chapter 22 the sun and its solar system i. the sun

CHAPTER 22CHAPTER 22THE SUN and ITS SOLAR THE SUN and ITS SOLAR

SYSTEMSYSTEM

I. The SunI. The Sun

Topic 1: Studying the SunTopic 1: Studying the Sun

(a)(a) It is dangerous to look mat the sun because it It is dangerous to look mat the sun because it can cause blindness.can cause blindness.

(b)(b) The telescope was the instrument (by Galileo) The telescope was the instrument (by Galileo) used to make the first scientific observations used to make the first scientific observations of the sun.of the sun.

(c)(c) A A solar telescopesolar telescope is a special telescope that is a special telescope that projects a large image of the sun into a dark projects a large image of the sun into a dark underground room. With special glasses underground room. With special glasses similar to those used by welders, solar similar to those used by welders, solar physicists can safely watch the sun’s image physicists can safely watch the sun’s image and observe changes that occur on the sun’s and observe changes that occur on the sun’s surface.surface.

Topic 1: Studying the SunTopic 1: Studying the Sun(d) Satellites have made it possible to (d) Satellites have made it possible to

study the sun and its radiation without study the sun and its radiation without the interference of Earth’s atmosphere. the interference of Earth’s atmosphere. Orbiting Solar ObservatoriesOrbiting Solar Observatories ((OSO-1 OSO-1 through OSO-8) through OSO-8) returned data from the returned data from the sun from 1962-1979. sun from 1962-1979. Helios AHelios A and and Helios BHelios B were placed in long, oval orbits were placed in long, oval orbits that carried them inside the orbit of that carried them inside the orbit of Mercury. TheMercury. The Solar Maximum SatelliteSolar Maximum Satellite (or (or Solar MaxSolar Max) launched in 1980 ) launched in 1980 functioned until 1989 and functioned until 1989 and Ulysses Ulysses launched in 1990 will fly over the sun’s launched in 1990 will fly over the sun’s pole.pole.

Topic 2: Properties of the SunTopic 2: Properties of the Sun(a)(a) Our sun is an average-sized star. Its Our sun is an average-sized star. Its

diameter of 1 380 000 km is about 110 diameter of 1 380 000 km is about 110 times Earth’s diameter. The sun’s times Earth’s diameter. The sun’s volume could hold more than 1 million volume could hold more than 1 million Earths. Its mass is 745 times greater Earths. Its mass is 745 times greater than all the planets together.than all the planets together.

BACKGROUND:BACKGROUND: For a particle travelling at For a particle travelling at the speed of light, it would take 8 the speed of light, it would take 8 minutes and 20 seconds (on our clock) to minutes and 20 seconds (on our clock) to travel between the sun and Earth.travel between the sun and Earth.

Topic 2: Properties of the SunTopic 2: Properties of the Sun

(b) Temperatures on the sun are (b) Temperatures on the sun are extreme. Its surface temperature is extreme. Its surface temperature is about 5500about 5500ooC and its interior C and its interior temperature may be as high as temperature may be as high as 15 000 00015 000 000ooC.C.

Topic 3: The Sun’s AtmosphereTopic 3: The Sun’s Atmosphere(a) The sun’s atmosphere is divided into three (a) The sun’s atmosphere is divided into three

regions. The regions. The photosphere photosphere is the apparent is the apparent yellow surface of the sun. It is about 400 km yellow surface of the sun. It is about 400 km thick and appears to be made of millions of thick and appears to be made of millions of individual cells, called individual cells, called granules granules about 1500 km about 1500 km across with a bright center and dark edges. across with a bright center and dark edges. Granules are the tops of the columns of gases Granules are the tops of the columns of gases that form in the region below the photosphere. that form in the region below the photosphere. The gases are rising at the centre of the The gases are rising at the centre of the granule and sinking back down at the edges. granule and sinking back down at the edges. Individual granules last about 8 minutes before Individual granules last about 8 minutes before sinking.sinking.

Topic 3: The Sun’s AtmosphereTopic 3: The Sun’s Atmosphere

(a) The photosphere is the lower, (a) The photosphere is the lower, denser (2.8 x 10denser (2.8 x 10-8-8 g/cm g/cm33) part of the ) part of the sun’s atmosphere. sun’s atmosphere. Above the photosphere is the sun’s Above the photosphere is the sun’s outer, less dense atmosphere. At the outer, less dense atmosphere. At the lower part of the outer atmosphere lower part of the outer atmosphere us the us the chromospherechromosphere, colored red , colored red by glowing hydrogen. It extends by glowing hydrogen. It extends thousands of km above the thousands of km above the photosphere.photosphere.


(a) Above the chromosphere is the (a) Above the chromosphere is the coronacorona. It has so little gas that it . It has so little gas that it would be considered a vacuum on would be considered a vacuum on Earth. It surrounds the sun to a Earth. It surrounds the sun to a height of more than 1 million km. It height of more than 1 million km. It is seen during a total eclipse as a is seen during a total eclipse as a faint, pearly light.faint, pearly light.


(b) (b) Solar prominencesSolar prominences are huge, red, are huge, red, flamelike arches of material that flamelike arches of material that occur in the corona. Their light is the occur in the corona. Their light is the result of changes that occur in result of changes that occur in cooler, denser parts of the corona. cooler, denser parts of the corona. They may last for many hours and They may last for many hours and some extend millions of km above some extend millions of km above the photosphere.the photosphere.

