Asteroid Belt Intorduction
The largest asteroid in the solar system is 2001 KX76. In the asteroid belt, the largest asteroid is Ceres, which is 933 kilometers across. The next largest, which is called Vesta, is 530 kilometers across.
Some asteroids are less than a kilometer across. Unofficially the limit has been set at 50 meters, and anything smaller than that is going to be simply called a meteoroid. With advances in telescopes and particularly for objects that travel close to the Earth, some objects smaller than 50 metres have indeed been seen passing nearby the Earth.
There are probably several million asteroids in the solar system. Over 96,000 asteroids have been given numbers. Almost 12,000 of them have names. But even though there are a lot of asteroids, the asteroid belt is mostly empty space. Traveling through the asteroid belt in a space ship would not be very much like what you see in a science fiction film.
The asteroid belt lies between the planets Mars and Jupiter. It contains lumps of rock and metal much smaller than planets. These lumps are called asteroids or minor planets. They are not visible from Earth with the naked eye, but many may be seen through binoculars or small telescopes.
Asteroid Belt Names After
The first asteroids were named after mythical heroes and gods much like the major planets. The first to be discovered was named Ceres after the Roman goddess of growing plants (particularly grain) and of motherly love. The second asteroid discovered was called Pallas and was named after one of the Greek gods of wisdom. Asteroids are also given a number in the order of their discovery, so Ceres is 1, Pallas is 2, and so forth.
As the number of known asteroids increased, they ran out of mythical names so other names were used instead. Some asteroids were named after countries. For example asteroid number 136 is named Austria. Others were named after plants, for example 978 Petunia. 1620 Geographos was named after the National Geographic Society, in recognition to their efforts at sharing knowledge about the Solar System. Many are named after people, both alive and dead. In a couple of cases, like 2309 Mr. Spock, asteroids were named after the discover's pet cat. This last type of naming is discouraged, but it still happens from time to time. Even fictional characters have been used.
Today, names for asteroids can be suggested by the people who discover them. The names become official after a group of people reviews them to make sure they are not offensive or too much like another name. Because so many asteroids are now being found, most new asteroid discoveries are not even getting a name at all, but rather a numbered code. It is not likely that they will ever be given a formal name, at least in this century.
Asteroid Belt Discovery
Asteroid Belt Facts:
1.The total weight of all the asteroids in the asteroid belt is about 1/35th of that of our moon. 2.Its largest object in the asteroid belt, Ceres, makes about 1/3 of the total weight of all the asteroids. 3.Ceres is the only dwarf planet in the asteroid belt.
The first asteroid to be discovered was Ceres, on 1 January 1801, by Giuseppe Piazzi accidentally. At first he thought this was a comet, then later a planet! When it was realised it was too small Sir William Herschel (the astronomer who discovered Uranus) made up the word "asteroid" to describe it, using the Latin word aster, meaning star, and the -oid, meaning rock or planet. In other words a star-like planet, because he couldn't see any details due to the small size of the object.
By 1807 another 3 asteroids were discovered, but no more were found until 1845 when a persistent asteroid hunter named Karl Ludwig Hencke found a fifth, and sixth asteroid in 1847. Ever since then at least one new asteroid has been found each year.
In 1891, the first pictures of the night sky were taken to find more asteroids. This led to the discovery of many more asteroids. A picture of the same part of the sky is taken on two different nights. When the two pictures are lined up, the stars will be in the same places but an asteroid will have moved.
In our modern times, over 280,000 asteroids have been discovered. Many more are being found all the time. Some of these asteroids pass near the earth and astronomers want to find any that come close to our planet. Large numbers of asteroids are now being discovered by machines.
Asteroid Belt is Made Of?
Three out of four asteroids are made of rock that is rich in carbon. The rest are made of the metals iron and nickel. About half of these are pure iron and nickel; the rest are mixed with compounds of silica, the element that makes up rocks. Each of the larger metal asteroids contains huge amounts of iron: much more than is mined every year on Earth.
