Astronomy The Solar System, Planetesimals, The Sun, Nuclear Fusion, Planetary Movement

Brainpop: Solar System Brainpop:The Sun

Astronomy  The study of all objects beyond Earth.

The Solar System  The solar system is composed of the sun and the planets and other bodies that travel around the sun.

How did our solar system come to be?

 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.

As a nebula collapses, the dust and gas particles move at a faster rate, increasing the temperature at the center of the cloud.

Collapse of the solar nebula caused heating in the center of the mass and eventually formed the sun.

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

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.

The Structure of the Sun

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 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

Energy Production in the Sun

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.

Review: the structure of an atom

Nuclear Fusion

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.

Activity on the Sun’s Surface

Sunspots are cooler, dark spots on the sun. They are produced by the cooling off of areas in the convective zone due to magnetic fields slowing down the activity in the zone.

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.

Solar flares send out huge streams of particles from the sun. These particles interact with Earth’s upper atmosphere causing spectacular light shows called auroras.

Solar flares can also interrupt radio communications on Earth. They can also affect satellites in orbit.

Solar wind is a continuous stream of energized, charged particles, primarily electrons and protons, flowing outward from the Sun, through the solar system.

This can be very dangerous out in space, but on Earth, our magnetic field repels the electrically charged particles and protects us from solar wind.

Planetary Movement

Rotate SPIN OR TURN Takes: 24 hours -or- one day Causes: day and night Rotation is the spinning on an axis.

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.

Ellipse: the shape of the orbit a planet takes around the sun. Planets move faster in their orbits when they are closer to the sun.