The Big Bang Galaxies Stars Big Bang theory

The Big Bang, Galaxies, & Stars

Big Bang theory – Origin of the Universe v Big Bang marks the inception of the universe • • Occurred about 13. 7 billion years ago All matter and space was created v Not a huge explosion that hurled matter in all directions. Technically, there was no “bang” v Technically, matter is not moving outward in all directions. Reality: space expands

Big Bang Evidence l 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. l Cosmic Microwave Background Radiation – Penzias & Wilson (1965). Left over radiation from the “explosion”

Raisin bread analogy of an expanding universe

Expansion Evidence for Big Bang l Electromagnetic Energy - Type of energy given off in the form of transverse waves l Different types of electromagnetic energy are distinguished by their different wavelengths

Electromagnetic Spectrum – humans can only see one part of spectrum – visible light

Red Shift – Blue Shift v In 1929, Edwin Hubble observed that spectral lines emitted by stars in distant galaxies were considerably Red shifted. v 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 l The greater the degree of shift of the spectral lines, the faster the object is moving away l The star light DOES NOT appear red or blue (it still appears as white light from the star) l 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 l A GALAXY is a collection of billions of stars held together by gravity l Over l 00 billion galaxies spiral – elliptical - irregular l

Our solar system is part of the spiral Milky Way Galaxy

Edge-on view of the Milk Way Galaxy

Elliptical Galaxy

Spiral galaxy in the constellation Andromeda

Barred Spiral

Understanding Stars Grouping 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 “Hottest” “Coldest” Hydrogen Sodium Hydrogen

Hertzsprung-Russell Diagram Comparing temperature and brightness for various stars

Hertzsprung-Russell Diagram aka Luminosity and Temperature of Stars Diagram – NOT A MAP v DIAGRAM IS A USEFUL WAY TO FOLLOW CHANGES THAT TAKE PLACE AS THE STARS LIVE OUT THEIR LIVES v Diagram is made by plotting (graphing) each star's LUMINOSITY (brightness) and TEMPERATURE (as reflected by color) COMPARED TO THE SUN

Which groups of stars are the

Which group of stars is the HOTTEST?

Which groups of stars are the SMALLEST and DIMMEST?

Schematically, stars fall into regions shown below with respect to the sun.

Star Formation v. A star is born when nuclear fusion starts. v Gravity pulls hydrogen atoms together. As trillions of hydrogen atoms are compressed the temperature increases. v Once the temperature reaches ~15 million ºC, nuclear fusion begins and a star is born.

Life Cycle of Stars – Depends upon their original mass After they spend their life as main sequence star …. l Sun size > expand to red giant in about 5 billion years > white dwarf > black dwarf l Super giant > supernova > very high mass – black hole high mass – neutron star l