A&C Reference Library - Astronomy & Cosmology Resources

[Phobos]

Use this topic to post links to helpful/informative websites about astronomy & cosmology.

 

[marcus]

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.

 

[marcus]

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

 

[marcus]

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

----------

 

[marcus]

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

\rho_{crit} = \frac{3c^2H^2}{8\pi G}

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.

 

[marcus]

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

 

[marcus]

Cragwolf's topology-of-universe links

Originally posted by cragwolf
Even if Omega was precisely equal to one, you could still have a finite universe: in this case, its topology would have to be multiply-connected. For example, a 3-torus, a kind of 3-dimensional version of the surface of a doughnut, is flat everywhere, but its volume is finite. General relativity (and hence the standard big bang model) has nothing to say about topology. Perhaps this is a limitation, perhaps not. Anyway, here are some articles on the subject of cosmic topology:

The Topology of the Universe by Boudewijn F. Roukema

Topology of the Universe: Theory and Observations by Jean-Pierre Luminet and Boudewijn F. Roukema

Cosmic Topology by M. Lachieze-Rey and J.P.Luminet

Topology and the Cosmic Microwave Background by Janna Levin

Constraining the Topology of the Universe by Neil J. Cornish, David N. Spergel, Glenn D. Starkman and Eiichiro Komatsu

 

[marcus]

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
...
..."

 

[marcus]

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

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

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:

2arcsin \frac{1}{1+v_{inf}^2/v_{circ}^2}
-------------------------------------------------

 

[marcus]

Picture of Callisto

http://www.solarviews.com/raw/jup/callisto.gif

it's big and has a lot of detail

 

[marcus]

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.

 

[cragwolf]

A very nice website 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

 

[marcus]

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 don't 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/

 

[marcus]

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

 

[marcus]

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.

 

[Janus]

A nice coleection of info on the Solar System.

http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.html

Including these appendixes:
http://seds.lpl.arizona.edu/nineplanets/nineplanets/data.html

http://seds.lpl.arizona.edu/nineplanets/nineplanets/data1.html

http://seds.lpl.arizona.edu/nineplanets/nineplanets/data2.html

 

[marcus]

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 thanks for the link

 

[marcus]

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/

 

[marcus]

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

 

[marcus]

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 doesn't 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.

 

[marcus]

Wolram supplied a link (in Astrophysics forum) about
an interesting object. It is a spinning black hole that
periodically produces jets along its axis of rotation

http://heasarc.gsfc.nasa.gov/docs/xte/learning_center/discover_0198.html

there are some schematic pictures describing what is going on
and some lightcurves, and an audio soundfile that I haven't listened to.

 

[marcus]

High energy neutrino astronomy

http://www.arxiv.org/abs/astro-ph/0402083

this recent article might be a useful source for someone interested
in neutrino astronomy----AMANDA, icecube, the future and an
overall perspective about it.

"High energy neutrino astronomy"
can't think of the author's name just now

Floyd Stecker's article also covers neutrino observation, there's a link to it earlier in the thread

 

[Nereid]

AAVSO free document on CCDs, observing etc

If you are an amateur astronomer (or thinking about it), and are wondering about CCDs, what they can do, how you can use them, etc, I recommend you spend 30 minutes or so reading through the AAVSO* "CCD Observing Manual":
http://www.aavso.org/observing/programs/ccd/manual/index.shtml#new

This has got to be the best ~30 min intro to the subject on the web.

It covers telescopes, CCDs, computers, software, and (most important for real individuals) the actual time and $$$ that is involved in actually *doing* this stuff!

*despite its name - American Association of Variable Star Observers - it's a truly international non-professional organisation, with an incredibly strong contribution from 'down under' - yah Aussies!

 

[marcus]

thanks Nereid! looking forward to more of your links
on this "reference shelf" thread.

 

[marcus]

This article by Lev Okun has been cited several times IIRC,
most recently by pmb_pby:

http://xxx.lanl.gov/abs/physics/9907017

this is the article about the gravitational redshift.
Lev Okun's 1989 article about the concept of mass
is only available in hard copy AFAIK. If someone knows
where it has been put online please let us know.

 

[marcus]

Tamara Davis thesis "Fundamental Aspects..."

http://arxiv.org/astro-ph/0402278

Tamara Davis thesis (advisor Charles Lineweaver)
"Fundamental Aspects of the Expansion of the Universe and Cosmic Horizons"

------------------------
http://arxiv.org./abs/astro-ph/0310808

Davis and Lineweaver
"Expanding Confusion:common misconceptions of cosmological horizons and the superluminal expansion of the Universe"

Lineweaver and Davis are at the University of New South Wales.
Lineweaver was one of the leaders of the COBE project (satellite
mapping the cosmic microwave background in the 1990s)
----------------------------
http://arxiv.org./abs/astro-ph/0401024
Lineweaver et al
"The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way"

9 pages, 4 figs. Published in Science, 2 January 2004


We modeled the evolution of the Milky Way to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun.

 

[marcus]

Barry Madore's cosmology knowledgebase

http://nedwww.ipac.caltech.edu/level5/cos_par.html
http://nedwww.ipac.caltech.edu/level5/toc.html
http://nedwww.ipac.caltech.edu/leve...ary/frames.html

"Level 5 knowledgebase for extragalactic astronomy and cosmology"
it has essays on various topics by famous people
and a glossary
it is put together by a CalTech guy
the site has one many awards
and is supported by prestigious funding agencies
arivero reminded me about this site

 

[marcus]

Powers of 10 Java visual from Talahassee

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html

this java applet goes from a view of the milkyway galaxy down
to subatomic particles in steps of ten
you can control it and back it up if you want
or just let it go

I can't say how this compares to other things like it that
will play on your computer. A friend recommended it.
anyone have other visuals they especially want to recommend?

 

[marcus]

Probing Dark Energy and Acceleration (Eric Linder)

There is a new paper posted by Eric Linder
"Probing Gravitation, Dark Energy, and Acceleration"

http://arxiv.org./astro-ph/0402503

it explores the different explanations of accelerating expansion

cosmological constant (w = -1)
quintessence
some braneworld picture (which he says tends to imply
that w > - 0.7 under realistic assumptions about the density of matter)

he seems fairly sanguine about upcoming possibilities for comparing and distinguishing between models, as the history of the universe's scale-factor becomes a(t) better-known

reputable discussion of the various explanations for acceleration

 

[marcus]

new work on black holes

It was Ranyart who mentioned this one

http://arxiv.org/hep-th/0311030

"Black Holes in de Sitter Space: Masses, Energies and Entropy Bounds"

a paper by Corichi and Gomberoff analysing a black hole (entropy, hawking radiation, evaporation and all that) in the "isolated horizon" situation.

In that situation there are two horizons---the BH's own event horizon and a cosmological horizon (from beyond which nothing can ever come)
Ashtekar has been doing a lot of research on this situation. It is realistic in the sense that assuming a positive cosmological constant we really do have a cosm. horizon. Accelerating expansion causes it.

Having the other horizon helps limit things and makes it possible to do analysis where one could not before (with the BH just sitting by itself in an infinite expanse of space).

A couple of other BH articles came to light recently
-------------------

Maulik Parikh
http://arxiv.org/hep-th/0402166
"Energy Conservation and Hawking Radiation"
---------------------

Maulik Parikh and Frank Wilczek
http://arxiv.org/hep-th/9907001
"Hawking Radiation as Tunneling"