Saturday, July 24, 2010

Big Star

Fascinating press release from European Southern Observatory:

"Using a combination of instruments on ESO’s Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the Sun, or twice as much as the currently accepted limit of 150 solar masses."

Star 136a1 is the most massive star found yet. Since the time of Pierre Laplace, astronomers have believed that stars condensed from rotaing clouds of gas. How such clouds could become dense enough to start nuclear fusion has been a nagging puzzle. This immense star challenges the old theories.

If stars formed around tiny Black Holes, the inward pull of the singularity would cause the star to condense until fusion began. Presence of the singularity would allow stars to form with enormous sizes, hundreds of times our Sun's mass. The centre of star 136a1 would be a good place to find a Black Hole.

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Blogger Kea said...

Yeah, cool! (I was waiting for you to post about this). I wonder how we could detect BHs inside distant stars? I suppose it will have to wait for an improved QG chemistry and biochemistry.

11:26 AM  
Anonymous Toomas Sildvee said...

News about theory with changing velocity of light...

5:17 AM  
Anonymous Tony Smith said...

As to the PhysOrg article mentioned by Toomas Sildvee about varying c and Wun-Yi Shu
note that the Cornell arXiv put the paper 1007.1750 into the General Physics catalog.

Carlos Castro (a fellow blacklistee and friend of mine) sent me an email about that, so here it is copied below my signature.

Tony Smith


Dear Friends :

My friends in Spain told me that the Spanish newspapers have aired the story of an article ( No Big Bang) that was "partially blacklisted" by Cornell; meaning that Cornell tried to bury the article in the general physics category of the

The article by Wun-Yi Shu

it is based in the work of Mach, Dirac, Petit, Moffat, Barrow, Albretch, Magueijo and others dealing with the notion of varying speed of light and Newtonian coupling "constant".

You can model a de Sitter universe as a 3-dim sphere that was of infinite size in the past, which then contracts (de-accelerates) in time to a minimal non-zero throat size (no singularity) and then it bounces back increasing in size (accelerating) all the way to infinity.

This can be done without using a cosmological constant (dark energy) by *mimicking* the effect of the cosmological constant by means of a Brans-Dicke-Jordan scalar field,
and which is tantamount to having a varying Newtonian coupling G = G ( t ).
You can also have a varying speed of light c = c ( t ),
and varying Planck h ( t ) such that the Planck scale remains invariant.

This is what Wun-Yi Shu has done, although he does not mention the Brans-Dicke-Jordan scalar field.
To sum up, what Wun-Yi Shu did was to write the Einstein equations using a Friedmann-Robertson-Walker metric but replacing G for G ( t ) and c for c ( t ). One has to be extremely careful with doing this !!! .... the right way to do it is by introducing the Brans-Dicke-Jordan scalar field and to be very careful with the variational procedure of the action. It is very very easy to screw up.
The equations you get are not too different from those you will get by having the Brans-Dicke-Jordan scalar field coupled to gravity.
the results of Wun-Yin Shu appear to be basically a Brans-Dicke-Jordan gravity model in *disguise*, and which in turn, it is also related to the cosmological models based in actions involving a function of the curvature f ( R ), rather than the Einstein-Hilbert action linear in R.

The interesting thing is that Shu's article has appeared in the Spanish Newspapers ( ABC) despite that it has been partially blacklisted by Cornell and buried in the generla-physics category.

This also happened with Lisi's article until Lee Smolin complained, so Lisi's article was re-posted in the high energy physics theory category.

Best wishes


6:44 PM  
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11:32 PM  
Blogger DK said...

Wow Cool! Do you really think so? What would that be like? Why doesn't the star collapse inside the black hole?

2:31 AM  
Blogger Ulla said...

A fresh release in Nature. You told that in the center of Earth was a black hole :)

9:53 AM  
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12:49 AM  

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