A currently the au is 93 million miles 146 sidereal

Info icon This preview shows pages 14–16. Sign up to view the full content.

a) Currently the AU is 93 million miles 146) Sidereal Period – is the period of revolution of one body about another with respect to the stars a) How long it takes to complete one orbit (planets around the sun with respect to the stars) b) True time it takes for a planet to complete an orbit 147) Synodic Period – period of revolution about the sky with respect to the sun of a planet a) Time required for the planet to return to the same configuration again b) Time it takes from the planet to complete one orbit from the perspective of an observer 148) Measuring gravitational influences on other objects or on the stars within them, the masses of galaxies can be determined 149) Velocity of the stars depends upon the gravitational attraction from them within their galaxy and upon the mass of the star a) Consists of both the magnitude and direction of a star’s movement and denotes both the speed and direction a body is moving 150) Galaxies – majority fall into two categories a) Spirals (a.i.1) Consist of nucleus, disk, corona, and spiral arm
Image of page 14

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

(a.i.2) More than 2/3s of the most conspicuous galaxies (a.i.3) Our own galaxy (the Milky Way) and Andromeda Galaxy (M31) are spiral galaxies, Bodes Galaxy, and M33 – Traingulum Galaxy b) Ellipticals – dwarf galaxies (b.i.1) Are spherical or ellipsoidal, consist of stars with no spiral arms (b.i.2) Has many stars concentrated toward the center (b.i.3) Sparse scattering of stars extends for great distances and merges into the void (b.i.4) Do not rotate as rapidly as spirals (b.i.5) Hard to measure total size (b.i.6) Have much greater size, mass, and luminosity than do the spirals c) A small number are classified as irregular (c.i.1) About 3% of the brightest galaxies in the northern sky (c.i.2) Show no trace of circular or rotational symmetry (c.i.3) Appearance is irregular and chaotic 151) Clusters of Galaxies - now regarded as fundamental condensations of matter in the universe a) Regular Clusters (a.i.1) Have spherical symmetry and show marked central concentration (a.i.2) Very rich clusters (a.i.3) Contain thousands of members (a.i.4) Resemble those of globular star clusters (a.i.5) Consist almost entirely of elliptical galaxies b) Irregular Clusters b.i)Sometimes called open clusters b.ii) Have more formless appearance b.iii) Possess little or no spherical symmetry or central concentration b.iv) Sometimes have sub-condensations b.v) Resemble loose swarms of small clusters b.vi) Contain all kinds of galaxies, spirals, elliptical, and irregulars b.vii) More numerous than regular clusters b.viii) Can be small groups or large c) Virgo Cluster is the closest cluster of galaxies to our Milky Way Galaxy c.i) Approximately 1,300 member galaxies c.ii) Part of the larger Local Super cluster 152) Local Group a) Comprises over 35 galaxies b) Two most massive – Milky Way and Andromeda 153) Intergalactic Space – considerable matter exists that is not associated with a galaxy or cluster a) Left over gas and dust b) Rapidly moving stars escape from galaxies and from star clusters c) Collisions or tidal interactions 154)
Image of page 15
Image of page 16
This is the end of the preview. Sign up to access the rest of the document.
  • Winter '12
  • None

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern