Unit 2 - Cosmology Part 1: Stars Part 2: Galaxies Part 3: Origin and Evolution of the Universe

Part 1: Stars By the end of Part 1, you should be able to: contrast the life span and energy output of a blue giant star to that of the sun and relate this to the potential existence of life on planets in its orbit. using the Hertzsprung-Russell diagram, classify stars as to their place on the main sequence or in beginning or end points in their life cycles. analyze the various fusion products of a blue giant star over its lifetime, and relate this to the presence and abundance of elements that make up our solar system and its contents, including living organisms.

Part 1: Stars Essential Question: How does the evolution of a star relate to its position on the H-R diagram? Essential Understandings: Stars have a finite lifetime and evolve over time. The mass of a star controls its evolution, lifespan, and ultimate fate. Stars form by condensation and gravitational compression of interstellar gas and dust. The Hertzsprung-Russell diagram illustrates the relationship between the absolute magnitude and the surface temperature of stars. As stars evolve, their position on the Hertzsprung- Russell diagram moves.

What is a star? A star is a large, dense concentration of hydrogen gas Fusion in the core causes two hydrogen atoms to form a helium atom When a star runs out of fuel (hydrogen), it dies A group of stars that form a pattern is called a constellation

Life Cycle Stars follow a definite development and destructions pattern that is referred to as the life cycle of a star

Nebula A star form from a spinning cloud of gas and dust called a nebula Gravity causes the nebula to shrink The spinning nebula flattens into a disk of dust and gas

Protostar A protostar is the material in the center of a nebula that becomes a star As the protostar shrinks, temperature and pressure build up When the temperature and pressure are high enough, the protostar gives off light and hear It is now a star

Main Sequence Star (average star) The most stable phase of stellar life Considered a middle age of the life span A star spends most of the time in this stage The Sun is a main sequence star

Life Span (depends on stars mass) Massive Star (Large Stars) Swell into a supergiant Star will explode into a supernova Remaining matter collapses into an extremely dense ball called a neutron star Eventually becomes a black hole Average Star (Smaller Stars) Swell into red giant Explode into a nova Eventually will collapse into white dwarf or black star

Dwarf Stars White Dwarf Blazing hot Small star Millions of years to cool Black Dwarf Dead Cold star Created when white dwarf cools so it no longer emits heat and light

Hertzprung-Russel Diagram NOT a graph NOT map of where stars are Plots stars based on their temperature, luminosity, magnitude, and mass

H-R Diagram Magnitude – Brightness Luminosity – Energy output of the star per second Temperature – how hot the star is (can also be called spectral class) Mass – how big the star is The most massive stars are the most luminous In the HR diagram, the temperature decreases as one moves to the right.

Part 1 Key Vocabulary Black hole Cosmology Main sequence Nebula

Part 2: Galaxies By the end of Part 2, you should be able to: explain the potential origin and role of ultra massive black holes in the center of galaxies

Part 2: Galaxies Essential Questions: What are the defining characteristics of the three types of galaxies How can large intergalactic distances be measured by using light years? Essential Understandings: The universe is vast in size and very old. The Big Bang theory is our best current model for the origin of the universe. The Big Bang theory states that the universe began in a very hot, dense state that expanded and eventually condensed into galaxies. Galaxies are collections of billions of stars. The basic types of galaxies are spiral, elliptical, and irregular. The solar system is located in the Milky Way galaxy. A light-year is the distance light travels in one year and is the most commonly used measurement for distance in astronomy.

Light Year A light-year is the distance light travels in one year and is the most commonly used measurement for distance in astronomy.

Galaxies Galaxy- huge rotating “disc” of stars, dust, gas, & other debris held together by gravity Made up of billions of stars Estimated there are 1 billion galaxies in the universe Classified by their shape Three kinds: Spiral, Elliptical, Irregular

Spiral Galaxy – The Milky Way Made up of a central core usually contains a supermassive black hole Areas of stars resembling arms coming off of the central core Spiral galaxies have many young stars.

Elliptical Galaxy Have central core, but no arms. Stars are spread out evenly around the core. May be nearly circular or oval in shape. Mostly made of old stars.

Irregular Galaxies No central core No arms No organized shape They tend to be smaller than spirals and elliptical galaxies

Space Radiation All of these things are in the deep reaches of outer space and are too far for us to see them directly. SO HOW DO WE KNOW THEY ARE THERE? All objects in out space emit wavelengths of radiation Electromagnetic Spectrum R O Y G B I V Doppler

Electromagnetic Spectrum Spectroscopy is a technique in which the visible light that comes from objects (like stars and nebulae) is examined to determine the object's composition, temperature, motion, and density. Doppler Effect – change in the wavelength as the emitting object moves closer or farther from the observer.

DOPPLER Blue Shifted – means the wavelengths are being compressed (the slinky is coming together) The object is getting closer to the observer, or wavelength receiver Red Shifted – means the wavelengths are getting elongated (stretching the slinky out) The object is getting further away from the observer or the wavelength receiver. BEST PROOF FOR BIG BANG – expanding universe.

Part 2 Key Vocabulary Electromagnetic spectrum Milky Way Parallax Red Shift

Part 3: Origin and Evolution of the Universe By the end of Part 3, you should be ale to: evaluate the probability of travel to nearby solar systems using current spacecraft speeds.

Part 3: Origin and Evolution of the Universe Essential Questions: How does our current understanding of cosmology support the Big Bang Theory? Essential Understandings: The solar nebular theory is our best current idea for the origin of the solar system. The solar nebular theory explains that the planets formed through the condensing of the solar nebula. Much of our information about our galaxy and the universe comes from ground-based observations across the electromagnetic spectrum. Much information about other planets comes from ground-based observations from Earth, but also from landers and orbiting spacecraft.

The Origin of the Solar System Solar Nebular Theory: Most widely accepted States that the planets were formed in a spinning, condensing cloud of hot gas and dust The planets were formed at around the same time as the sun

The Big Bang Theory The Big Bang theory is our best current model for the origin of the universe. States that the universe began in a very hot, dense state that expanded and eventually condensed into galaxies. Singularity explodes in the Big Bang 13.7 BYA

Future fate of the universe Big Crunch – Universe reverses expansion and shrinks back to a singularity in distant future Infinite Expansion – Universe expands forever. Matter gets too far apart for new stars. Universe goes cold and dark. Big Rip – Expansion of universe gets so fast that atoms cannot hold together. Universe rips apart and all matter becomes energy again, expanding into an infinite void

Part 3 Key Vocabulary Big Bang Theory Light Year Solar Nebular Theory