Stars Chapter 25

The Sun The Sun’s mass controls the motions of the planets Less dense than Earth High pressure and temperature causes gases to be plasma

Fusion - Combining of nuclei to form a larger nucleusFusion - Combining of nuclei to form a larger nucleus Fission - Separation of large nucleus into smaller nucleiFission - Separation of large nucleus into smaller nuclei The Sun uses fusion to combine Hydrogen into HeliumThe Sun uses fusion to combine Hydrogen into Helium

Anatomy of the Sun Core- The Sun's nuclear "furnace," where fusion reactions initially combine hydrogen atoms to produce helium, yielding energy in the process 1. Core- The Sun's nuclear "furnace," where fusion reactions initially combine hydrogen atoms to produce helium, yielding energy in the process.

Anatomy of the Sun 2. Radiative Zone. Energy moves through a surrounding envelope of gas toward the Sun's surface.

Anatomy of the Sun 3. Convection Zone. Big "bubbles" of hot gas transport energy to the surface.

Solar Zones Radiative Zone- 61% of interior from core. Heat moves directly to the surfaceRadiative Zone- 61% of interior from core. Heat moves directly to the surface Convective Zone- 14% as heat moves to surface and cools, matter becomes more dense and sinks to be reheatedConvective Zone- 14% as heat moves to surface and cools, matter becomes more dense and sinks to be reheated

Anatomy of the Sun 4.Photosphere- The Sun's visible surface. Because of its high temperature, it glows yellow.

Photosphere- lowest layer of the atmospherePhotosphere- lowest layer of the atmosphere 400 Km thick400 Km thick Visible surfaceVisible surface

Chromosphere- second layerChromosphere- second layer 2500 KM thick2500 KM thick 30000° K30000° K Normally not visibleNormally not visible

Anatomy of the Sun 7. Corona- The Sun's outer atmosphere, which is heated by the magnetic field to millions of degrees.

Corona- The outermost layerCorona- The outermost layer Several million kilometers thickSeveral million kilometers thick 1 to 2 million degrees K1 to 2 million degrees K Low densityLow density

Solar Wind Charged particles escaping from the corona Reaches Earth at 400 km/s Particles collide with atmospheric gases to form auroras

Solar Activity Sunspots - Dark colored, cooler spots on the surface of the photosphere; caused by magnetic fields Coronal Holes - Low density gas areas of the corona usually over sunspots; provide escape for solar wind

Solar Activity Solar Flares - Eruptions of particles and radiation from the surface of the Sun; can cause problems with Earth’s communication systems Prominence - An arc of gas that is emitted from the chromosphere or condenses in the corona; 50000° K

Solar Activity Impact Solar activity cycle lasts 22.4 years 11.2 to maximum sunspots 11.2 to minimum sunspots Low sunspot activity cause a cooling of the Earth’s climate (Maunder Minimum)

Spectra Visible light arranged by wavelength Continuous - No breaks in the band Absorption - Bands caused by chemicals in the atmosphere absorbing certain wavelengths Emission - Bright lines from a gas at certain wavelengths

Star Groups Constellations - groups of stars; usually named animals, mythological characters, or everyday objectsConstellations - groups of stars; usually named animals, mythological characters, or everyday objects Circumpolar - Orbit the poles and can be seen year roundCircumpolar - Orbit the poles and can be seen year round Seasonal - Orbit equator and can only be seen during certain times of the yearSeasonal - Orbit equator and can only be seen during certain times of the year

Star Groups Clusters - Group of stars that are gravitationally bound; open or globular Binaries - Two stars gravitationally bound together; appear as one to the human eye. One is brighter than the other

Star Light, Star Bright Apparent Magnitude - The brightness of a star to the naked eye, regardless of distance from Earth.Apparent Magnitude - The brightness of a star to the naked eye, regardless of distance from Earth. Absolute Magnitude - Brightness of stars measured at equal distancesAbsolute Magnitude - Brightness of stars measured at equal distances Luminosity - Amount of energy per second put out by a star.Luminosity - Amount of energy per second put out by a star.

Star Measurement Light Year- The distance the light will travel in a year = X 10¹² km Parsec light years = X 10¹³ km Parallax- Apparent shift in position caused by the motion of the observer

Star Classifications O, B, A, F, G, K, M- Based on spectral lines and temperature O has hottest temperature and fewest lines M has coolest temperature and most lines Each letter is divided into 9 numbered categories

Star Structure 73% Hydrogen 25% Helium 2% Other

Life Cycle Star Formation- Cloud of interstellar gas called a Nebula which forms a ProtostarStar Formation- Cloud of interstellar gas called a Nebula which forms a Protostar Protostar becomes hot enough for fusion to begin and become a starProtostar becomes hot enough for fusion to begin and become a star

Life Cycle Red Giant- Hydrogen is used up and star expands and cools; gases start to escapeRed Giant- Hydrogen is used up and star expands and cools; gases start to escape Core of red giant is hydrogen and convert to carbonCore of red giant is hydrogen and convert to carbon Star shrinks and becomes White DwarfStar shrinks and becomes White Dwarf White Dwarf does not require heat source to continueWhite Dwarf does not require heat source to continue

Life Cycle Neutron Star- Large cores collapse in on themselvesNeutron Star- Large cores collapse in on themselves Supernova- Center of neutron star auses massive explosion blowing off the outer layersSupernova- Center of neutron star auses massive explosion blowing off the outer layers Black Hole- Massive core that collapse in and with a gravitational field that sucks everything in.Black Hole- Massive core that collapse in and with a gravitational field that sucks everything in.