Layers of the Sun

The Layers of the Sun:

Core:

The core is the Sun's innermost layer. The core is plasma, a superheated highly ionized gas. It has a temperature of around 15 million degrees Celsius and its pressure is a crushing 260 billion times the earth's atmospheric pressure. This is where all the nuclear reactions take place inside the Sun. These reactions fuse Hydrogen into Helium and let of tremendous amounts of energy in the process. Every second of every day, the Sun converts 700 million tons of Hydrogen into 695 million tons of Helium. The missing 5 million tons is turned into energy and that is A LOT of energy!

Radiative Zone:

The radiative zone is the second layer of the Sun. It has a temperature of about 4 million degrees Celsius. Energy from the core travels through the radiative zone at an extremely slow rate. Photons of light in the radiative zone can only travel a few millimeters before they hit another particle because of the intense density of this layer. The particles are absorbed and then released again. Scientists are still modelling how long it could take a single photon of light to escape the radiative zone. Estimates range from 200 000 years up to as many as 50 million years! Fortunately there are more than just photons of light emitted from the core of the Sun.

Convection Zone:

The convection zone surrounds the radiative zone. In the convection zone, hot material form near the Sun's centre rises. This material then cools at the surface and plunges back down again only to be reheated by the radiative zone and start the cycle all over again. The convection zone works similar to a soup you are boiling on the stove. This "boiling" effect leads to granulation seen on the photosphere.

Photosphere:

The photosphere is the visible surface of the Sun. It is the part we see in the daytime sky. Surprisingly the photosphere is also one of the coolest layers of the Sun. The photosphere is named for the sphere of light as all light we see on Earth during the daytime comes from the photosphere. At this layer, the density of the Sun becomes low enough that light can pass right through it and becomes transparent. From here on out, energy and photons are free to travel out into space

Chromosphere:

The chromosphere lies above the the photosphere as we move outward from the centre of the Sun. It is about 2000 km thick but this is considered a very thin layer of the Sun. The chromosphere is heated by energy from the photosphere. Temperatures range from 4000 to 8000 degrees Celsius. The chromosphere is known as the sphere of colour because it has a red colour to it. It is visible only during a solar eclipse when the photosphere is blocked our or by telescopes using a coronagraph.

Corona:

The corona is the outermost part of the Sun's atmosphere. It is the Sun's halo, or crown. It is also only seen during total solar eclipses or with a coronagraph. The temperature of the corona continues to rise as we move further from the photosphere with temperatures between 1 and 3 million degrees. The corona also extends millions of kilometers into space.

Note:

It is not entirely accurate to say that the Sun is made of gas. It is so hot inside the Sun that the electrons are stripped from their parent atoms in that gas creating what is called a plasma. Sort of like a gas soup of charged particles. Why this is important is because a moving electric charge creates a magnetic field. Since the interior of the Sun is almost all electric charges it can create a massive magnetic field. The convection zone inside the Sun moves the charged particles and that along with the rotation of the Sun on its axis creates rivers of charged particles each generating its own magnetic field. This is why there are so many different field lines on the Sun and we don't see a nice bar magnet like magnetic field that we do with the planets. It is also why the Sun can be so active with sunspots and storms.

Sunspots:

The most noticeable surface feature of the Sun are cooler, darker areas known as sunspots. Sunspots are located where loops of the Sun's magnetic field break through the surface and disrupt the smooth transfer of heat from lower layers of the Sun, making them cooler and darker. Sunspots usually occur in in pairs. One where the loop comes out of the surface and the second where the loop goes back in again. Sunspots last between a few days to a few months. Observing the longer lasting sunspots are what allowed astronomers to determine the rotational period of the Sun. The Sun has a cycle of 11 years where the number of sunspots will increase to a solar maximum and then decrease back down again to a solar minimum. Solar minimum tends to mean few to no sunspot activity, while solar maximum leads to more sunspot activity.

Sunspots:

Solar Flares:

If a loop of the Sun's magnetic field lines get tangled they can actually snap and break, creating a solar flare, which is a violent explosion that releases huge amounts of energy. A big solar flare can release up to 10% of the Sun's energy in a single burst! The solar flare also releases material from the Sun at tremendous speeds and sends it out into space.

Coronal Mass Ejection (CME):

A coronal mass ejection is a large ejection of plasma from the Sun. It works similar to a solar flare but it is on a much larger scale and originates further off the surface of the Sun in the corona. Both solar flares and coronal mass ejections release streams of highly energetic particles that make up the solar wind. These solar storms can be harmful to space technology because they send out large amounts of radiation and charged particles. Fortunately Earth's magnetic field is able to protect us to some extent. Some solar storms have knocked out power grids and disturbed radio, satellite, and cellular communications.

Another highly visible feature on the Sun is a prominence. If plasma flows along a loop of the Sun's magnetic field from sunspot to sunspot, it forms a glowing arch that reaches thousands of kilometers into the Sun's atmosphere. Prominences can last for a day to several months.