sun
TRANSCRIPT
Sun
Introduction and General Properties
Sun is a typical star.
Stars are balls of hot gases.
Mass= 330,000 x Earth
Volume= 1 million x Earth
Surface gravity= 28 x Earth
Luminosity= 4 x 1026 watts
Surface temperature= 5780 K
Core temperature= 15 million K
Composition:75%25%2%
Differential rotation:30 days at equator30 days near poles
D:\Exploring the Sun.mp4The Sun Videos\Fantastic Aurora- Inside the Sun to Earth's Poles.mp4
The Sun Videos\Inside our Sun a deeper look.mp4
The Sun's Energy Source CORONA• Fortunately for life on earth, the Sun's energy output is just about constant so
we do not see much change in its brightness or the heat it gives off.
• more than 15 million degrees Kelvin
• and the material in the core is very tightly packed or dense.
• An atom is constructed of protons, electrons and neutrons.
• Neutrons have no electric charge and therefore do not interact much with the surrounding medium.
• The protons, which have positive electric charge,
• and the electrons, which have negative electric charge, remain in the core and drive the reactions which fuel the Sun.
• The charge neutral material of protons and electrons that makes up the core is called plasma.
• This motion, combined with the high density of the plasma, causes the particles to continuously slam into one another creating nuclear reactions. It is the fusion, or slamming together, of particular combinations of particles that provides the energy source of the Sun.
A Slow Means of Energy Transport Radiation Zone
• The physical transport of energy from its production site to the surrounding regions can be done in a number of ways.
• . However, for a star like the Sun, the most efficient means of transferring energy near the core is by radiation.
• Consequently, the region surrounding the core of the Sun is known as the radiation zone.
• Throughout this region of the solar interior, energy, in the form of radiation, is transferred by its interaction with the surrounding atoms.
• In the radiation zone of the Sun the temperature is a little cooler than the core and as a result some atoms are able to remain intact.
• As an illustration, imagine standing in a crowded gymnasium with each person holding an empty glass. There is a sink on one end of the gym and someone at the opposite end wants a drink, but because the gym is so crowded no one can move. The person nearest the sink can fill their glass with water and pour it into the glass next to them. This process could continue until the water is passed across the gym.
The "Boiling" Zone Convection Zone• This new method of transport is required because outside of the radiation zone the temperature is
relatively cool, now only 2 million degrees Kelvin as opposed to 5 million in the radiation zone.
• The most efficient means of energy transfer is now convection and we find ourselves in the region of the Sun's interior known as the convection zone.
• The hotter material near the top of the radiation zone (the bottom of the convection zone) rises up and the cooler material sinks to the bottom.
The Sun's "Effective" Surface Photosphere• The core, the radiation and the convection zones make up the interior of the
Sun, all of which is invisible to conventional means of observation.• Much like earth scientists study the interior of the earth by measuring
different vibrations, solar scientists are able to study the interior of the Sun using its natural oscillations.
• This new field of solar study is known as helioseismology.
• The exterior of the Sun is comprised of the surface and the atmosphere, both of which can be studied using an array of telescopes and radiation detectors.
• The photosphere is called the apparent surface of the Sun. • Because the Sun is completely made of gas there is no hard surface like there
is on earth. • . The photosphere is the disk you see in the sky when you look at the Sun
through a filtered telescope or as a projection on a piece of paper.
Shown here is an image of granulation around a Sunspot in the photosphere.
• When you look at the Sun with a filtered telescope you can see evidence in the photosphere of the convective bubbles in the convection zone below.
• The continuous rising and falling of hot and cool bubbles produces a pattern on the surface of the Sun that is referred to as granulation.
• Energy is transported through the photosphere once again by radiation.• Although the temperature of the photosphere is cool, about 5800 degrees
Kelvin,• the gas is thin enough that the atoms absorb and release energy.• In fact, most of the light that we receive from the Sun on earth is energy that
was released by atoms in the photosphere (which literally means sphere of light).
• It takes light from the Sun just over eight minutes to reach the earth.
A "Dancing" Layer of the Sun Chromosphere
• Above the photosphere is a layer of gas, approximately 2000 km thick, known as the chromosphere or sphere of color.
• The chromosphere is most easily viewed by filtering out all other wavelengths of light from the Sun and only letting the red light from the chromosphere through.
• Views of the chromosphere show convective cell patterns similar to those in the photosphere, but much larger.
• This large scale convection is known as super-granulation.
• Another interesting feature of the chromosphere is its jagged outer layer which is constantly changing
• The motion is much like flames shooting up several thousands of kilometers and then falling again.
• These spiky, dancing flames are called spicules and can be seen in the image to the right.
Things are heating up again Transition Region
• It gets its name from the crown like appearance evident during a total solar eclipse.
• The corona stretches far out into space and, in fact, particles from the corona reach the earth's orbit.
• The corona is very thin and faint and therefore can only be seen from earth during a total solar eclipse or by using a coronagraph telescope which simulates an eclipse by covering the bright solar disk.
• The shape of the corona is mostly determined by the magnetic field of the Sun.
Below is an image of a solar prominence taken by the Soft X-ray Telescope on the Yohkoh satellite currently orbiting the earth.
• These magnetic structures can be seen extending up into the corona.
• As particles follow the path created by the magnetic field they form dynamic loops and arches that are most readily visible with special telescopes.
• These structures are known as solar prominences.
• This "solar wind" transports particles through space at 400 kilometers per second.
• Atoms in the earth's atmosphere interact with these high energy particles by accepting energy from them and then releasing that energy in the form of colored light.
• This display of light is known as the Aurora Borealis when it occurs in the northern hemisphere.
• The short wavelength X-rays do not make it through the earth's atmosphere so X-ray images of the corona must be taken above our atmosphere from telescopes in space.
• Soft X-ray images of the corona are taken by a telescope on the Yohkoh satellite mentioned above.
• (X-rays come in a wide range of energies. Soft X-rays are at the lower end of the energy range and the term hard X-rays is given to those at the higher end.)
• By viewing the Sun with many different instruments, each tuned to a particular wavelength of the Sun's energy, scientists can use their "different eyes" to help look for answers to the many questions that still surround our nearest star.
A Look Inside Our Nearest Star!