the sun. Love asteroids have close orbits that approach but do not cross Earth’s path, according to NASA.
In addition to asteroid classifications based on their orbits, most asteroids fall into three classes based on their composition:
C-type or carbonaceous asteroids are grayish in color and are the most common, including more than 75 percent of known asteroids. They probably consist of stony clay and silicate rocks, and inhabit the outer regions of the main belt.
S-type, or siliceous, asteroids are greenish to reddish in color, make up about 17 percent of known asteroids, and dominate the inner asteroid belt. They appear to be made of silicate and nickel-iron materials.
M-type or metallic asteroids are reddish in color, make up most of the rest of the asteroids and inhabit the middle region of the main belt. They appear to be made of nickel-iron.
There are many other rare types based on composition as well – for example, the type V asteroids typified by Vesta have a volcanic basaltic crust.
ground impacts
Since Earth formed about 4.5 billion years ago, asteroids and comets have routinely smashed into the planet. The most dangerous asteroids are extremely rare, according to NASA.
An asteroid capable of global disaster would have to be more than a quarter of a mile across.
Researchers have estimated that such an impact would kick up enough dust into the atmosphere to effectively create a «nuclear winter.» Which would severely disrupt agriculture around the world.
Asteroids that size hit Earth only once every 1,000 centuries on average, NASA officials say.
The little ones
Smaller asteroids thought to hit Earth every 1,000 to 10,000 years could destroy a city or cause devastating tsunamis.
According to NASA, space rocks smaller than 25 m (82 ft) are very likely to burn up upon entering Earth’s atmosphere.
Which means that…