Scientists are very interested in what asteroids are made of because it can help them learn how the solar system was formed. Several spacecraft have visited asteroids to learn more about themAre there asteroids outside of the asteroid belt?Most asteroids are found in the asteroid belt, but not all. Some asteroids orbit closer to the Sun, and many asteroids orbit beyond Neptune. Asteroids that closely approach Earth are called Near-Earth Asteroids. Sometimes pieces of asteroids strike the Earth, burning in the atmosphere as a meteor. If they are large enough, they might actually hit the surface and become meteorites.
Asteroid Ida and its moonThere are also some asteroids in the outer solar system that are called Centaurs. But it is hard to tell whether any one Centaur is an asteroid, comet, or Kuiper Belt object. For example, the first Centaur to be discovered was Chiron. But some scientists think it is a comet, not an asteroid. Officially it is called both the asteroid 2060 Chiron and the comet 95P/Chiron!
In most cases when an the orbit of asteroid crosses the path of a planet such as Jupiter, at some point the asteroid will either hit the planet or else be hurled into another orbit. Many of the small moons of some planets may have once been asteroids that were captured by the planet's gravity when they came too close. However there are two points along the orbit of a planet were an asteroid can safely linger. These are found at a point one-sixth (or 60°) of an orbit ahead of the planet, and the same distance behind the planet. These sites are called Lagrange points, and they are found where the force of gravity from the Sun and the planet balance out with the motion of the asteroid's orbit. The asteroids found in these spots are called Trojans, and they move around the Sun at the same velocity as the planet.
Famous Asteriods
The dwarf planet Ceres.2001 KX76 is now the biggest asteroid in the solar system, beating out Ceres. Ceres is one of the few asteroids that is shaped like a sphere, and it may have some ice just underneath its dusty surface.
The asteroid Ida has its own moon named Dactyl. A number of asteroid moons have now been found.
Monday, February 26, 2007
Tuesday, February 6, 2007
Gravity Pull on Mars
Gravity Pull on Mars
If you were on Mars, it would pull you down with a force about two fifths as strong as the force of Earth's gravity. You could lift objects that weigh almost three times as much compared to similar objects here on the Earth. You could jump up almost three times higher, and it would take much longer to fall to the ground from the same height.
Even though it looks as though you would be like a comic-book hero on Mars, you would still have to worry about the mass of an object. A large object that is moving forward would still crush you if you got in its way, just like it would be a problem here on the Earth, and a bullet from a gun would do just as much damage on Mars as it does on the Earth. A vehicle that travels on the surface of Mars would have the same problems trying to stop as it would on the Earth, but an interesting problem would be that because of the reduced gravity a vehicle would not "grip" the ground on Mars as strongly, making it harder to stop if you are traveling at a high speed.
Who was it named after?
In Roman mythology, Mars was the god of war and agriculture. The planet Mars was named this because Mars is red like blood.
If you were on Mars, it would pull you down with a force about two fifths as strong as the force of Earth's gravity. You could lift objects that weigh almost three times as much compared to similar objects here on the Earth. You could jump up almost three times higher, and it would take much longer to fall to the ground from the same height.
Even though it looks as though you would be like a comic-book hero on Mars, you would still have to worry about the mass of an object. A large object that is moving forward would still crush you if you got in its way, just like it would be a problem here on the Earth, and a bullet from a gun would do just as much damage on Mars as it does on the Earth. A vehicle that travels on the surface of Mars would have the same problems trying to stop as it would on the Earth, but an interesting problem would be that because of the reduced gravity a vehicle would not "grip" the ground on Mars as strongly, making it harder to stop if you are traveling at a high speed.
Who was it named after?
In Roman mythology, Mars was the god of war and agriculture. The planet Mars was named this because Mars is red like blood.
Day and Year in Mars
One day on Earth is only 39 minutes and 35 seconds shorter than a day on Mars (1.026 Earth days). A year on Mars is almost two Earth years long (687 Earth days).
Surface of Mars
The surface of Mars is dry and dusty. The highlands of the southern hemisphere have more craters than the lower areas in the northern hemisphere. One of the craters is the huge Hellas Planitia. It is about half the size of the continental United States.
