The Universe Stars Our Solar System Orbits Gravity Astronomy The Universe Stars Our Solar System Orbits Gravity 20 April 2017

The Size of the Universe Distance in space is often measured in light years One light year is the distance that light travels in one Earth year Our moon is 1 1/2 light second away Our sun is 8 light minutes away Our closest star (besides the sun) is 4 light years away The universe is thought to be 25 billion light years across! 20 April 2017

Origin of the Universe Big bang Approximately 15 billion years ago Started from a single point and has been spreading outward ever since 20 April 2017

Raisin bread analogy of an expanding universe 20 April 2017

Organization of the Universe Galaxy Cluster Galaxy (ex. Milky Way) Solar System Star (Sun) Planet (Earth) 20 April 2017

Galaxies A huge cluster of stars and other matter is called a Galaxy Move Rotate in place (spin) Move away from the center of the universe Have different shapes Spiral, like the Milky Way Globular Ring 20 April 2017

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 20 April 2017

Page 14 of the ESRT 20 April 2017

Electromagnetic Spectrum – humans can only see one part of spectrum – visible light 20 April 2017

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. 20 April 2017

4/20/2017 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. When scientists look at the spectrum of radiation emitted by stars in far away galaxies they noticed the positions of the characteristic wavelengths are shifted to the shorter (blue light end of spectrum) or longer (red light end of spectrum) wavelengths depending on whether the star is coming towards you or moving away. In 1929, Edwin Hubble observed that spectral lines emitted by stars in distant galaxies were considerably Red shifted. 20 April 2017 ©1999 John Culpepper

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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 20 April 2017

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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 20 April 2017

What is the best inference that can be made concerning the movements of Galaxies A, B, and C? 20 April 2017

Hubble Telescope and Deep Space The Hubble Telescope was pointed at an area of “nothing” The next slide is the image Hubble captured. Each bright spot is a galaxy, similar to our own Milky Way 20 April 2017

Hubble Deep Space Galaxies 20 April 2017

Inferences about our Galaxy Large (as galaxies go): 100,000 ly across Contains several hundred billion stars The Milky Way rotates once every 220 million years That means we are moving at 250 km per second!! 20 April 2017

The Milky Way: our galaxy 20 April 2017

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Our solar system is part of the spiral Milky Way Galaxy 20 April 2017

Edge-on view of the Milk Way Galaxy 20 April 2017

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Elliptical Galaxy 20 April 2017

Spiral galaxy in the constellation Andromeda 20 April 2017

Barred Spiral 20 April 2017

Our Solar System in the Milky Way: Is located in an arm on the outer edge of the Milky Way We face in to the center of the galaxy in the winter This is why the Milky Way is brighter in the winter time 20 April 2017

Stars Fueled by nuclear fusion Our closest star is the Sun When atoms are compressed so hard they “fuse” Creates a tremendous amount of energy Our closest star is the Sun 20 April 2017

Stars Stars are born, live and die Classified based on size and temperature What they become in death can be determined by the Hertzsprung-Russell Diagram (H-R Diagram) 20 April 2017

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Which groups of stars are the BRIGHTEST? 20 April 2017

Which group of stars is the HOTTEST? 20 April 2017

Which groups of stars are the SMALLEST and DIMMEST? 20 April 2017

Our Sun A medium sized star Makes up 99.86% of the Sloar System’s mass! Contains sunspots Storms within the hot gas Appear as black spots that move across the surface Are produced in cycles 20 April 2017

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Satellites Any object that orbits another object in space is known as a satellite Planets are natural satellites of their stars Moons are natural satellites of their planets We also have artificial satellites which orbit Earth 20 April 2017

Our Solar System The Sun is near the center of the Solar System Satellites in the Solar System: Rocky planets Like your home planet Gas giants Solid core surrounded by gas Other stuff Asteroids, meteors and comets 20 April 2017

The Planets: Two kinds Rocky (Terrestrial) Gas Giants Mercury Venus Earth Mars Pluto Gas Giants Jupiter Saturn Uranus Neptune Saturn would float if you could put it in water! 20 April 2017

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The Big “E” Earth is unique Due to abundant liquid water Means life as we know it! 20 April 2017

