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A&C reference library

  1. Jan 26, 2004 #1

    Phobos

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    Use this topic to post links to helpful/informative websites about astronomy & cosmology.
     
    Last edited: Jan 27, 2004
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  3. Jan 26, 2004 #2

    marcus

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    A&C has a sticky! Thanks Phobos.

    Charles Bennet et al.
    http://arxiv.org/astro-ph/0302207
    see table 3 on page 33---"Best" Cosmological Parameters
    from the article
    "First Year WMAP Observations, Preliminary Maps and Basic Results"

    Charles Lineweaver
    http://arxiv.org/astro-ph/0305179
    "Inflation and the Cosmic Microwave Background"

    Michael Turner
    "Making Sense of the New Cosmology"
    http://arxiv.org/astro-ph/0202008

    Wendy Freedman and Michael Turner
    "Measuring and Understanding the Universe"
    http://arxiv.org/astro-ph/astro-ph/0308418

    The finiteness or infiniteness of space turns on how accurately they can measure a number called Omega. This is the first thing listed at the top of Bennett's Table 3.
    The current WMAP data say that Omega = 1.02 +/- 0.2 which is tantalizingly close to one. If Omega is exactly one, then space is flat and infinite. But if Omega is even slightly greater than one, then space may LOOK flat but on a very large scale it may curve around on itself and be finite. Based on observations as of right now we cannot be sure either way.
     
  4. Jan 26, 2004 #3

    marcus

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    Some links from Nereid and others

    Nereid kindly provided a link to this article about
    a wide-angle deep survey of the universe called GEMS
    http://skyandtelescope.com/news/article_1152_1.asp

    GEMS covers a patch of sky as big as the full moon
    and took thousands of images in that patch
    and made a mosaic picture of that patch which is
    real deep, going way back in time, so you see
    galaxies forming and colliding and evolving.
    The article Nereid shows a portion of the picture.
    The total GEMS picture has some 3 billion pixels.

    ------------------------

    Dark matter:
    Here's another Nereid link to a dark matter article (mapping it in a cluster by observing lensing)
    http://www.esa.int/export/esaCP/SEM...tureWeek_0.html
    ------------------------
    Neutrino astronomy:
    Has a big future potential in observational cosmology. Wolram provided these neutrino-related links:

    http://www.space.com/scienceastrono...nos_030716.html
    this gives the AMANDA2 neutrino sky map---the obseratory down near south pole.

    http://www.lns.cornell.edu/spr/2003-07/msg0052565.html
    Basic facts/estimates about the cosmic neutrino background presented
    by Ted Bunn, one of the moderators on Usenet sci.physics.research.

    ---------------------------
    High-energy Cosmic Rays:
    A great survey article about high energy cosmic ray observations
    (another window for observational cosmology to look thru)
    Floyd Stecker
    "Cosmic Physics: the High Energy Frontier"
    http://arxiv.org/astro-ph/0309027
     
    Last edited: Jan 26, 2004
  5. Jan 26, 2004 #4

    marcus

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    Online Cosmic Calculators, and more!

    two good online cosmology calculators:

    Ned Wright's
    http://www.astro.ucla.edu/~wright/CosmoCalc.html

    Siobahn Morgan's
    http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html

    homepage for Siobahn in case you want to see who she is
    http://www.earth.uni.edu/smm.html
    homepage for Ned in case you want to see who he is
    http://www.astro.ucla.edu/~wright/intro.html

    -------
    Martin Bojowald
    http://arxiv.org./abs/astro-ph/0309478
    "Quantum Gravity and the Big Bang"
    General Relativity had a glitch and
    quantizing the theory fixed the glitch so
    it no longer predicts a moment of infinite
    density and curvature (a type of singularity).
    Evolution prior to big bang is shown in some
    of the articles cited in this brief survey.
    ---------

    Labguy provided news of a recent test of General Relativity
    (which GR passed with flying colors) a binary pulsar:

    http://www.astro.ucla.edu/~wright/cosmolog.htm#04Dec03

    The technical article about the binary pulsar
    and the most stringent verification of GR to date is:

    http://arxiv.org/astro-ph/0401086

    ----------
     
  6. Jan 26, 2004 #5

    marcus

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    Useful constants and formulas

    Useful constants:

    One parsec = 3.857E16 meters

    Newton's G = 6.6742E-11 cub.meter/sq.second kg

    Best current estimate of Hubble parameter H = 71 km/s per Megaparsec

    Critical energy density derived from that = 0.85 joule per cubic km.