There is an area on Mars called the Tharsis Bulge which has four huge volcanoes. These volcanoes have not erupted for millions of years. The largest volcano is called Olympus Mons. It is 27 km tall, making it the highest mountain in the Solar System, much higher than Mount Everest on Earth. It is 625 km across and takes up an area as big as the US state of Arizona. Mars also has a huge canyon called the Valles Marineris. It is much bigger than the Grand Canyon on Earth. It is 4000 km long, up to 7 km deep and up to 200 km wide. Scientists think that when the Tharsis Bulge was created, the surface of Mars cracked to form the Valles Marineris.
Like the Earth, Mars has ice caps at its poles. They are made from ice and frozen carbon dixoide. During the Martian winter, the southern cap grows as carbon dioxide from the atmosphere freezes.
In some places, there are channels that look like they were made by running water. So, a long time ago Mars may have had lakes and streams made of water.
There is an atmosphere on Mars, but it is very thin. There is also much more carbon dioxide in it than oxygen. (Oxygen is the gas we want when we breathe in, carbon dixoide the gas we get rid of when we breathe out.) So, we would need spacesuits to visit Mars.
There is an area on Mars called the Tharsis Bulge which has four huge volcanoes. These volcanoes have not erupted for millions of years. The largest volcano is called Olympus Mons. It is 27 km tall, making it the highest mountain in the Solar System, much higher than Mount Everest on Earth. It is 625 km across and takes up an area as big as the US state of Arizona. Mars also has a huge canyon called the Valles Marineris. It is much bigger than the Grand Canyon on Earth. It is 4000 km long, up to 7 km deep and up to 200 km wide. Scientists think that when the Tharsis Bulge was created, the surface of Mars cracked to form the Valles Marineris.
Like the Earth, Mars has ice caps at its poles. They are made from ice and frozen carbon dixoide. During the Martian winter, the southern cap grows as carbon dioxide from the atmosphere freezes.
In some places, there are channels that look like they were made by running water. So, a long time ago Mars may have had lakes and streams made of water.
There is an atmosphere on Mars, but it is very thin. There is also much more carbon dioxide in it than oxygen. (Oxygen is the gas we want when we breathe in, carbon dixoide the gas we get rid of when we breathe out.) So, we would need spacesuits to visit Mars.
Mars
Mars
Mars is nearly 7,000 kilometres (km) wide, just over half the width of the Earth. Its volume is about 15% of the Earth.
Mars is the fourth planet from the Sun. It is called a terrestrial planet because it has a rocky surface like the Earth.
It is thought that Mars has an iron core and a crust made of silicate.
Mars is nearly 7,000 kilometres (km) wide, just over half the width of the Earth. Its volume is about 15% of the Earth.
Mars is the fourth planet from the Sun. It is called a terrestrial planet because it has a rocky surface like the Earth.
It is thought that Mars has an iron core and a crust made of silicate.
Monday, February 5, 2007
What the Moon is made of?
The Moon is mostly made up of rocks and dust. The outer layer of the Moon is called the crust. The crust is about 70 km thick on the near side and 100 km thick on the far side. It is thinner under the maria and thicker under the highlands. There may be more maria on the near side because the crust is thinner. It was easier for lava to rise up to the surface.
We think the Moon has a small core (center) about 300 km across. The core is composed of solid iron. Because the core is solid, the moon does not have its own magnetic field.
The names Moon and month both come from the ancient Greek name for the Moon, Mene. There have been other names for the Moon, like Selene and Luna. Selene was the Greek goddess of the Moon. Luna was the Roman goddess of the Moon. The Roman people also associated their goddess Diana with the Moon.
We think the Moon has a small core (center) about 300 km across. The core is composed of solid iron. Because the core is solid, the moon does not have its own magnetic field.
The names Moon and month both come from the ancient Greek name for the Moon, Mene. There have been other names for the Moon, like Selene and Luna. Selene was the Greek goddess of the Moon. Luna was the Roman goddess of the Moon. The Roman people also associated their goddess Diana with the Moon.
