The Sun

By Hafsah, Khyati, Amber, Abigail

Contents• Introduction• The Three Layers of The Sun

o The coreo The Radiative layero The Convective layer

• The Three Atmospheric Layerso The Photosphereo The Chromosphereo The Corona

• Sun Spots• Solar Prominences• Solar Flare• Spicules• Fun Facts

Introduction Our star, the Sun, makes up 99% of all the mass

in the Solar System. Its core is so dense and hot that normally repellent nuclei fuse together in nuclear reactions that produce vast amounts of energy. The Sun is mostly hydrogen and helium, and radiates charged particles called solar wind across the Solar System.

The Three Layers of The Sun: The Core

The core starts from the center and extends outward to encompass 25 percent of the sun's radius. Its temperature is greater than 15 million degrees Kelvin. At the core, gravity pulls all of the mass inward and creates an intense pressure. The pressure is high enough to force atoms of hydrogen to come together in nuclear fusion reactions 

The Three Layers of the Sun : The Radiative Layer

The radiative zone extends outward from the core, accounting for 45 percent of the sun's radius. In this zone, the energy from the core is carried outward by photons, or light units. As one photon is made, it travels about 1 millionth of a meter (1 micron) before being absorbed by a gas molecule. Upon absorption, the gas molecule is heated and diffuses another photon of the same wavelength.

The Three Layers of The Sun: The Convective Layer

The convective zone, which is the final 30 percent of the sun's radius. In the convective zone, the energy is transferred much faster than it is in the radiative zone this is because it is transferred through the process of convection.  Hotter gas coming from the radiative zone expands and rises through the convective zone.  It can do this because the convective zone is cooler than the radiative zone and therefore less dense. 

The Three Atmospheric Layers:The Photosphere

The photosphere is the innermost region of the sun's atmosphere and is the region that we can see. "The surface of the sun" typically refers to the photosphere. It is 300-400 kilometers wide and has an average temperature of 5,800 degrees Kelvin. It appears granulated or bubbly, much like the surface of a simmering pot of water. As we pass up through the photosphere, the temperature drops and the gases, because they are cooler, do not emit as much light energy.

The Three Atmospheric Layers:The Chromosphere

The chromosphere extends above the photosphere to about 1,200 miles (2,000 kilometers). The temperature rises across the chromosphere from 4,500 degrees Kelvin to about 10,000 degrees Kelvin. The chromosphere is thought to be heated by convection within the underlying photosphere.

The Three Atmospheric Layers:The Corona

The corona is the final layer of the sun and extends several million miles or kilometers outward from the other spheres. It can be seen best during a solar eclipse and in X-ray images of the sun. Although no one is sure why the corona is so hot, it is thought to be caused by the sun's magnetism. The corona has bright areas (hot) and dark areas called coronal holes. Coronal holes are relatively cool and are thought to be areas where particles of the solar wind escape.

Sun Spots Dark, cool areas called sunspots appear on the

photosphere. Sunspots always appear in pairs and are intense magnetic fields that break through the surface. Field lines leave through one sunspot and re-enter through the other one. The magnetic field is caused by movements of gases in the sun's interior.

Solar Prominences Occasionally, clouds of gases from the chromosphere

rise and orient themselves along the magnetic lines from sunspot pairs. These arches of gas are called solar prominences. Prominences can last two to three months and can extend up to 50,000 kilometers or more above the sun's surface. Upon reaching this height, they can erupt for a few minutes to hours and send large amounts of material racing through the corona and outward into space at 600 miles per second which are called the coronal mass ejections

Solar Flares Sometimes in complex sunspot groups, abrupt,

violent explosions from the sun occur. These are called solar flares. Solar flares are thought to be caused by sudden magnetic field changes in areas where the sun's magnetic field is concentrated.

Spicules As gases churn in the photosphere, they produce

shock waves that heat the surrounding gas and send it piercing through the chromosphere in millions of tiny spikes of hot gas called spicules. Each spicule rises to approximately 3,000 miles above the photosphere and lasts only a few minutes.

Fun Facts !!• The sun rotates on its axis once every 25.38 Earth

days or 609.12 hours.• A person weighing 150 pounds on Earth would weigh

4,200 pounds on the sun because the sun’s gravity is 28 times that of Earth.

• Existing for about 4 and a half billion years, it has burnt up about half of the hydrogen in its core. This leaves the Sun's life expectancy to 5 billion more years.

• Only 55% of all Americans know that the sun is a star.

How is the sun measured??Solar tsunami used to measure Sun’s magnetic fieldA solar tsunami observed by NASA's Solar Dynamics Observatory (SDO) and

the Japanese Hinode spacecraft has been used to provide the first accurate estimates of the Sun's magnetic field.

Solar tsunamis are produced by enormous explosions in the Sun's atmosphere called coronal mass ejections (CMEs). As the CME travels out into space, the tsunami travels across the Sun at speeds of up to 1000 kilometres per second.

Similar to tsunamis on Earth, the shape of solar tsunamis is changed by the environment through which they move. Just as sound travels faster in water than in air, solar tsunamis have a higher speed in regions of stronger magnetic field. This unique feature allowed the team, led by researchers from UCL's Mullard Space Science Laboratory, to measure the Sun's magnetic field.