    In standard (SI) metric units H = 2.301E-18 per second

    H reciprocal, the "Hubble time" parameter, is 4.3E17 seconds.
    (As it happens this is roughly the same as the age of the universe.)

    The standard formula for calculating the critical density (so-called "rho crit") is

    [tex]\rho_{crit} = \frac{3c^2H^2}{8\pi G}[/tex]

    If you plug in the values for G, c, and H given here, it works out to 0.85 joule per cubic kilometer.

    This is the average energy density that is theoretically needed for space to be flat rather than positively or negatively curved. Since WMAP observations of the CMB indicate that it is flat or very nearly so, this is the density usualy assumed.
    When people say the dark energy is 73 percent they mean of this.
    Or dark matter is 23 percent, it is of this 0.85 joules per cubic km.
    Or ordinary visible matter is 4 percent, it is likewise.
     
  7. Jan 26, 2004 #6

    marcus

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    Lineweaver's article is also online in HTML at a Caltech site
    and this is sometimes handy because you can link to a particular
    page or Figure, rather than to the whole PDF file. For instance
    his "Size and destiny of the universe" Figure 14 is immediately
    accessible in two places

    Figure 14 medium scale, with caption and another figure:
    http://nedwww.ipac.caltech.edu/level5/March03/Lineweaver/Lineweaver7_7.html
    Figure 14 larger scale, without caption:
    http://nedwww.ipac.caltech.edu/level5/March03/Lineweaver/Figures/figure14.jpg
     
  8. Jan 26, 2004 #7

    marcus

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    Cragwolf's topology-of-universe links

     
  9. Jan 26, 2004 #8

    marcus

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    Nereid links about dark matter

    There's an especially good PF thread about the expansion of space. It is wideranging and touches on a bunch of cosmology and general astronomy type issues. In this thread Nereid has a good short essay on dark matter.

    https://www.physicsforums.com/showthread.php?s=&postid=135705#post135705

    In the same thread Nereid supplied some source links, which I will exerpt from one or two of her posts and include here:

    "...This page, brought to PF members by ranyart, is a good place to start:
    http://www.solstation.com/x-objects/greatatt.htm
    ...
    ...

    I don't have any good ones immediately to hand. However, this site has many excellent links:
    http://msowww.anu.edu.au/2dFGRS/

    In particular, this paper gives a flavour of how the work is done: "The 2dF Galaxy Redshift Survey: Cosmological Parameters and Galaxy Biasing", Ofer Lahev, in astro-ph/0205382

    A couple more:
    http://antwrp.gsfc.nasa.gov/apod/ap011219.html
    and if you click on the 'computer simulation' link in this page, you will get....
    ...
    ...

    A pretty picture:
    http://antwrp.gsfc.nasa.gov/apod/ap030611.html
    ...
    ..."
     
  10. Jan 26, 2004 #9

    marcus

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    Links to stuff about Jovian system

    Jimmy supplied these mosaic pictures of Europa and Jupiter

    http://members.aol.com/jrzycrim01/images/Europa.jpg
    http://members.aol.com/jrzycrim01/images/Europa2.jpg

    They are pretty remarkable.
    ----------------------------------------

    Nereid supplied a good general purpose NASA link about the moons and the Jovian system in general

    http://galileo.jpl.nasa.gov/moons/moons.html

    Also some more specialized links concerning Io's ice
    covered ocean and concerning impact basins (of which Callisto has
    a couple of examples)
    http://www.lpi.usra.edu/research/europa/thickice/
    http://www.solarviews.com/cap/index/impactbasin1.html

