The solar system formed out of a vast cloud of cold gas and dust called a nebula. All the ingredients for building planets are found in the vast, seemingly empty regions between the stars. But these regions are not really empty – they contain a mixture of gas and dust
The gas and dust in space… The gas is mostly hydrogen and helium The dust is made up of tiny grains of elements such as carbon and iron.
Nebula The dust and gas clump together in huge interstellar clouds called nebulas (or nebulae).
solar nebula The solar nebula is the name of the nebula that formed into our own solar system
Nebulas are so big that it takes light several years to cross them.
These nebulae are cold and dark and are mostly unchanging. Inside of a nebula, gravity and pressure are balanced. Gravity pulls the dust and gas molecules close together to form a cloud Pressure balances with gravity to help keep the cloud from collapsing.
The balance inside of a nebula is unchanging until something (such as a nearby star exploding) upsets the balance, then the nebula begins to collapse inward. When the collapse begins, the stage is set for the formation of a star and planets.
In the middle of the solar nebula contained so much mass and had become so hot that hydrogen fusion began. This created a star that we call the sun.
Bits of dust in the surrounding disk of material stuck together and formed tiny building blocks of planets, called planetesimals. The planetestimals continued to sweep up dust and debris and eventually formed planets.
It took about 10 million years for the solar system to form, and now it is 4.6 billion years old.
The sun is basically a large ball of gas made mostly of hydrogen and helium and held together by gravity. The sun is an average sized star that is close enough to the Earth to give us light and warmth.
Core The center of the sun. This is where the sun’s energy is produced.
radiative zone A very dense region just above the core. The atoms in this zone are so closely packed that light can take millions of years to pass through.
convective zone Gases circulate in convection currents. Hot gases rise from the interior while cooler gases sink toward the interior.
photosphere This is where the gases get thick enough to see. The photosphere is what we know as the visible surface of the sun. It is only about 600 km thick. The photosphere or the visible surface of the sun, is a very dynamic place. As energy from the sun’s interior reaches the surface, it causes the gas to boil and churn, a result of the rising and sinking of gases in the convective zone below.
chromosphere a thin region below the corona. – It’s only 3,000 km thick. Like the corona, the deep, red chromosphere is too faint to see unless there is a total solar eclipse.
corona forms the sun’s outer atmosphere and can extend outward a distance equal to 10-12 times the diameter of the sun. The gases in the corona are so thin that it is visible only during a total solar eclipse.
The sun is formed of six different layers of gas. From the inside out, the layers are the core, radiative zone, convective zone, photosphere, chromospheres, and corona
How can the sun stay hot for so long? And what makes it shine?
Because the sun is so bright and hot, many people thought that it was burning fuel to create energy. But the amount of energy that is released during burning would not be enough to power the sun. If the sun were simply burning, it would only last for 10,000 years.
Scientists began to think that the sun was slowly shrinking due to gravity and that perhaps this would release enough energy to heat the sun. While the release of gravitational energy is more powerful than burning, it is still not enough to power the sun – the sun would only last for 45 million years. This cannot be the explanation.
The sun produces energy in its core by a process called nuclear fusion. Nuclear fusion is the process by which two or more nuclei with small masses (such as hydrogen) join together, or fuse, to form a larger more massive nucleus (such as helium) during this process, energy is produced – a lot of it.
Nuclear fusion reactions, caused by the sun’s massive gravitational field, fuse the sun’s hydrogen into helium. This produces an enormous amount of energy
The energy produced in the core of the sun takes millions of years to reach the sun’s surface. In the radiative zone, the matter is so crowded that the light and energy keep getting blocked and sent off in different directions.
Eventually the energy reaches the convective zone where hot gasses carry it up to the photosphere relatively quickly. From there the energy leaves the sun as light, taking only 8.3 minutes to reach Earth.
The magnetic fields that cause sunspots also cause disturbances in the solar atmosphere. Giant storms on the surface of the sun, called solar flares, have temperatures of up to 5 million degrees Celsius.
Revolve GO AROUND Takes: 365 days -or- 1 year Takes: 365 days -or- 1 year Causes: seasons The Earth also travels around the sun in a path called an orbit. This motion around the sun along its orbit is called revolution. One period of revolution is one year.