The Universe planets planets moons moons stars stars solar systems solar systems galaxies galaxies nebulae nebulae empty space empty space more? more?

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The Universe

The UniverseThe Universeplanetsmoonsstarssolar systemsgalaxiesnebulaeempty spacemore?Whats in it?2In regards to the MORE bullet, the vast majority of the universe is made of stuff we cannot see. Very interesting information about What the Universe is Made of can be found on NASAs WMAP Universe web site (http://map.gsfc.nasa.gov/universe/uni_matter.html). According to this site, only about 5% of the universe is made of normal stuff like atoms.UniverseNebulaeGalaxiesSolar SystemsStar(s)PlanetMoonsWhats wrong with this model of the universe?It is not to scale.3This is a visual representation of how the universe can be organized. Nebulae can exist outside of galaxies, yet nebulae tend to be the birthplace of stars and other celestial materials. Galaxies overlap the nebulae because galaxies are large collections of stars and many of those stars may come from the same nebula.

Interstellar cloud of dust and gassesBirthplace of starsNebulae4This is a Hubble Telescope photo of the Horsehead Nebulae. Part of the Orion constellation, The Horsehead Nebula as the name says looks like a horses head but it is beautiful nonetheless. It is actually a dark cloud of gas and dust. Using Orion's belt, we can locate Sirius, the brightest star in the sky. The Horsehead Nebula is approximately 1500 light years from Earth. It is one of the most identifiable nebulae because of the shape of its swirling cloud of dark dust and gases, which is similar to that of a horse's head when viewed from Earth. The shape was first noticed in 1888 by Williamina Fleming on photographic plate B2312 taken at the Harvard College Observatory.

NOTE: Background information from Journey Through the Galaxy (http://burro.astr.cwru.edu/stu/stars_birth.html).Nebulae and Stellar BirthOverviewStellar nurseries are made of clouds of dust and gas called nebulae (singular is nebula). All stars are born out of nebulae -- except in some rare instances when two neutron stars merge to form a black hole (however, both neutron stars and black holes are considered to be "dead" stars).There are two different origins of nebulae. The first origin for material is the universe's creation itself: Soon after its birth, atoms were created in the universe, and it is from these that the first dust and gas clouds formed. This means that the gas and dust that make up this type of nebula were not created in a star, but are the original matter from the beginnings of the universe. The second kind of nebulae are produced by the supernovas of exploding stars. The matter ejected from them created the Veil and Crab nebulae, as well as many more. Also, keep in mind that the origins of nebulae are not as clear cut as this; a nebula can be a mixture of primordial material as well as new material from previous stars.

Galaxiescollection of stars, gas & dust held together by gravity

millions of galaxies are known to existgalaxies can contain from hundreds of thousands to one trillion stars3 major types5The image is taken by the Hubble Space Telescope is of the Sombrero Galaxy: It is spiral unbarred galaxy with a brilliant white core surrounded by dust with a diameter of 50,000 light-years and is 28 million light years away from our home, Earth. Situated in Virgo constellation, although it can be seen easily through small telescopes.

Spiral galaxies spiral arms made of stars barred spiral - has two or more long arms extending away from the central bar cluster of starsElliptical galaxies no spiral arms and no flattened disk (think football)Irregular galaxieshave no regular shapeGalaxies: The Three Types6Pictures pop up with text to help visualize each type of galaxy.

More detailed background information about all the galaxy types can be found at http://seds.org/messier/galaxy.html (SEDS web site).

Milky Way Spiral galaxy (Barred-Spiral)100,000 light-years in diameter. contains about 200 billion starsHome to Our Sunthe Sun and Earth are located 2/3 away from center in one of the outer spiral armsSun orbits central Milky Way at about 235 km/s around the center of the galaxyYou are here!7The term light-year will be discussed in depth in a later slide.

NOTE: The image of the spiral galaxy is a close approximation as to what our galaxy would look like from an outsider. The arrow points to our solar system approximate location 2/3 distance out from galactic core.

Andromeda Galaxynearest galaxy neighborabout 2.5 million light years away120,000 light years wideA spiral galaxyThe largest galaxy in our local group of galaxies8This is the Andromeda Galaxy and is similar to our Milky Way. It is the nearest spiral galaxy to us.

The Andromeda Galaxy is a spiral galaxy approximately 2,500,000 ly away in the constellation Andromeda. It is one of the farthest objects visible to the naked eye, and can be seen even from urban areas with binoculars. It is the largest galaxy in our local group of about 33 galaxies.So Where Did It All Come From?Scientifically believed origins:Big BangOscillating UniverseGeocentric ModelHeliocentric Model

Big BangThe universe was created from one, instantaneous, large explosion outwardmost widely scientific accepted theory of the origin of the universeOscillating Universestates that the universe grows outward until gravity pulls it back to the center and then expands outward over and over again Geocentric Modelstates all celestial bodies orbit the Earth

Heliocentric Modelstates all objects in our solar system circle the Sun.