The sun is by far the largest object inthe solar system. It contains more than99.8% of the total mass of the SolarSystem . The strong gravitational pull of theSun holds Earth and the other planets inthe solar system in orbit. The Sun’s lightand heat influence all of the objects in thesolar system and allow life to exist onEarth.
The Sun is an average star—itssize, age, and temperature fall in aboutthe middle of the ranges of theseproperties for all stars. Astronomersbelieve that the Sun is about 4.6 billionyears old and will keep shining for aboutanother 7 billion years.
Composition of the Sun Abundance Abundance Element (percentage of total (percentage of total number of atoms) mass) Hydrogen 91.2 71.0 Helium 8.7 27.1 Oxygen 0.078 0.97 Carbon 0.043 0.40 Nitrogen 0.0088 0.096 Silicon 0.0045 0.099 Magnesium 0.0038 0.076 Neon 0.0035 0.058 Iron 0.0030 0.14 Sulfur 0.0015 0.040
Solar Winds •expanding atmosphere with a constant flow of tiny, fast, electrically charged particles. •carries remnants of the Sun’s magnetic field, which affect the magnetic fields of the planets and larger satellites. The solar wind pushes the planets’ magnetic fields away from the Sun, turning them into elongated, windsock shapes. •The solar wind spreads out as it leaves the Sun •causes auroras—displays of colored light—in the atmosphere of Earth’s polar regions.
Heliosphere- region through which the solar windblows Within the heliosphere, the Sun providesmost of the heat and light that are present, andthe particles in the solar wind interact with theplanets and satellites in the solar system.
Layers of the Sun
- innermost layer of the sun- it is where the energy that keepsthe sun shining produced-16 million ºC. in a gaseous state.
Solar Envelope - puts pressure on the core and maintains the cores temperature. - The hotter a gas is, the more transparent it is. The solar envelope is cooler and more opaque than the core. It becomes less efficient for energy to move by radiation, and heat energy starts to build up at the outside of the radiative zone.
-is the lowest, densest level of the solar atmosphere.- This is the light we see. That’s why we seethis as the surface. The photosphere is opaque (nottransparent), because it contains negativehydrogen ions (a hydrogen atom with twoelectrons, instead of the usual one). Hydrogenions block, absorb, and emit light, all of whichprevent light from passing directly through acloud of hydrogen ions.
“Sphere of Color” -Very low density -But also very hot - Energy from below excites the atoms and produces emission from this layer. -Predominant element – Hydrogen. -Brightest hydrogen line
A prominence is a feature ofa layer of the Sun’s atmosphere calledthe chromosphere. Magnetic fieldssuspend loops of gas—prominences—above the main photosphere layer.These loops are actually cooler thanthe rest of the photosphere, but theystill appear bright against the dark sky.
Corona -outermost layer of the sun -Only visible during eclipses, it is a low density cloud of plasma with higher transparency than the inner layers. -Its average temperature is 1 million K This picture of the corona was taken during a total solar eclipse on July 11, 1991, in La Paz, Baja California, Mexico.
-cool, dark, temporary patchesSunspot that appear on the outer visible layer (photosphere) of the Sun. Sunspots occur where areas of the Sun’s magnetic field loop up from the Sun’s surface, disrupting the convection of hot gases from below. Sunspots are typically about half the temperature of the surrounding photosphere and so appear darker. -The largest sunspots can be wider than earth.
Importance of the Sun The Sun provides Earth with vast amounts of energy every day. The oceans and seas store Plants use this energy and help keep the Sun’s the temperature of Earth energy to make food, and at a level that allows a plants provide food for life to wide variety of other organisms. exist.
The Sun cannot shine forever, because itwill eventually use up its present fuel. Thenuclear fusion reactions that make the Sun glowdepend on the element hydrogen, but thehydrogen in the Sun’s core will eventually runout. Nuclear reactions have converted about 37percent of the hydrogen originally in the Sun’score into helium. Astronomers estimate that theSun’s core will run out of hydrogen in about 7billion years.
In 3 billion years, the Sun will be hotenough to boil Earth’s oceans away. Four billionyears thereafter, the Sun will have used up all itshydrogen and will balloon into a giant star thatengulfs the planet Mercury. At this point in itslife, the Sun will be a red giant star. The Sun willthen be 2,000 times brighter than it is now, andhot enough to melt Earth’s rocks. At this time theouter solar system will get warmer and morehabitable. The icy moons of the giant planets maywarm enough to be covered by water instead ofice.