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The Big Bang, Galaxies, & Stars. Big Bang theory – Origin of the Universe. Big Bang marks the inception of the universe Occurred about 13.7 billion years ago All matter and space was created Not a huge explosion that hurled matter in all directions. Technically, there was no “bang”
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Big Bang theory – Origin of the Universe • Big Bangmarks the inception of the universe • Occurred about 13.7 billion years ago • All matter and space was created • Not a huge explosion that hurled matter in all directions. Technically, there was no “bang” • Technically, matter is not moving outward in all directions. Reality: space expands
Big Bang Evidence • Distant galaxies are moving away from each other – Doppler Red Shift. Hubble (1929) – the farther away the galaxy is the faster it is moving away. • Cosmic Microwave Background Radiation – Penzias & Wilson (1965). Left over radiation from the “explosion”
Expansion Evidence for Big Bang • Electromagnetic Energy - Type of energy given off in the form of transverse waves • Different types of electromagnetic energy are distinguished by their different wavelengths
Electromagnetic Spectrum – humans can only see one part of spectrum – visible light
Expansion Evidence • Most stars are made of Hydrogen & Helium gas. • Elements that emit specific wavelengths within the electromagnetic spectrum. • The spectral line pattern can be used to identify the star rather like a fingerprint or bar code.
Red Shift – Blue Shift • In 1929, Edwin Hubble observed that spectral lines emitted by stars in distant galaxies were considerably Red shifted. • If a galaxy or star were moving toward the earth, the spectral lines would show a blue shift.
Shifting of Wavelengths is called the Doppler Effect • Change in the wavelength of light emitted by an object due to its motion • Movement toward “squeezes” the wavelength • Shorter wavelength • Light shifted toward the blue end of the spectrum • Movement away stretches the wavelength • Longer wavelength • Light shifted toward the red end of spectrum
RED SHIFT – BLUE SHIFT • The greater the degree of shift of the spectral lines, the faster the object is moving away • The star light DOES NOT appear red or blue (it still appears as white light from the star) • The “bar code” for each element either shifts to the shorter wavelength blue end of the spectrum or to the longer wavelength red end of the spectrum
What is the best inference that can be made concerning the movements of Galaxies A, B, and C?
Structure of the Universe • Hubble Telescope allowed scientists to infer the structure of the universe • A GALAXY is a collection of billions of stars held together by gravity • Over l00 billion galaxies spiral – elliptical - irregular
Understanding StarsGrouping of stars and the classification system has changed over time with more advanced tools
STELLAR SPECTRAL CLASS Grouping the stars based on their temperatures
Each class of star has a unique pattern of lines (“bar code”) to identify it. Hydrogen Hydrogen Hydrogen Sodium “Hottest” “Coldest”
Hertzsprung-Russell Diagram Comparing temperature and brightness for various stars
Hertzsprung-Russell Diagram aka Luminosity and Temperature of Stars Diagram – NOT A MAP • DIAGRAM IS A USEFUL WAY TO FOLLOW CHANGES THAT TAKE PLACE AS THE STARS LIVE OUT THEIR LIVES • Diagram is made by plotting (graphing) each star's LUMINOSITY (brightness) and TEMPERATURE (as reflected by color) COMPARED TO THE SUN
Schematically, stars fall into regions shown below with respect to the sun.
Most stars are on the Main Sequence because that is where they spend most of their lives Our sun is an average main sequence star Luminosity of 1 Temperature 5500°C – yellow in color
What color stars are hottest? Coldest? Red Super Giants Red Giants MAIN SEQUENCE COLOR AND TEMPERATURE ARE RELATED! White Dwarfs
Star Formation • A star is born when nuclear fusion starts. • Gravity pulls hydrogen atoms together. As trillions of hydrogen atoms are compressed the temperature increases. • Once the temperature reaches ~15 million ºC, nuclear fusion begins and a star is born.
Space is filled with the stuff to make stars – mostly hydrogen gas. Image of the pillars of creation inside the crab nebula
At 15 million degrees Celsius in the center of the star - nuclear fusion begins
As long as the forces of gravity and thermal pressure are balanced, the star exists on the main sequence.
Life Cycle of Stars – Depends upon their original mass • After they spend their life as main sequence star …. • Sun size > expand to red giant in about 5 billion years > white dwarf > black dwarf • Super giant > supernova > very high mass – black hole high mass – neutron star
Star Life Cycle: Stars are like humans. They are born, live and then die. • Nebula – cloud Protostar – new, just of gas and dust forming star
Red Giant (Betleguise) – once the star runs out of hydrogen and the balance of forces is upset. Main Sequence(like the sun)
DEPENDING ON THE ORIGINAL MASS White Dwarf: Smaller stars Supernova: Star that shrink and cool and has died an explosive eventually become cold death. black dwarves.
Star Dies – Star casts off shell . It creates nebula that can take a variety of shapes – Ant Nebula
JUST FOR FUN Validity of the following slides is unknown? But it is still cool to imagine the sizes of things in space …
