The Sun Unit 6: Astronomy

First…we have to discuss light Information about universe Light emitted from stars and other bodies in space Electromagnetic spectrum = arrangement of waves according to their wavelengths and frequencies We see visible part of spectrum

Visible Light A range of waves with various wavelengths Passed through a prism Violet bent more than blue Blue bent more than green Etc.

Spectroscopy Study of the properties of light that depend on wavelength absorption spectrum = visible light is passed through a cool gas under low pressure

Absorption Spectrum Each element or compound in gaseous form produces unique set of spectral lines Studying a star Lines indicate which elements --> star’s chemical composition

Remember the Doppler Effect? Light from a source moving away from you appears redder Waves are lengthened Moving toward you appears bluer Waves are shortened Determine whether a star or other body in space is moving away from or toward Earth Measured from the dark lines in spectra and comparing them with a standard spectrum

Intro to the Sun “Average” star Earth’s primary source of energy Only star whose surface we can study Diameter = 109 Earths Mass = 332,000 times of Earth

Our Sun is a Star

Structure of the Sun Sun is made of gas 4 parts No clear boundaries between layers 4 parts Solar interior Photosphere Chromosphere corona

Photosphere Visible surface Radiates most of the sunlight we see Layer of gas Grainy texture --> granules Composition = 90% hydrogen, almost 10% helium Dark lines of absorption spectrum

Chromosphere Above the photosphere Thin layer of hot gases Can see during a total solar eclipse (red rim) Light from photosphere is blocked out

Corona Outermost portion of the solar atmosphere Weak Envelope of gases --> extend a million kilometers from sun

Corona Solar wind = streams of protons and electrons ejected at high speed from the corona Travel through solar system and are lost to space Alters appearance of bodies in the solar system Earth’s magnetic field doesn’t allow them to reach our surface --> do affect our atmosphere

Solar Wind

Sunspots Dark spots on the surface of the sun Temperature is less than the surrounding solar surface Number of sunspots observable vary in an 11-year cycle Increases to maximum (100) --> then decrease to minimum Motion of sunspots --> sun rotates about once a month Not all parts rotate at the same speed (gaseous)

Sunspots

The Solar Cycle

Prominences Concentration of gases often appearing as arches extending beyond corona Sometimes can erupt  matter escapes Sun’s atmosphere

Solar Flares Sudden eruption Above sunspot cluster Release lots of energy (UV, radio, X-ray) Atomic particles released --> reach Earth day later (affect long-distance radio communications) Auroras = bright display of light caused by solar radiation interacting with the upper atmosphere at the poles Following strong solar flare

How Solar Activity Affects the Earth

Solar Interior Source of energy = nuclear fusion Combining of the nuclei of lighter elements to form a heavier element Energy released because some matter is converted to energy

Introduction to Nuclear Energy

Process of nuclear fusion Converts four hydrogen nuclei into the nucleus of a helium atom Lots of energy released! 4 hydrogens = 4.032 amu; 1 helium = 4.003 amu Missing mass! (.029 amu) Animation

Process of nuclear fusion E = mc2 c = speed of light Speed of light is very high (300,000 km/sec) --> amount of energy released from small mass is very high One pinhead of hydrogen to helium > burning thousands of tons of coal

Nuclear Fusion in the Sun Small percentage of hydrogen is converted to energy Helium forms the solar core --> grows

Future of the Sun Will the sun run out of hydrogen fuel? Sun will grow Last another 100 billion years Sun will grow Engulf Earth Sun can exist in its stable state for 10 billion years Already 4.5 billion years old