Sun and Stars - SOL Review Zone€¦ · Sun and Stars October 04, 2016 •More massive stars (larger than the sun) begin in much the same way as the sun but end very differently-can

Sun and Stars October 04, 2016

The Sun

Properties of the Sunlargest object in the solar system in size and mass (10 Jupiters lined edge to edge across sun)

contains more than 99% of all the mass in the solar system (1048 time the mass of Jupiter)

solar interior is ionized gas...a state of matter known as plasma



Sun's Atmosphere

• Photosphere: lowest layer of the atmospherevisible surface of sun Photo means "light"6000 0K (10,000 0F)

• Chromosphere: layer above the photosphere; 30,000 0K (54,000 0F)> Chroma means "color"

• Corona: top layer of the sun's atmosphereonly visible during an eclipsetemps range from 1 to 2 million 0K


• Solar Wind: A wind of charged particles flowing outward throughout the solar system

particles are deflected by Earth's magnetic field in 2 huge rings known as the Van Allen Radiation Beltsaffects all the planets


• Sunspots: dark spots on the surface of the photosphere

• are actually very bright but appear dark because they are cooler than the surrounding area of the sun

• found where the sun's magnetic field pokes through the photosphere

Solar Activity


The Solar Interior• Core of sun has high pressure and high temperatures causing fusion to occur• Hydrogen nuclei are fused into helium • Matter is converted into energy.(Einstein's theory of relativity E=mc 2)• Powers the sun

• Check Point

Describe the process that powers the sun.


Solar Composition

• 73.4% hydrogen• 25% helium• other trace elements such as C, N, O, Ne, Mg, Si, S, Ca, Fe• similar make up in other stars

Predominant make up in stars and the universe

Life Cycle of Stars• All stars have a similar formation starting with a nebula• The nebula begins to collapse on itself, begins rotating, and forms a disk with a condensed center object (protostar)• Eventually fusion begins when the temperature is hot enough


• Stars like the sun have a main sequence life span of 10 billion years• Once all the hydrogen fuel is gone, the sun will become a red giant

-loses gases from its outer layers because the star is so large and the surface of gravity is so low-if the core becomes hot enough again, fusion will begin where helium is converted to carbon-if the core does not become hot enough the red giant loses more of its gaseous outer layers--the shell gases are known as planetary nebula-core of the star becomes exposed and is a white dwarf

-is stable because of pressure-will eventually become a black dwarf


• More massive stars (larger than the sun) begin in much the same way as the sun but end very differently

-can become a red giant several times before becoming a white dwarf-if the star does not become a white dwarf because it did not lose enough mass, then the core becomes too massive (the electrons and protons in the core merge to form neutrons) creating a neutron star

• A neutron star forms while the star is still collapsing, the outer gasses fall inward and hit the solid core which causes a supernova

-this explosion creates elements heavier than Fe (iron)


• Some stars are so massive they continue to collapse forever where light can't even escape-creates a black hole



Stellar Positions and Distances

• Astronomers use two basic units of measure for long distances

-a light year is the distance light travels in one year=9.461 X 1012km-a larger unit is the parsec=3.27 light years or 3.086 X 1013km

• The apparent shift in position caused by the motion of the observer is known as parallax (change in position of earth as it orbits the sun)

-the closer the star-the larger the shift in parallax-the farther the star- the smaller the shift in parallax-distance can be estimated in parallax shift

• Apparent Magnitude: ancient Greek classification-how bright a star appears to be

-modern system includes objects brighter and fainter than the Greek System-the very brightest objects have a negative number

• Absolute Magnitude: is the brightness an object would have if it were placed at a distance of 10 parsecs

-allows comparisons that are based on how bright the stars would appear at equal distances from an observer-disadvantage: can only be calculated when actual distance is known


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Sun and Stars - SOL Review Zone€¦ · Sun and Stars October 04, 2016 •More massive stars (larger than the sun) begin in much the same way as the sun but end very differently-can