The Big Bang, Galaxies, &

Stars

Big Bang theory – Origin of the Big Bang theory – Origin of the UniverseUniverse

Big BangBig Bang marks the inception of the marks the inception of the universe universe • Occurred about 13.7 billion years agoOccurred about 13.7 billion years ago• All matter and space was createdAll matter and space was created

Not a huge explosion that hurled matter Not a huge explosion that hurled matter in all directions. Technically, there was in all directions. Technically, there was no “bang”no “bang”

Technically, matter is not moving outward Technically, matter is not moving outward in all directions. Reality: space expandsin all directions. Reality: space expands

Big Bang EvidenceBig Bang Evidence

Distant galaxies are moving away from Distant galaxies are moving away from each other – Doppler Red Shift. Hubble each other – Doppler Red Shift. Hubble (1929) – the farther away the galaxy is the (1929) – the farther away the galaxy is the faster it is moving away.faster it is moving away.

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

Raisin bread analogy of an Raisin bread analogy of an expanding universeexpanding universe

Expansion Evidence for Big BangExpansion Evidence for Big Bang

Electromagnetic Energy - Type of energy Electromagnetic Energy - Type of energy given off in the form of transverse waves given off in the form of transverse waves

Different types of electromagnetic energy Different types of electromagnetic energy are distinguished by their different are distinguished by their different wavelengthswavelengths

Page 14 of the ESRTPage 14 of the ESRT

Electromagnetic Spectrum – Electromagnetic Spectrum – humans can only see one part of humans can only see one part of

spectrum – visible lightspectrum – visible light

Expansion Evidence Expansion Evidence

Most stars are made of Hydrogen & Most stars are made of Hydrogen & Helium gas. Helium gas.

Elements that emit specific wavelengths Elements that emit specific wavelengths within the electromagnetic spectrum.within the electromagnetic spectrum.

The spectral line pattern can be used to The spectral line pattern can be used to identify the star rather like a fingerprint or identify the star rather like a fingerprint or bar code. bar code.

Red ShiftRed Shift – – Blue ShiftBlue Shift In 1929, Edwin Hubble observed that In 1929, Edwin Hubble observed that

spectral lines emitted by stars in distant spectral lines emitted by stars in distant galaxies were considerably galaxies were considerably Red shifted.Red shifted.

If a galaxy or star were moving toward the If a galaxy or star were moving toward the earth, the spectral lines would show a earth, the spectral lines would show a blue shift.blue shift.

Shifting of Wavelengths is called Shifting of Wavelengths is called the Doppler Effectthe Doppler Effect

• Change in the wavelength Change in the wavelength of light emitted by an object of light emitted by an object due to its motion due to its motion

• Movement toward “squeezes” Movement toward “squeezes” the wavelengththe wavelength

• Shorter wavelengthShorter wavelength• Light shifted toward the blue Light shifted toward the blue

end of the spectrum end of the spectrum

• Movement away stretches the Movement away stretches the wavelength wavelength

• Longer wavelengthLonger wavelength• Light shifted toward the red Light shifted toward the red

end of spectrumend of spectrum

RED SHIFT – RED SHIFT – BLUE SHIFTBLUE SHIFT

The greater the degree of shift of the spectral The greater the degree of shift of the spectral lines, the faster the object is moving awaylines, the faster the object is moving away

The star light DOES NOT appear red or blue (it The star light DOES NOT appear red or blue (it still appears as white light from the star) still appears as white light from the star)

The “bar code” for each element either shifts to The “bar code” for each element either shifts to the shorter wavelength blue end of the spectrum the shorter wavelength blue end of the spectrum or to the longer wavelength red end of the or to the longer wavelength red end of the spectrumspectrum

What is the best inference that can be made concerning the movements of Galaxies A, B, and C?

Structure of the UniverseStructure of the Universe

Hubble Telescope allowed scientists to Hubble Telescope allowed scientists to infer the structure of the universeinfer the structure of the universe

A GALAXY is a collection of billions of A GALAXY is a collection of billions of stars held together by gravitystars held together by gravity

Over l00 billion galaxiesOver l00 billion galaxies

spiral – elliptical - irregularspiral – elliptical - irregular

Our solar system is part of the Our solar system is part of the spiral Milky Way Galaxyspiral Milky Way Galaxy

Edge-on view of the Edge-on view of the Milk Way GalaxyMilk Way Galaxy

Elliptical GalaxyElliptical Galaxy

Spiral galaxy in the constellation Spiral galaxy in the constellation AndromedaAndromeda

Barred Spiral

Understanding StarsUnderstanding Stars

Grouping of stars and the Grouping of stars and the classification system has changed classification system has changed

over time with more advanced over time with more advanced toolstools

STELLAR SPECTRAL STELLAR SPECTRAL CLASSCLASS

Grouping the stars based Grouping the stars based on their temperatureson their temperatures

Hydrogen Hydrogen Hydrogen Sodium

Each class of star has a unique pattern of lines (“bar code”) to identify it.

