Smolin's two predictions, circa 2006, True ?

[rhody]

In "The Trouble with Physics" by Lee Smolin, Chapter 10, page 167, in a discussion about "fitness landscapes" as they apply to models of evolution, and, as a natural extension, Smolin suggests a "cosomological natural selection" in which Universe(s) are spawned from the interior of black holes.

In 1992 he published two predictions, and as of the time of the books release, 2006, he claimed were still true. (as of 2006)

One is that there should be no neutron stars more massive than 1.6 times the mass of our sun. Second, that the spectrum of fluctuations generated by inflation, observed in the cosmic microwave background, should be consistent with the simplest version of inflation, with one parameter and one inflation field.

I did a search on the maximum mass of neutron stars and there seems to no lack of papers from the mid 80's to the present and none of them predict the smaller mass that Smolin does. They are usually in the 2 - 3.5 range.

With advances in finding and cataloging stars of all types in the past five year's, does Smolin's prediction of solar masses of neutron starts still hold true ?

As to his second prediction, does it hold credibility today. If not, why not ? If so, why so ?

I threw this over the wall to the real cosmologist's who hang out here.

Thanks...

Rhody...

 

[Chronos]

Smolin's claim for neutron masses is largely upheld. I discussed exceptions with him a few years back, but, he felt the estimates were inadequately supported. I only know of one such example that remains robust at around 2 solar masses. I find it interesting the vast majority of neutron star masses have such a discrepancy with the least massive black hole[~ 5 solar masses].

 

[rhody]

In doing a little more research, this http://worldofweirdthings.com/2009/12/05/searching-for-the-biggest-stars-in-the-cosmos/" published Dec 5, 2009 states, and says that neutron stars cannot be formed unless they reach the end of their life having more than 1.5 times the mass of our sun.

This is different than ending up with a mass of less than or equal to 1.5 the mass of our sun as a neutron star. Is this in fact what Smolin was referring to ? And second, is the source of the data, I assume Nature, reliable and trustworthy to quote ?

Like the overwhelming majority of stars in the universe, our sun will die with a whisper. When stars which tip the scales at more than 1.5 times the mass of our sun end their lives, they go out with a bang, leaving either a highly compressed core we know as a neutron star, or a collapsed gravitational well we call a black hole. But when stars that exceed an astonishing 130 solar masses run out of fuel, something even stranger happens. Instead of just collapsing into a giant black hole, they completely disintegrate according to astronomers who ran the numbers on these theoretical hypergiants. Until now, there was skepticism such giant stars can even exist, much less how they explode. However, supernova SN2007bi, seen in April 2007 as implied by its name, could confirm than not only do 150+ solar mass titans exist, they behave just as the models would predict.

In 2005, the results of a star survey of our galaxy seemed to point to an upper limit on stellar mass as was implied by Eddington limit, which predicts a tipping point between a star’s gravitational forces and the force of radiation inside the star. Exceed the limit and stars begin to shed their upper layers with a fierce solar wind, losing mass. At some point, stars should no longer be able to hold themselves together and that point might well have been around 150 solar masses, an idea which was further boosted by the lack of identifiable giants exceeding this benchmark in the Milky Way. However, the Eddington limit is not absolute and is actually more of a rule of thumb than a concrete ruling on the maximum mass and luminosity of stars. Depending on what goes on inside these giant balls of superheated plasma, the limit could be violated without the predicted loss of mass. This is where SN2007bi comes into play.

Giant stars burn their fuel very quickly so an immense sun which weighs in at 130 solar masses or more, has few heavy elements in its core while it rapidly burns away. Photons created in the thermonuclear furnace of its innards keep the star from collapsing in on itself until the fuel begins running out and the sun contracts, which cranks up the heat. In these extreme conditions, photons become electrons and their antimatter counterparts, positrons. But these matter/antimatter pairs won’t provide enough outbound energy to keep the star from the now inevitable collapse. The star now contracts even further, cranking up the heat and pressure past the point of no return and a runway thermonuclear reaction in its oxygen rich core tears the titanic sun apart in a brilliant supernova event. After the blast nothing is left of its progenitor. There’s no neutron star, no black hole, just an immense cloud of freshly synthesized nickel-56 which will eventually decay into an isotope of iron. And it’s this cloud of radioactive nickel which attracted the attention of a team of astrophysicists and astronomers.

