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8 chapters in this video
0:00 Introduction to asteroids.1:30 What is an asteroid made of, and what does it look like? 2:33 Asteroid between Mars and Jupiter 3:37 Can you see asteroids from Earth? 4:35 Are there asteroids near Earth? 4:59 Other cool facts about asteroids 5:34 How to see an asteroid from Earth 6:02 Review of asteroids
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In this video, you will learn specifically about asteroids. Sometimes when you look at the night sky, you will see lots of lights in the sky. But not all of those shiny spots are starts. A few of them are planets. And a couple of them are actually asteroids! Asteroids can be as small as a speck of dust, and they can be hundreds of miles in diameter! They are made of mostly rock, but they might contain clay or silicon, or even metal. Those metals are usually nickel or iron, but some asteroids contain precious metals like gold and platinum.
The asteroid belt between Mars and Jupiter contains most of the asteroids in our solar system. There are around a million asteroids that are over half a mile long! And there are millions more that are smaller. Ceres is the biggest asteroid in the belt, maybe even the solar system. It is so big that scientists consider it a dwarf planet! While most asteroids can't be seen from Earth, Vesta can be. Vesta is the second largest asteroid in the belt, but it is the brightest one in the sky. If it's in the right position, you can see it with the naked eye!
Exploring the World of Asteroids
What Is an Asteroid?
What Is an Asteroid?
An asteroid is a chunk of rock and metal in outer space that is in orbit around the Sun. Asteroids vary in size from just a few feet across to hundreds of miles in diameter.
Most asteroids are not round, but are lumpy and shaped like a potato. As they orbit the Sun, they tumble and spin.
Asteroids are small, rocky objects that orbit the sun. Although asteroids orbit the sun like planets, they are much smaller than planets.
There are lots of asteroids in our solar system. Most of them live in the main asteroid belt—a region between the orbits of Mars and Jupiter.
Most asteroids in our solar system can be found in the asteroid belt, between Mars and Jupiter.
Asteroids hang out in other places, too. For example, some asteroids are found in the orbital path of planets. This means that the asteroid and the planet follow the same path around the sun. Earth and a few other planets have asteroids like this.
Where did asteroids come from?
Where did asteroids come from?
Asteroids are left over from the formation of our solar system. Our solar system began about 4.6 billion years ago when a big cloud of gas and dust collapsed. When this happened, most of the material fell to the center of the cloud and formed the sun.
Some of the condensing dust in the cloud became planets. The objects in the asteroid belt never had the chance to be incorporated into planets. They are leftovers from that time long ago when planets formed.
Are all asteroids the same?
Are all asteroids the same?
No way! Because asteroids formed in different locations at different distances from the sun, no two asteroids are alike. Here are a few ways that they differ:
Asteroids aren’t all round like planets. They have jagged and irregular shapes.
Some asteroids are hundreds of miles in diameter, but many more are as small as pebbles.
Most asteroids are made of different kinds of rocks, but some have clays or metals, such as nickel and iron.
Types of Asteroids
There are three main types of asteroids based on what type of elements make up the asteroid. The main types include carbon, stony, and metallic.
Carbon - Carbon asteroids are also called carbonaceous asteroids. They are made up mostly of rocks rich in the element carbon. They are very dark in color. Around 75% of all asteroids are the carbon type.
Stony - Stony asteroids are also called silicaceous asteroids. They are made up of mostly rock and some metal.
Metallic - Metallic asteroids are made up of mostly metals, primarily iron and nickel. They often have some small amounts of stone mixed in.
Photo: Meteor Crater in Arizona. This 1.2 km in diameter and 170 meters deep crater was formed by a 40- to 50-meter iron-nickel asteroid roughly 50,000 years ago.
Could an asteroid hit Earth?
Yes, not only could an asteroid hit Earth, but many asteroids have already struck Earth. These asteroids are called Near-Earth asteroids and they have orbits that cause them to pass close to the Earth. It is estimated that an asteroid larger than 10 feet across strikes the Earth around once a year. These asteroids usually explode when they hit the Earth's atmosphere and cause little damage on the Earth's surface.
Largest Asteroids
Some asteroids are so large that they are considered minor planets. Others are very small.
The four largest asteroids are:
Ceres, Vesta, Pallas, and Hygiea.
Ceres - Ceres is by far the largest asteroid. It is so big that it is categorized as a dwarf planet. Ceres is 597 miles in diameter and contains around one 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. Vesta is more massive than Pallas, but slightly smaller in size. It is the brightest asteroid when viewed from Earth and was named after the Roman goddess of the home.
Pallas - Pallas was the second asteroid to be discovered after Ceres. It is the largest body in the Solar System which 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 roughly 220 miles wide by 310 miles long.
Asteroid Belt
The majority of 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.
he asteroid belt is a vast region of space that is home to millions of asteroids. The asteroids are made up of the same materials as the planets, but they never formed into a planet themselves. The asteroid belt is thought to be the remains of a planet that was destroyed early in the history of the solar system.
The asteroid belt is a relatively safe place for Earth. The asteroids in the belt are mostly small, and they rarely come close to Earth. However, there is always a small chance that a large asteroid could hit Earth, and this is something that scientists are constantly monitoring.
Trojan Asteroids
There are other groups of asteroids outside the asteroid belt. One major group is the Trojan asteroids. Trojan asteroids share an orbit with a planet or a moon. However, they don't collide with the planet. The majority of the Trojan asteroids orbit the sun with Jupiter. Some scientists think there may be as many Trojan asteroids as there are asteroids in the belt.
In 2016, NASA launched the OSIRIS-REx spacecraft to study an asteroid near Earth named Bennu. After studying Bennu for a few years, OSIRIS-REx scooped up a sample of dust and rocks from the asteroid’s surface.
Now, OSIRIS-REx is headed back to Earth! Its sample container will land in the Utah desert in September 2023. Scientists will then collect the container and examine the dust and rocks for clues about how planets formed and life began.
What can we learn from asteroids?
What can we learn from asteroids?
Since asteroids formed at the same time as other objects in our solar system, these space rocks can give scientists lots of information about the history of planets and the sun. Scientists can learn about asteroids by studying meteorites: tiny bits of asteroids that have flown through our atmosphere and landed on Earth’s surface.
Several NASA space missions have also flown by and observed asteroids. The NEAR Shoemaker spacecraft landed on Eros, an asteroid near Earth, in 2001. Then, the Dawn spacecraft traveled to the asteroid belt in 2011. It orbited and studied the giant asteroid Vesta and the dwarf planet Ceres.
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 over one million asteroids larger than 1km in diameter within the asteroid belt.
The five largest asteroids make up 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 the Earth.
Famous People
Julius Caesar (100 BC–44 BC) was a politician and general in Ancient Rome who helped build the powerful Roman Empire. He made enemies along the way and was eventually assassinated just a year after he was declared “dictator for life”.
Did You Know?
Did you know that Julius Caesar invented our calendar system? The Roman calendar had 355 days in a year, based on the moon’s cycle. Caesar proposed a more accurate ‘Julian’ calendar using the time it takes the earth to revolve around the sun - 365 ¼ days - with a “leap year” every four years to cover the quarter. Today, we use a slightly altered version called the Gregorian calendar. His birthday month was also renamed Julius (July) in his honour.
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