    ----------------------------------------

    Enigma supplied this link to tabulated data on the Jovian moons:

    http://www.the-planet-jupiter.com/moons-facts-sheet.html
    ----------------------------------------

    Here's a useful source about gravity assist maneuvers

    http://cdeagle00.tripod.com/omnum/flyby.pdf

    It gives a formula for the maximum turn angle

    [tex]2arcsin \frac{1}{1+rv_{oo}^2/\mu}[/tex]

    possible flying by a body with radius r and gravitational parameter(GM) equal to mu. Here v-infinity is the speed of approach at infinity. This can be rewritten in terms of v-infinity and v-circ, the circular orbit speed at the body's surface:

    [tex]2arcsin \frac{1}{1+v_{inf}^2/v_{circ}^2}[/tex]
    -------------------------------------------------
     
    Last edited: Jan 26, 2004
  11. Jan 26, 2004 #10

    marcus

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  12. Jan 27, 2004 #11

    marcus

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    Trodden and Carroll's course in Cosmology

    Mark Trodden and Sean Carroll just posted an 82-page
    "Introduction to Cosmology"
    http://www.arxiv.org/astro-ph/0401547

    It's a pedagogical paper summarizing a series of lectures for advanced graduate students, delivered as part of the 2002 and 2003 Theoretical Advanced Study Institutes in elementary particle physics (TASI) at the University of Colorado at Boulder.

    It seems that nowadays grad students in particle physics are often eager to move into astro/cosmo research----sometimes called "astroparticle-physics". So this course must be in demand at TASI. It certainly is not a course for beginners, in spite of the name "Introduction".

    Sean Carroll is one of half a dozen most prominent cosmologists worldwide. These notes could be useful and informative for the right reader, so I list them. They just came out today. Personally I prefer Chuck Lineweaver's and Ned Wright's more popular and intuitive style. this is more elite high-academic style.
     
  13. Jan 27, 2004 #12
    A very nice web site for amateurs like me (I especially like the FAQs):

    http://www.astronomycafe.net

    Ned Wright's calculator has been mentioned, but here are links to his brilliant tutorial and FAQ:

    http://www.astro.ucla.edu/~wright/cosmolog.htm

    http://www.astro.ucla.edu/~wright/cosmology_faq.html

    The NASA/IPAC extragalactic database contains data and literature on extragalactic objects:

    http://nedwww.ipac.caltech.edu

    There's also an excellent knowledge base, where many articles on various astronomical subjects are kept:

    http://nedwww.ipac.caltech.edu/level5/

    Some pretty cool lecture notes on galaxies:

    http://www.astr.ua.edu/keel/galaxies/

    This is one place I get my astronomy news from:

    http://www.spaceflightnow.com/news/index.html
     
  14. Jan 29, 2004 #13

    marcus

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    Beginning Astro links from a Gale17 thread

    Cragwolf thanks for posting these links at the A&C reference shelf!
    ---------------------------------
    Recently Gale17 asked about introductory Astro material and chroot (Warren) and Phobos, as well as others responded. Warren teaches an extension course in Astro for continuing ed so here are his course notes among other things:

    Warren says
    http://www.skymaps.com
    has a good monthly star map with lots of observing hints, for free.

    He also says go to star parties (nerds with telescopes hanging out for an evening in a parking lot somewhere), which are remarkably educational.

    Here are his course notes:

    http://users.vnet.net/warrenc/astro/introduction.pdf

    http://users.vnet.net/warrenc/astro/telescopes.pdf

    http://users.vnet.net/warrenc/astro/mythology.pdf

    http://users.vnet.net/warrenc/astro/stars.pdf


    Phobos says:

    Don't buy a telescope to start off. Start by learning the constellations (in the sky, not just on paper). You can get an updated sky map cheaply in the monthly magazines like Sky&Telescope or Astronomy (or even downloaded free from the internet). The first optical step should be a good pair of binoculars (not too expensive). That alone should cover you for a year or two of fun.

