Guided Notes about the SunGuided Notes about the Sun

1.1. The Sun contains more than The Sun contains more than 99 percent99 percent of all the mass in of all the mass in the solar system. The Sun’s the solar system. The Sun’s mass controls themass controls the motions motions of of the the planets and other planets and other objectsobjects..

2. 2. The solar interior is gaseous The solar interior is gaseous throughout because of throughout because of its high its high temperature. temperature. The gases are The gases are completely completely ionizedionized, meaning , meaning that they are composed only of that they are composed only of atomic nuclei and electrons. atomic nuclei and electrons. This state of matter is called This state of matter is called plasmaplasma..

3. 3. The lowest level of the Sun’s The lowest level of the Sun’s atmosphere is the atmosphere is the photospherephotosphere. . This is the This is the visible surfacevisible surface of the of the Sun. Most of the Sun. Most of the lightlight emitted emitted by the Sun comes from this by the Sun comes from this layer.layer.

4. 4. Above the photosphere is the Above the photosphere is the chromospherechromosphere, which is normally , which is normally visible only during a visible only during a solar eclipsesolar eclipse when the photosphere is when the photosphere is blockedblocked. . The chromosphere appears The chromosphere appears redred because it emits most strongly in a because it emits most strongly in a narrow band of red wavelengths.narrow band of red wavelengths.

55. The top layer of the Sun’s . The top layer of the Sun’s atmosphere is the atmosphere is the coronacorona, which , which extends extends several million kilometersseveral million kilometers from the top of the chromosphere. from the top of the chromosphere. The corona is so dim that it can only The corona is so dim that it can only been seen when been seen when the photosphere is the photosphere is blockedblocked, such as during an , such as during an eclipseeclipse..

6. 6. Gas from the corona of the Sun flows Gas from the corona of the Sun flows outward at outward at high speedshigh speeds and forms the and forms the solar windsolar wind. The charged particles are . The charged particles are deflected by the Earth’s deflected by the Earth’s magnetic fieldmagnetic field and form 2 huge rings called the Van and form 2 huge rings called the Van Allen belts. The particles collide with Allen belts. The particles collide with gases in the Earth’s atmosphere, gases in the Earth’s atmosphere, causing them to give off light that we causing them to give off light that we see as see as the aurorathe aurora..

7. 7. The Sun’s magnetic field The Sun’s magnetic field disturbs the solar disturbs the solar atmosphere periodically and atmosphere periodically and causes new features known causes new features known as as sunspotssunspots..

8. 8. Sunspots appear Sunspots appear darkerdarker than the surrounding areas than the surrounding areas on the Sun because on the Sun because they are they are coolercooler. Sunspots typically . Sunspots typically last last two months.two months.

9. 9. Solar flares are Solar flares are violent violent eruptions of particles and eruptions of particles and radiation from the surface of radiation from the surface of the Sunthe Sun. Often, the released . Often, the released particles escape the surface of particles escape the surface of the Sun in the the Sun in the solar windsolar wind and and Earth gets Earth gets bombardedbombarded with with particles a few days laterparticles a few days later..

10.Within the core of the Sun, 10.Within the core of the Sun, where where the pressure and the pressure and temperaturetemperature are extremely are extremely high, fusion occurs. Fusion is high, fusion occurs. Fusion is the combining of lightweight the combining of lightweight nuclei, such as hydrogen, into nuclei, such as hydrogen, into heavier nucleiheavier nuclei..

11.In the core of the Sun, 11.In the core of the Sun, heliumhelium is is a product of the process in a product of the process in which which hydrogenhydrogen nuclei fuse. nuclei fuse. The mass lost in the fusion of The mass lost in the fusion of hydrogen to helium is hydrogen to helium is converted to converted to energyenergy, which , which powers the Sun.powers the Sun.

12. The Sun consists of about 70.4 percent 12. The Sun consists of about 70.4 percent hydrogenhydrogen, and about 28 percent , and about 28 percent heliumhelium, , measured by mass, along with a small measured by mass, along with a small amount of other elements. The Sun’s amount of other elements. The Sun’s composition represents that of the composition represents that of the galaxy as a wholegalaxy as a whole. Hydrogen and helium . Hydrogen and helium are the predominant gases in are the predominant gases in starsstars, as , as well as in the entire well as in the entire universeuniverse. All other . All other elements are in very small elements are in very small proportions proportions compared to hydrogen and helium.compared to hydrogen and helium.