Solar system Stars and Galaxies

Transcription

1 5/18/16 Solar system Stars and Solar system, stars and galaxies The life cycle of stars inner planets/outer planets nebular theory novae and supernovae gravita>onal contrac>on white dwarf and black holes thermal fusion thermal pressure solar wind nebular theory these stars only a few million years old nebular theory Nova Origins 1. A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other gases. 2. Gravity pulls gases and dust together. 3. When enough mass gathers, the force of gravity starts to fuse hydrogen atoms into helium. 4. A new star is born. 1

2 nebular theory 1. gravita>onal contrac>on 2. leads to thermal fusion 3. thermal pressure pushes back against gravita>onal contrac>on 4. the star begins a life that may span billions of years. Nuclear Fusion is the combining of nuclei. Nuclear Fusion is the opposite of fission. During fusion, the sum of the parts is more than the whole. That excess mass becomes ENERGY! Fusion takes place in the core of the star thermal pressure The Solar System and Its Forma>on Nebular theory forma>on: Gravita>on between materials in the cloud pulled it inward. Spin increased in accord with the conserva>on of angular momentum. The spinning cloud conformed to the shape of a spinning disk. gravity proto planetary disk Solar Wind Credit:ESO/L. Calçada streams of ions blast outward at very high speed 2

3 Earth s magne>c field protects us from the solar wind The Solar System and Its Forma>on Nebular theory forma>on: The center of the disk is the protosun. Away from the center, planetesimals formed. Planetesimals accreted more marer to become planets. The Solar System and Its Forma>on Planets are divided into two classes: Inner planets: Mercury Venus Earth Mars Outer planets: Jupiter Saturn Uranus Neptune Meteoroids are rela>vely small (sand- grain to boulder size) pieces of debris chipped off asteroids or comets Meteor: a meteoroid that strikes Earth s atmosphere o]en called a falling star Failed Planet Forma>on Failed Planet Forma>on Comets: are masses of water, methane, and ice dirty snowballs highly ellip>cal orbital paths tail of comets swept outward from by solar wind 3

4 An image of the asteroid Lute>a from the ESA RoseRa probe Mercury The Inner Planets Earth Mars Venus ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA The 4 inner planets nearest to the are composed of high- density solid rock The Outer Planets Gas Giants: atmosphere is mainly hydrogen and helium, 1% methane, ammonia, and other molecules cough! no definite surface as occurs on the inner rocky planets have rings of ice and dust have many moons Jupiter: The Outer Planets The Outer Planets Jupiter s four largest moons The Outer Planets Jupiter s moon Europa has an ice- capped ocean, which may hold extraterrestrial life 4

5 The Brightness and Colors of Stars A star s color corresponds to it s surface temperature We measure the brightness of a star in two ways: apparent brightness the brightness as it appears to us luminosity the intrinsic brightness, independent of how bright it appears The luminosity of stars is compared to that of the, which is noted L. The Hertzsprung- Russell Diagram Graph of luminosity versus surface temperature for stars The H- R diagram is used to group and classify stars The Hertzsprung- Russell Diagram Planets Arcturus (Red Giant) Alpha Ce> (Red Giant) 5

6 Arcturus Betelgeuse A Alpha Ce> Alpha Ce> Arcturus Betelgeuse A (Red Supergiant) Cephei A (Red Hypergiant) Betelgeuse A Supernova Supernova Alpha Ce> Arcturus All these stars are within 3000 light- years of Earth, which means they are our immediate neighbors within the Milky Way Galaxy. Cephei A (Red Hypergiant) Light traveling 7,000 light years from this supernova lit up Earth's sky in the year 1006 AD white dwarf Very large stars produce black holes First discovered in 1979 by an amateur astronomer 6

7 Black Holes Black hole: what remains when a supergiant star collapses into itself named because gravita>on at its surface is so intense that even light cannot escape Black Holes Black hole Why gravita>on at the surface of a star increases when it collapses star shrinks to half its radius gravita>on at its surface increases by 4 (inverse- square law) Galaxy: huge assemblage of stars, interstellar gas, and dust most familiar Milky Way Three types of galaxies: ellip>cal irregular spiral This is a giant ellip>cal galaxy M87 A pair of irregular galaxies the Large Magellanic Cloud and neighboring Small Magellanic Cloud This is Spiral Galaxy M83, thought to be much like our Milky Way. are not the largest things in the universe. There are clusters of galaxies, and then galaxy superclusters larger than can be imagined! 7

8 Some galaxies are known as ac3ve galaxies and are emimng huge amount of energy.by comparison, these ac>ve galaxies emit many orders of magnitude more energy than our own Milky Way! Two examples of ac>ve galaxies include: Starburst galaxies form stars at a very high rate. They result from violent disturbances, such as the collision between two galaxies. Starburst galaxies with an ac3ve galac3c nucleus This image shows the a]ermath of the collision of two spiral galaxies. Areas in blue are regions of rapid star forma>on. Clusters and Superclusters The Milky Way Galaxy and its neighboring galaxies are known as the Local Group. Clusters and Superclusters Our local group is situated between the Virgo and Eridanus clusters, which all together make our Local Supercluster. Clusters and Superclusters Our Local Supercluster is part of a network of superclusters. Clusters and Superclusters As far as we can see, superclusters hold together like a foam within which there are bubbles of super large voids. 8

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