    After that foothold, look for a local astronomy club (I can't recommend one for NH, but this looks promising...

    http://www.nhastro.com/index.html

    Check out local planetariums & observatories (sometimes they allow the public access to their telescopes).
    --------end quotes from Warren and Phobos--------

    since the Earth is one of the planets we should have some references with facts about the Earth (even tho this is not Astronomy as usually understood) and I dont know what to suggest, but a PF poster recently cited the CIA World Factbook, maybe it will do:
    http://www.cia.gov/cia/publications/factbook/
     
    Last edited: Apr 28, 2004
  15. Jan 29, 2004 #14

    marcus

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    Our speed and direction in space

    the expansion of space (socalled "hubble flow") defines a stationary reference frame. being at rest with respect to hubble flow is the same as being at rest with respect to the Cosmic Microwave Background. CMB it gives an absolute notion of rest which cosmologists use a lot and an interesting question is, in these absolute terms, how fast and in what direction is our solar system moving?

    the COBE result reported in 1996 is that it is moving about one thousandth of the speed of light in the direction of the constellation Leo

    there is a doppler hotspot in the CMB in Leo
    and 180 degrees in the opposite direction there is a doppler coldspot
    The Microwave Background coldspot would be in Aquarius, I guess.

    COBE is authoritative, so here is the link to its 1996 report

    http://arxiv.org/PS_cache/astro-ph/pdf/9601/9601151.pdf

    "The Dipole Observed in the COBE DMR Four-Year Data"
    -----------------------------

    Now astronomers use several different systems of coordinates and
    COBE reported the Microwave Background hotspot in two different systems, ordinary celestial and galactic.

    ordinary:(11 h 12 m, -7.22 degrees)
    galactic: (264 degrees, +48 degrees)

    they actually gave more decimal places and error bounds.
    The speed they gave was equivalent to 1.231 +/- 0.008 thousandths of c, but I would just round it off to 1.23 thousandths.

    If you want to convert between ordinary coords and
    galactic coords, you can use something online at
    Johns Hopkins University. Professor Murphy's online calculator.
    Murphy's Galactic Gizmo
    http://fuse.pha.jhu.edu/support/tools/eqtogal.html

    -----------------------------
    If you go out to look at stars between 10 and 11 PM in
    the evening then you probably can see Leo any clear evening
    Feb thru May. It's where we're going. there's no destination, only
    a direction. and the speed is a thousandth of light's

    Here is a star map with the temperature of the Background as an overlay, showing the hotspot. So you can see the stars around Leo and a kindof contour map of temp:

    http://aether.lbl.gov/www/projects/u2/

    the hotspot is about 3.5 millikelvin above the average temp of the Background
     
    Last edited: Jan 29, 2004
  16. Jan 29, 2004 #15

    marcus

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    speed and direction of our local group of galaxies

    we belong to a little fleet of galaxies called the Local Group
    the main ones are Milky and Andromeda but there are a dozen or so more
    (I forget how many)
    and sometimes people wonder about the course this small fleet of galaxies is steering----what it the speed and direction is in space

    of course that is relative to the Cosmic Microwave Background, the standard frame for cosmology (also called the "Hubble flow")

    This link tells the Local Group speed and direction

    http://www.arxiv.org/abs/astro-ph/0210165

    The speed they give is 627 km per second
    This is 2.09 thousandths of the speed of light
    or roughly two thousandths (easier to remember).

    The direction is in the constellation Crater
    and since Crater is small and dim it is easier to find
    if you look for a diamond shape called Corvus
    which is practically in the same direction.
    You see Corvus to the south on spring evenings
    like april and may is a good time and it will be
    about on the meridian (the overhead northsouth line)

    Thats where Milky and our neighbors are heading, but
    Andromeda is behind us and moving faster so it is going
    to catch up eventually which will mess up both spirals some.
     
    Last edited: Jan 29, 2004
  17. Jan 29, 2004 #16

    Janus

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  18. Jan 29, 2004 #17

    marcus

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    Tsunami's link to GLAST

    Janus thanks for posting the Solar System links!

