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Bell Ringer: Take out your notebooks and Science fair packets. – Name 5 things that you think are big. Order them from largest to smallest. ** DO NOT use our examples from yesterday;-) While I walk around to check Science fair packets, Each of you should define the following words and give some characteristics of each, using your textbooks. Galaxy: Planet: Star: Solar system: While I walk around to check Science fair packets, Each of you should define the following words and give some examples of each, using your textbooks. Galaxy: a huge group of single stars, star systems, start clusters, dust, and gas bound together by gravity spiral galaxies, elliptical galaxies, irregular galaxies Planet: an object that orbits a star, is large enough to become rounded by its own gravity, and has cleared area of its orbit. Earth, Jupiter, Saturn, Mercury, Venus, Mars Star: giant ball of gas primarily made of helium and hydrogen, which undergoes nuclear fusion sun, polaris, Solar system: a system consisting of the sun and the planets along with other objects that revolve around it. our solar system That’s not THAT Big! Wow! Thinking outside the box and putting things in perspective might help Here’s a little astronomy to help you put this into perspective Earth at Night Hubble’s best This is the Sombraro Galaxie also called M104 in Messier’s catalog at a distance of 28 millions light years. This is considered one of the best pictures Hubble took. A nebula is a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter. Then we have the Ant’s Nebula so called because of its shape and located 3000 and 6000 light years. Then here is the Esquimo Nebula at 5000 light years. In fourth place the Cat’s Eye Nebula. Fifth place the Hour Glass Nebula located 8000 light years the result of an exploding star. In 6th place, we have a part of the Cone Nebula at 2,5 light years In 9th place, two galaxies merging NGC 2207 and IC 2163 located 114 millions light years. Tenth place, a fragment of the Trifid Nebula with many stars at 9000 light years. Voyager 1 Actual position of Voyager 1 (102 AU) Milky Way (our sun is indicated) Distances • The universe is really big • Even small parts are REALLY BIG • Our usual units of distance are simply inadequate (m, km) Then How Do We Do It? • The distance to the Sun is appx. 150,000,000 km • If the Sun were a basketball, Earth would be 110 km away and the size of a BB • The nearest star to us is appx. 40,000,000,000,000 km away • If the entire solar system fit inside a basketball, that star would be over ¾ mile away • The diameter of the Milky Way is appx. 1,240,000,000,000,000,000 km • If the entire solar system fit inside a basketball, our galaxy would stretch for 26,000 miles So How? • We need units MUCH larger to make this easier! • New Unit #1: The Astronomical Unit (AU) • The distance from the Earth to the Sun Appx.150,000,000 km (93 million miles) • The nearest star is 268,170 AU So How? • New Unit #2: The Light Year (ly) • The distance light travels in 1 year • The speed of light is 300,000 km/s (186,000 mi/s) • In one year light can travel 9,500,000,000,000 km! • Nearest star is 4.2 ly away • The Milky Way is appx. 130,000 ly across • We are appx. 27,000 ly away from the center! • Relationship: • 1 ly is appx. 63,000 AU Appx. 150,000 ly Even More! • Voyager 1 - @ 38,000 mph would take 17,500 years to travel 1 ly • Proxima Centari – 4.2 ly away – 73,000 yrs to reach Exit Ticket Why do astronomers use light years instead of kilometers to measure distances in the universe? Bell Ringer: Take out your notebooks. Answer the following question. What have you learned about the universe so far? Galaxies: Galaxy Our solar system is located in the Milky Way Galaxy. A galaxy is a large collection of stars, gas, and dust that is held together by gravity Small galaxies called dwarf galaxies have a million stars. Giant Galaxies, however, can have billions of stars. The Milky way galaxy is a Spiral Galaxy. Spiral galaxies are shaped like Pinwheels. Elliptical Galaxies look like spheres or ovals. Irregular Galaxies appear as splotchy, irregularly shaped “blobs” What keeps it all together? GRAVITY What is Gravity? ??? • Gravity is a force that attracts all objects towards each other. • Newton’s Law of Universal Gravity states that every object in the universe attracts every other object. • The strength of the force between two objects depends on two factors: – The mass of the object – The distance between the objects Gravity, Mass, and Weight • The measure of the force of gravity on an object is called Weight. • Mass doesn’t change!!! • An objects weight can change depending on its location. The Moon has less mass than Earth, so the pull of the moon’s gravity on you would be much less. (about 1/6th ) Gravity and Distance: • The force of gravity decreases as the distance between objects increases. Exit Ticket: • Gravity, Mass, and Distance • Compare and contrast: Draw arrows showing the force of gravity in the second and third pictures.