“Hottest”

“Coldest”

Hertzsprung-Russell Hertzsprung-Russell DiagramDiagram

Comparing temperature and Comparing temperature and brightness for various starsbrightness for various stars

Hertzsprung-Russell Diagram Hertzsprung-Russell Diagram aka Luminosity and Temperature of aka Luminosity and Temperature of

Stars Diagram – NOT A MAPStars Diagram – NOT A MAP DIAGRAM IS A USEFUL WAY TO DIAGRAM IS A USEFUL WAY TO

FOLLOW CHANGES THAT TAKE PLACE FOLLOW CHANGES THAT TAKE PLACE AS THE STARS LIVE OUT THEIR LIVESAS THE STARS LIVE OUT THEIR LIVES

Diagram is made by plotting (graphing) Diagram is made by plotting (graphing) each star's LUMINOSITY (brightness) and each star's LUMINOSITY (brightness) and TEMPERATURE (as reflected by color) TEMPERATURE (as reflected by color) COMPARED TO THE SUNCOMPARED TO THE SUN

Which groups of stars are the BRIGHTEST?

Which group of stars is the HOTTEST?

Which groups of stars are the SMALLEST and DIMMEST?

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

Most stars are on the Most stars are on the Main SequenceMain Sequence because that is where they spend most because that is where they spend most

of their livesof their lives

Our sun is an average main sequence star

Luminosity of 1

Temperature 5500°C – yellow in color

MAIN SEQUENCE

Red Super Giants

Red Giants

White Dwarfs

COLOR AND TEMPERATURE ARE RELATED!

What What color color stars are stars are hottest? hottest? Coldest?Coldest?

Star FormationStar Formation A star is born when nuclear fusion starts. A star is born when nuclear fusion starts.

Gravity pulls hydrogen atoms together. As Gravity pulls hydrogen atoms together. As trillions of hydrogen atoms are trillions of hydrogen atoms are compressed the temperature increases.compressed the temperature increases.

Once the temperature reaches ~15 million Once the temperature reaches ~15 million ºC, nuclear fusion begins and a star is ºC, nuclear fusion begins and a star is born.born.

Stellar Nursery

Space is filled with the stuff to make stars.

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 At 15 million degrees Celsius in the center of the star - nuclear fusion center of the star - nuclear fusion

beginsbegins

Stars start from clouds

Clouds provide the gas and dust from which stars form.

But not this kind of dust

Rather: Irregular Grains Of Carbon or Silicon

A Balancing Act

Energy released from nuclear fusion counter-acts inward force of gravity.

Throughout its life, these two forces determine the stages of a star’s life.

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 Life Cycle of Stars – Depends upon their original masstheir original mass

After they spend their life as main After they spend their life as main sequence star ….sequence star ….

Sun size Sun size >> expand to red giant in about 5 expand to red giant in about 5 billion yearsbillion years > white dwarf > black dwarf > white dwarf > black dwarf

Super giant > supernova > Super giant > supernova >

very high mass – black holevery high mass – black hole

high mass – neutron starhigh mass – neutron star

Star Life Cycle: Stars are like humans. They are born, live and then die.

Nebula – cloud Protostar – new, justNebula – cloud Protostar – new, just

of gas and dust forming starof gas and dust forming star

Main SequenceMain Sequence (like the sun) (like the sun)

Red GiantRed Giant

((Betleguise) – once the Betleguise) – once the star runs out of star runs out of hydrogen and the hydrogen and the balance of forces is balance of forces is upset.upset.

White Dwarf: Smaller stars Supernova: Star that

shrink and cool and has died an explosive

eventually become cold death.

black dwarves.

DEPENDING ON THE ORIGINAL MASSDEPENDING ON THE ORIGINAL MASS

Star Dies – Star casts off shell . It creates nebula that can take a variety of shapes – Ant Nebula

JUST FOR FUNJUST FOR FUN

Validity of the following slides is unknown?Validity of the following slides is unknown?

But it is still cool to imagine the sizes of But it is still cool to imagine the sizes of things in space … things in space …

Terrestrial Planets – Earth largest Terrestrial Planets – Earth largest solid, smaller, densersolid, smaller, denser

Earth compared to Jovian PlanetsEarth compared to Jovian Planetsgaseous, large, low densitygaseous, large, low density

All planets compared to Our SunAll planets compared to Our Sun

No longer considered a planet