Home! 20 April 2017

Other Natural Satellites Asteroids Chunks of rock and metal that circle the sun Range in size from hundreds of km to mm Most are in a belt between Mars and Jupiter Rarely cross Earth’s orbit May have caused the extinction of dinosaurs 20 April 2017

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Other Natural Satellites Comets “Dirty snowballs” from outside the solar system Probably provided young Earth’s water “Tail” created by vaporization when they approach the Sun Examples: Halley’s – 76 year orbit (will be back in 2061) Hale-Bopp – was near in 1997 (will be back in ???) 20 April 2017

Comet Hale-Bopp 20 April 2017

Other Natural Satellites Meteors Small particles pulled into Atmosphere by Earth’s gravity Most burn up in the atmosphere Shooting stars If they reach the Earth’s surface are called meteorites Evidence of meteors: Most is eroded away Meteor Crater in Winslow AZ 20 April 2017

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Terrestrial Planets – Earth largest solid, smaller, denser 20 April 2017

Earth compared to Jovian Planets gaseous, large, low density 20 April 2017

All planets compared to Our Sun No longer considered a planet 20 April 2017

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Kepler’s Three Laws of Planetary Motions Planets’ orbits’ are elliptical in shape A planet will move through equal area of space in an equal amount of time The farther a planet is from the focus, the longer the period of revolution 20 April 2017

Kepler’s First Law The orbits of planets around stars is elliptical 20 April 2017

Geometry of Orbits The orbits of planets around their star are elliptical with the star at one focus and the planet’s average mass at the other focus 20 April 2017

Geometry of Orbits The major axis is defined by a line that passes through the two foci (plural of focus) 20 April 2017

Geometry of Orbits The word eccentricity is used to describe how “out of round” an orbit is Eccentricity can be defined numerically No units are used in describing eccentricity 20 April 2017

SHAPE OF ELLIPSES Eccentricity = 0 circle Eccentricity = 0.5 Eccentricity = 1 line 20 April 2017

Kepler’s Three Empirical Laws of Planetary Motion 1. The orbital paths of the planets are elliptical, with the Sun at one focus 20 April 2017

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Kepler’s Three Empirical Laws of Planetary Motion 2. An imaginary line connecting the Sun to any planet sweeps out equal areas in equal time.. Area 1 Area 2 20 April 2017

TO THE HUMAN EYE, MOST ORBITS OF PLANETS LOOK LIKE CIRCLES SLIGHTLY ELLIPTICAL SHAPE OF EARTH’S ORBIT CAUSES THE PLANET TO VARY THE DISTANCE TO THE SUN DURING REVOLUTION 147 million kms. 152 million kms.

This is the best website for 1st and 2nd laws of Kepler https://solarsystem.colorado.edu/home/lowRes.html 20 April 2017

Geometry of Orbits The formula for finding eccentricity is: Distance between the foci Eccentricity = Length of the major axis This formula is found in your ESRTs ***Units must be the same in the numerator and denominator, then the units cancel and eccentricity is expressed without units. 20 April 2017

Eccentricity Example The distance between foci of planet beta’s orbit is 3000 km. The length of it’s major axis is 600,000 km. What is the eccentricity of Beta’s orbit? 20 April 2017

 Which has a more eccentric orbit, the comet or Beta? Eccentricity Example  A comet has a major axis with length 12,000,000 km and foci that are 24,000 km apart. What is the eccentricity of the comet’s orbit?  Which has a more eccentric orbit, the comet or Beta? 20 April 2017

The Force of Gravity Earth’s orbit around the sun has an eccentricity of 0.017 (close to zero) Therefore the distance between the sun and Earth changes very little throughout the year  What is the difference in distance between the Earth’s nearest approach and farthest distance from the sun? 20 April 2017

Kepler’s Second Law: The Force of Gravity The speed of a planet varies with its distance from the sun The closer to the sun, the faster the planet travels in its revolution around the sun 20 April 2017

Equal Area, Equal Time 20 April 2017

Kepler’s Third Law in our Solar System Use your ESRT to complete the chart below: Planet Distance from Sun Period of Revolution Mercury Earth Mars Saturn Uranus Pluto 20 April 2017

Orbits in our Solar System 20 April 2017