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  • 4 weeks later...
Cool !


Alexa, it is such a pleasure to have this organized library!

Someone called CPL Luke has just posted here at SFN about compact stars

(new kinds: quark stars, strange stars, preon stars)

so I was thinking to suggest some articles to you about that.

put them in only if you are interested and if you think they are good enough



Fridolin Weber (San Diego State University)

Strange Quark Matter and Compact Stars


58 figures, to appear in "Progress in Particle and Nuclear Physics"



F. Sandin

Compact stars in the standard model - and beyond



---here are some details about the Sandin, to be erased, or edited and used, as you think best---

16 pages, 6 figures, contribution to the 42nd course of the international school of subnuclear physics, 'How and where to go beyond the standard model', Erice, Aug. 29 - Sep. 7, 2004


In the context of the standard model of particle physics, there is a definite upper limit to the density of stable compact stars. However, if there is a deeper layer of constituents, below that of quarks and leptons, stability may be re-established far beyond this limiting density and a new class of compact stars could exist. These objects would cause gravitational lensing of white dwarfs and gamma-ray bursts, which might be observable as a diffraction pattern in the spectrum. Such observations could provide means for obtaining new clues about the fundamental particles and the origin of cold dark matter.

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  • 4 weeks later...
  • 1 month later...

the question came up in another thread about our speed and direction in space

this can be analyzed into various components. the virgo cluster is falling towards the great attractor (in direction HydraCentaurus) relative to the CMB


our local group is falling towards Virgo a little bit but also mostly towards the great attractor, and the upshot is that Milky (and the rest of Local Group) are moving towards Crater (very nearly the same Hydra Cent direction) again relative to CMB


ultimately all motions are referred to the universal rest frame defined by the hubble flow (expansion of space) and for practical purposes by the CMB.


after all the little motions, like within our galaxy etc, the sun and earth have a speed and direction relative to CMB. It is 1.23 thousandths of c in the direction of Leo.


the most authoritative source on this is the 1996 COBE report by Smoot et al





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


COBE was the first satellite to map the Cosmic Background and to measure the dipole

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.


now we have WMAP satellite, which has confirmed the dipole but it has mapped finer detail too


What about this Leo direction? Would anybody like coordinates?


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




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:




the hotspot is about 3.4 millikelvin above the average temp of the Background

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  • 3 weeks later...

I was looking thru Alexa's fine collection of links and couldnt find a history of the Galileo mission, may just have missed it, in any case here is one



that is a gripping account told by one of the people involved


Ophiolite gave a computer animation link for the Cassini mission



and he also pointed out this Wiki article on Gravity slingshot maneuvers etc.



here is a tiny bit of info about the Galileo delta-V



I want to compare Galileo and Cassini.

Wiki says that Cassini, to get to Saturn, only needed about 2 km/second

(then hooked venus twice and earth once, for free deltaV)


But IIRC Galileo, to get to Jupiter, needed a send-off of 4 km/second

(then hooked venus once and earth twice, to get the rest of what it needed)


once at jupiter it needed almost nothing, one modest burn (less than 1 km/second) snagging the planet and then it used the gravity of the jovian moons to round out the orbit.


Actually Galileo JOI burn only gave 643 m/s

they approached Jupiter at 5 km/second, but because they went in deep and used Jupiter's own gravity they only needed 0.6 km/s to capture it

however then they were in a highly elliptical orbit, so they used maybe another 0.4 km/s burn plus free gravity assist of the jovian moons to round that out and reduce the period.


here is general info about jovian moons



misc. links:

a Dutch page on rocket motors







about specific impulse of storable fuels

MMH/N204 has a vacuum Isp of ~333. N204/Hydrazine is slightly better at 340, but has tighter thermal restrictions


monomethyl hydrazine is safer to store, but straight hydrazine is better, both use nitrogen tetroxide as oxidizer


why did Galileo apparently take more of a sendof delta-V?


a quote about the rocket equation

Eric Weisstein's Mathworld


gives it


[math]\Delta v = u*ln(M_0/M)[/math]


where u is the exhaust velocity and M_0/M is the ratio

of the initial to the final mass


The exhaust velocity for MMH/N2O4 is about

3100 meters per second.


For JOI and maneuvering in the system suppose one allows

2000 m/s (twice what Galileo apparently got from its main engine)


[math]2000 = 3100*ln(M_0/M)[/math]


Estimated mass ratio of about 1.9, in the 2 km/s case,


After Jupiter-capture and all the maneuvering, probe weighs about half of what it did when it left low-earth-orbit.





for liquid hydrogen and oxygen the exhaust velocity is about 4400 meters per second


makes MMH/N2O4 look reasonably good, given that it is storable.


some grav. assist links:






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  • 2 weeks later...