Topic 4: SunspotsTopic 4: Sunspots

(a) (a) SunspotsSunspots are dark spots on the are dark spots on the photosphere. Some are barely visible photosphere. Some are barely visible and others are larger than Earth’s and others are larger than Earth’s diameter. Some last a few hours while diameter. Some last a few hours while others remain visible for a few months. others remain visible for a few months. They typically have a dark centre (umbra) They typically have a dark centre (umbra) and a lighter rim (penumbra). and a lighter rim (penumbra).


(a) Sunspots occur in pairs. One is the a (a) Sunspots occur in pairs. One is the a north magnetic pole and the other a north magnetic pole and the other a south magnetic pole. The concentration south magnetic pole. The concentration of magnetic forces at these locations of magnetic forces at these locations slows down solar activity and causes the slows down solar activity and causes the photosphere to cool by as much as photosphere to cool by as much as 15001500ooC.C.


(b) Sunspots appear to move left to (b) Sunspots appear to move left to right across the sun’s surface. This right across the sun’s surface. This motion is caused by the sun’s motion is caused by the sun’s rotation. Since the sun is made of rotation. Since the sun is made of gases, its rotation rate is not gases, its rotation rate is not uniform. At the equator the sun uniform. At the equator the sun takes about 25 Earth days for one takes about 25 Earth days for one rotation and 27 days at the poles.rotation and 27 days at the poles.


(c) The number of sunspots visible on the (c) The number of sunspots visible on the photosphere changes daily. During peak photosphere changes daily. During peak sunspot activity, over 100 may be sunspot activity, over 100 may be counted. During periods of low sunspot counted. During periods of low sunspot activity, several days may pass when no activity, several days may pass when no spots are visible. These changes occur in spots are visible. These changes occur in a a sunspot cyclesunspot cycle that averages about 11 that averages about 11 years from one period of peak activity to years from one period of peak activity to the next.the next.

Topic 5: The Solar Wind and Topic 5: The Solar Wind and Magnetic StormsMagnetic Storms

(a) (a) Solar windSolar wind is the constant stream is the constant stream of electrically charged particles given of electrically charged particles given off by the corona. These particles fly off by the corona. These particles fly into space in all directions, some at into space in all directions, some at an average speed of 400 km/s by the an average speed of 400 km/s by the time they reach Earth. Solar events time they reach Earth. Solar events produce huge gusts of solar wind.produce huge gusts of solar wind.


(b) Great tears, called (b) Great tears, called coronal holescoronal holes, , sometimes appear in the corona. sometimes appear in the corona. Some extend halfway around the Some extend halfway around the sun, and many do not close for many sun, and many do not close for many months. Solar wind pours from months. Solar wind pours from coronal holes in a great torent of coronal holes in a great torent of particles.particles.


(b) (b) Solar flaresSolar flares are another source of are another source of solar wind bursts. They are solar wind bursts. They are outbursts of light that arise suddenly outbursts of light that arise suddenly in areas of sunspot activity. Most in areas of sunspot activity. Most flare up in a few minutes then fade flare up in a few minutes then fade rapidly. The number of solar flares rapidly. The number of solar flares increases as the number of sunspots increases as the number of sunspots increase.increase.


(c) As the solar wind blows past Earth, (c) As the solar wind blows past Earth, some particles interact with Earth’s some particles interact with Earth’s magnetic field and upper magnetic field and upper atmosphere, causing atmosphere, causing aurorasauroras, or , or northern and southern lights. northern and southern lights. Magnetic storms Magnetic storms occur on Earth occur on Earth when the particles thrown out by when the particles thrown out by coronal holes and solar flares are coronal holes and solar flares are added to the constant solar wind added to the constant solar wind produced by the corona.produced by the corona.


(c) At such times auroras may be seen (c) At such times auroras may be seen in middle latitudes as well as in polar in middle latitudes as well as in polar areas, and compass needles may areas, and compass needles may give inaccurate readings. Electrical give inaccurate readings. Electrical surges may disrupt telephone surges may disrupt telephone reception and damage unprotected reception and damage unprotected electrical appliances. Radio electrical appliances. Radio reception in AM, citizen’s band (CB), reception in AM, citizen’s band (CB), and shortwave frequencies may be and shortwave frequencies may be affected.affected.

Topic 6: Source of the Sun’s Topic 6: Source of the Sun’s EnergyEnergy

(a) The sun is mostly hydrogen. Four (a) The sun is mostly hydrogen. Four hydrogen nuclei have a mass of hydrogen nuclei have a mass of 4.030 amu. In fusion 4 hydrogen 4.030 amu. In fusion 4 hydrogen nuclei join to form a helium nucleus nuclei join to form a helium nucleus that has a mass of only about 4.003 that has a mass of only about 4.003 amu. This mass difference is amu. This mass difference is converted into electromagnetic converted into electromagnetic radiation which is transmitted into radiation which is transmitted into space.space.


(a) Astronomers calculate that about 4 (a) Astronomers calculate that about 4 million metric tons of matter are million metric tons of matter are being changed to energy every being changed to energy every second in the sun. 564 million second in the sun. 564 million metric tons of hydrogen becomes metric tons of hydrogen becomes 560 million tons helium.560 million tons helium.


(b) The mass of the sun is so great that (b) The mass of the sun is so great that this process can continue for another this process can continue for another 5 billion years.5 billion years.

chapter 22 the sun and its solar system i. the sun

Documents

suns atmospherea

suns surface

suns outer

suns image

suns pole

suns volume

solar telescope

solar physicists