Day and Year on the Moon
Day
The Moon takes just over 98 Earth days to rotate (spin around) once.
Year
The Moon also takes just over 59.3 days to orbit (move around) the Earth. This is why we always see the same side of the Moon when we look from the Earth. We call this side the near side. The other side we call the far side. In 1959 a probe sent back pictures of the far side. That was the first time anyone saw what it looked like.
The Moon takes just over 98 Earth days to rotate (spin around) once.
Year
The Moon also takes just over 59.3 days to orbit (move around) the Earth. This is why we always see the same side of the Moon when we look from the Earth. We call this side the near side. The other side we call the far side. In 1959 a probe sent back pictures of the far side. That was the first time anyone saw what it looked like.
Surface of the Moon
Surface of the Moon
The Moon does not have any atmosphere. It also doesn't have any liquid water on its surface. During the day it becomes very hot, but at night it is icy cold. A person visiting the Moon needs an air supply and a special suit.
The Moon has many craters on its surface. The largest one is called the South Pole-Aitken Basin and is roughly 2500 km across.
We think nearly all the craters on moons or planets were made by huge rocks hitting them a long time ago. They are called impacts.
Some of the craters on the Moon look as if they have rays coming out of them. These rays are rocks thrown across the Moon by the impacts that made the craters. Some of the craters around the bottom of the Moon may have ice in them.
There are also darker areas called maria (said "MARR-ee-ah"). These are large pools of lava that cooled a long time ago. Most maria are on the side of the Moon we see from Earth. The lighter areas on the Moon are highlands.
The Moon does not have any atmosphere. It also doesn't have any liquid water on its surface. During the day it becomes very hot, but at night it is icy cold. A person visiting the Moon needs an air supply and a special suit.
The Moon has many craters on its surface. The largest one is called the South Pole-Aitken Basin and is roughly 2500 km across.
We think nearly all the craters on moons or planets were made by huge rocks hitting them a long time ago. They are called impacts.
Some of the craters on the Moon look as if they have rays coming out of them. These rays are rocks thrown across the Moon by the impacts that made the craters. Some of the craters around the bottom of the Moon may have ice in them.
There are also darker areas called maria (said "MARR-ee-ah"). These are large pools of lava that cooled a long time ago. Most maria are on the side of the Moon we see from Earth. The lighter areas on the Moon are highlands.
Earth and Moon
Moon Facts
The Moon is our nearest neighbour in space.
When we look at the Moon from Earth, we always see the same side. Until luna3 sent back photos in 1959, no-one knew what the other side looked like. The Moon is nearly twice as big as the planet Pluto.The "Man in the Moon" isn't always seen as a man. People from India see an old woman with a spinning wheel. People from Mexico see a rabbit!
The Moon is not that small compared to the Earth. Sometimes the Earth and Moon together are called a binary or double planet system.
How big is the moon?
Comparison of the size of the Moon and the Earth
Most of the planets in the Solar System are much bigger than their moons, but the Earth and the Moon are much closer in size. The Moon is just under 3,500 kilometers (km) wide and the Earth is about 12,600 (km). That's only about one third of the size of the Earth as you can see in the picture below. Because of this, the Earth and Moon together are sometimes called a binary or double planet system.
The Moon is our nearest neighbour in space.
When we look at the Moon from Earth, we always see the same side. Until luna3 sent back photos in 1959, no-one knew what the other side looked like. The Moon is nearly twice as big as the planet Pluto.The "Man in the Moon" isn't always seen as a man. People from India see an old woman with a spinning wheel. People from Mexico see a rabbit!
The Moon is not that small compared to the Earth. Sometimes the Earth and Moon together are called a binary or double planet system.
How big is the moon?
Comparison of the size of the Moon and the Earth
Most of the planets in the Solar System are much bigger than their moons, but the Earth and the Moon are much closer in size. The Moon is just under 3,500 kilometers (km) wide and the Earth is about 12,600 (km). That's only about one third of the size of the Earth as you can see in the picture below. Because of this, the Earth and Moon together are sometimes called a binary or double planet system.
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