Richard Batty supplied this "tour of the solar system" link




Here are his comments, including some pointers on how to make it work and a caution:


This link takes you to a page with a nice 3D virtual tour of the solar system. You do have to down load the viscape svr plug in to run it and it requires a restart but then you can see the orbtal planes and if you click on a planet you can see the orbits of moons too' date=' shame it takes the messing but I liked it. It may ask to use your own 3D graphics chip which worked ok for me. Hope this elps. P.S. if you get the downloading textures for the moons it seems to freeze but it just takes a bit to load up. P.PPP.P.S.S.SS A WARNING TO EPILEPTICS.Left click on space slows action to limits of program right click speedS it up to visual cortex in a blender type speeds.[/quote']


I think this is an "all welcome" thread unless Alexa resumes editing it. If Alexa is around then she has done a lot of work on it and it is morally her project (I think). But otherwise everyone please post whatever links you think provide useful Astro/Cosmo information: facts, pictures, calculator programs, animations, other utilities.


Thanks Richard for the latest contribution!

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  • 2 weeks later...

this thread should have Lineweavers Figure 14, "size and destiny of the universe"




here is the context in his "Inflation and the CMB"



here is the TOC for that article



here is the abstract, which has a link to a more legible PDF copy


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Here are some more Lineweaver links.

this bunch is from the Lineweaver and Davis article in March 2005 SciAm



this was a feature article "Misconceptions about BigBang"

It had some sidebars which were pictorial diagrams with a question together with right and wrong answers explained.



What kind of explosion was the big bang?



Can galaxies recede faster than light?



Can we see galaxies receding faster than light?



Why is there a cosmic redshift?



How large is the observable universe?



Do objects inside the universe expand, too?

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Thanu Padmanabhhan has come out with one of these surveys of cosmology for general audience, that a senior cosmologist may do every now and then.


Understanding Our Universe: Current Status and Open Issues

T. Padmanabhan

To appear in "100 Years of Relativity - Space-time Structure: Einstein and Beyond", A.Ashtekar (Editor), World Scientific (Singapore, 2005); 30 pages; 4 figures


"Last couple of decades have been the golden age for cosmology. High quality data confirmed the broad paradigm of standard cosmology but have thrusted upon us a preposterous composition for the universe which defies any simple explanation, thereby posing probably the greatest challenge theoretical physics has ever faced. Several aspects of these developments are critically reviewed, concentrating on conceptual issues and open questions. [Topics discussed include: Cosmological Paradigm, Growth of structures in the universe, Inflation and generation of initial perturbations, Temperature anisotropies of the CMBR, Dark energy, Cosmological Constant, Deeper issues in cosmology.]"

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Neutron Stars

Gordon Baym, Frederick K. Lamb

Comments: 3 pages,

to be published in Wiley Encyclopedia of Physics 3rd ed.

Abstract: "This short encyclopedia article, reviewing current information on neutron stars, is intended for a broad scientific audience."


short, authoritative, lots I didnt know about neutron stars

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hello Azure, I hope someone responds with some ecosystems. I dont happen to know of any links to give you.


I came in because island just contributed this Ned Wright link about dark energy or cosmological const.




Wright's whole site is great and has bunches of stuff of all kinds, but this could be especially helpful since people are always wondering about the negative pressure and its effect of speeding up expansion

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  • 3 weeks later...
Simulator Here is an awsome little download for all of you with braodband (it's kinda big 11mb) its a 3D space simulator that covers about half of the stars in the galaxy. I seriously recomend it to all you who love astronomy. Also i suggest checking out the add on section it has some pretty sweet stuff in there
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  • 4 months later...
  • 2 months later...



this is recent (October 2005)

it says it includes an animation but I can only see the stills and cannot get the animation to play, maybe you will have better luck


it is about the inspiraling and merger of two neutron stars, one of 1.2 solar masses and the other of 1.6 solar masses


as they spiral inwards they emit grav. waves

the moment they coallesce may release a GRB (gamma ray burst)

a black hole is formed


if anyone has an alternative animation they like of two neutron stars merging please post it.


thanks to Christine Dantas for this link

she has an astrophysics and quantum gravity blog



here is her blog-entry "Neutron star mergers, GRBs, and quantum gravity"


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  • 4 weeks later...




Now fielding three tutorials0

greg posted in systemic faq on November 26th, 2005


Three detailed console tutorials have recently been developed, and are now online at oklo.org.


Tutorial #1 steps through the basic features of the console, using the published radial velocity data-set for the Jupiter-like planet orbiting HD 4208.



Tutorial #2 takes a more detailed look at the console, and shows how to use periodograms and multiple-planet fitting to recover the three planetary companions (the so-called Fourpiter, Twopiter, and Dinky) orbiting Upsilon Andromedae.



Tutorial #3 tackles the tough problem of multiple-planet fitting in the presence of planet-planet interactions, and uses the console to explore the remarkable, recently published Gl 876 data set.



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links to the tutorial are in an exoplanet search "tutorial" menu in upper left corner


or try this link for tutorial #1



this for the console that you use to analyse star wobble and detect planets



this for the tutorial #2



this for the tutorial #3


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