    Tsunami recently posted this GLAST link

    http://glast.gsfc.nasa.gov/

    She says that just this month (January 2004) the launch was postponed to February 2007. Another year delay. I am acting as reference librarian here and should not editorialize too much.

    However notice that Fundamental Physics has acquired a new name.
    It is no longer "high-energy particle physics" and no longer
    so tied to the great accelerators.
    The name of the Fundamental Physics game is now
    cosmology and astroparticle physics

    Lots of former HEP people are migrating.

    GLAST (gammaray large array space telescope) is for seeing gammaray bursts---explosions bigger than supernovas, maybe from two neutron stars colliding to form a black hole.

    these new space instruments are like the accelerators of the Fifties thru Seventies. they should not take second place to manned space projects which are Political Soap Opera compared with fundamental science.

    Tsunami thanx for the link
     
  19. Jan 31, 2004 #18

    marcus

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    nymph suggests an online astro course

    Gale17 asked about online stuff for getting an introduction
    to basic general astronomy and
    nymph suggested a monthly online course

    "You can find free Monthly Astronomy Lessons at.."
    http://www.synapses.co.uk/astro/
     
  20. Feb 1, 2004 #19

    marcus

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    Mars rovers, daily news on

    this site seems to have current status of the two rovers
    http://marsrovers.jpl.nasa.gov/home/index.html

    if you know of a site that's more informative about their status, or the data and pictures they're transmitting, you are most welcome to post it
     
  21. Feb 2, 2004 #20

    marcus

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    papers on inflation

    Alan Guth has a couple of recent ones (2003)

    "Time since the beginning"
    http://arxiv.org/astro-ph/0301199
    (quote: "'eternal' inflation...proposes that our universe evolved
    from an infinite tree of inflationary spacetime")

    "Inflation and cosmological perturbations"
    http://arxiv.org/astro-ph/0306275


    Stephen Hawking has a recent one (2003)

    "Cosmology from the top down"
    http://www.arxiv.org/ftp/astro-ph/papers/0305/0305562.pdf


    Alan Guth has an older, more wide-audience, talk too (2001)

    "Eternal Inflation"
    http://arxiv.org/astro-ph/0101507

    -------------

    In eternal inflation an inflating patch expands so fast that even tho the vacuum energy driving it decays exponentially (causing pockets of non-inflating space to form) there is always a larger patch still inflating. Once, by some quantum mechanical accident, this process begins, it must continue forever, and create a welter of pockets of space that have finished inflating.

    In a curious way, it appears as if the "eternal" inflation story was invented to take care of the the question of how inflation gets started-----in all spacetime it never has to start more than once (by some no-matter-how-unlikely quantum hiccup) and once started goes on forever making jillions of universes like ours. So the question of how it got started in OUR little universe is dispelled.

    If this "starting problem" had never appeared---say the standard models of physics and cosmology had, from the outset, always predicted an inflaton field causing brief exponential expansion and then decaying---then quite possibly no one would have bothered to think up this "eternal" tree of pocket universes outside our own.

    Hawking's critique of the "eternal" scenario is an example of someone who disposes of it because he thinks he doesnt need it---he thinks he has a way to describe how what we see came about (without going outside the universe we see).
    -------------------

    For a mainstream cosmologist's view (simple oneshot inflation, no fancy theory)

    Lineweaver
    "Inflation and the Cosmic Microwave Background"
    http://arxiv.org/astro-ph/0305179
    ------------------------

    Another recent paper (November 2003)

    Tsujikawa, Singh, Maartens
    "Loop quantum gravity effects on inflation and the CMB"
    "Time since the beginning"
    http://arxiv.org/astro-ph/0311015

    Loop gravity predicts a quantum bounce with a peak density and predicts this will trigger inflation, so no other story is needed about how it gets started. So topic of "eternal" never comes up.
    For other papers see references in this one. Tsujikawa and Maartens are string theorists---this is their only contribution so far to Loop gravity---so their examination of the loop gravity mechanism for inflation is especially interesting I think.
     
    Last edited: Feb 2, 2004
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