More then three sun’s worth of nickel-56 was blasted out during the SN2007bi supernova and it lit the clouds of gaseous debris for months. Plugging this into a mathematical model for how titanic supernova progenitors explode, yields an initial stellar core of 100 solar masses. That means the event itself was what’s known as a pair-instability supernova, the process we just covered above. SN2007bi’s progenitor may have weighed in at a jaw dropping 200 solar masses by an enthusiastic estimate. Just 50 solar masses more and the gamma rays generated during the blast would’ve been so intense, they’d break apart atoms streaming away from the blast, slowing down the explosion and allowing the immense core to collapse into a black hole. We can even find out how big that black hole could be and how long it would last with a pair of handy formulas.

rs = 2Gm / c2 = 2(6.673 × 10-11 m3 kg-1 s-2)(4.97 × 1032 kg) / 8.99 × 1016 m/sec = 738,150 m
tev = 3M / 3K = 3(4.97 × 1032 kg) / 3(3.89 × 1015 kg3 s-1) = 1.03 × 1082 sec or 3.26 × 1074 years

So if we ever found a supernova generated by a 250 solar mass star, the result would be a titanic black hole just shy of 1.5 million meters across and with an expected lifetime in a time range that should keep it going strong through the heat death of the known universe. Of course no one has seen any evidence of a 250 solar mass star or above, right? Well, maybe they have. On the edge of a galaxy ESO 243-49, is a 500 solar mass black hole which seems far too heavy to be formed by any known star but is absolutely puny compared to the supermassive monsters found in galactic cores. Could it be a remnant of a titanic sun? Since we now seem to have observational evidence of 130 to 250 solar mass hypergiants, maybe a rare 1,000 solar mass beast isn’t completely out of the question? Although we should note that the mechanics of such a gigantic star ever being born and stabilizing itself for at least a few million years are pretty daunting…

See: Gal-Yam, et. al, (2009). Supernova 2007bi as a pair-instability explosion Nature, 462 (7273), 624-627 DOI: 10.1038/nature08579

Rhody...

 

[twofish-quant]

It says that neutron stars cannot be formed unless they reach the end of their life having more than 1.5 times the mass of our sun.

There are two limits, the white dwarf <-> NS limit, and the neutron star <-> black hole limit. Smolin is more interested in the latter one.

And second, is the source of the data, I assume Nature, reliable and trustworthy to quote?

Depends on what it's to be quoted for. One problem is that even in good journals like Nature, when they have articles for the non-technical reader they sometimes say things that are oversimplified or misleading. For a college term paper it's fine. For a professional article, you'd probably want to quote papers that do the original calculation if for no other reason than to show that you are familiar with the literature.

 

[twofish-quant]

I did a search on the maximum mass of neutron stars and there seems to no lack of papers from the mid 80's to the present and none of them predict the smaller mass that Smolin does. They are usually in the 2 - 3.5 range.

The papers in the early 1970's were talking about 7-8 solar mass limits. Over time, the masses tend to decrease for a physical reason. Basically the limit depends on how soft nuclear material is, and how soft it is depends on the number of particle processes. The more types of particle reactions, the more ways there are for the energy within the material to get distributed and the softer things are. (One way of thinking of this is imagine hitting a brick versus hitting a beanbag).

Over time people have found more processes, and this causes the mass limit estimate to go down.

 

[twofish-quant]

Here is a more recent paper

http://diposit.ub.edu/dspace/bitstream/2445/11019/1/540740.pdf

The newer papers come up with much lower mass limits because the older papers tended to think of the neutron star as crystalized neutrons whereas the newer models think of the center as "quark soup."

 

[rhody]

Second, that the spectrum of fluctuations generated by inflation, observed in the cosmic microwave background, should be consistent with the simplest version of inflation, with one parameter and one inflation field.

TwoFish,

What you said makes perfect sense, but the ultimate test is to compare the revised theory to new measurements of neutron star masses, I assume that measurement technology has progressed and is more in line with the latest predictions.

Is there any consensus in the physic's community about Smolin's second prediction, or is it simply too "sparse" to begin with ?

Rhody...

 

[twofish-quant]

What you said makes perfect sense, but the ultimate test is to compare the revised theory to new measurements of neutron star masses, I assume that measurement technology has progressed and is more in line with the latest predictions.

Personally, I'm not too impressed by the prediction. If he made the prediction in 1975, that the black hole cut off was 1.6 solar mass, that would turn heads since it was very different from the conventional wisdom at the time. A prediction in 1992 that the cutoff would be 1.6 isn't particularly impressive since the conventional wisdom at the time that the EOS would be soft.

Also, I have to look at Smolin's logic behind that prediction since it seems to me to have a huge gap. From arXiv:hep-th/0612185 he seems to be assuming things about the supernova mechanism that aren't obviously true to me. One other thing is that if there is an observational limit to neutron stars, it's not clear at this point that it's because that is the limit is due to a black hole limitation. We don't understand very much about supernova explosions, and it's very well possible that neutron stars of 2.0 solar masses are physically possible, but that the explosion always behaves in such a way that only 1.5 solar masses are left.

 

[rhody]

Personally, I'm not too impressed by the prediction.

Thanks for the expert opinion on the subject. Without a understanding of what Smolin really meant when he made the comment, it is hard to know for sure, I scanned the page before and after it, looking for clues and could find none to add meaning to his statement to begin with. With what you said in your previous post,

The papers in the early 1970's were talking about 7-8 solar mass limits. Over time, the masses tend to decrease for a physical reason. Basically the limit depends on how soft nuclear material is, and how soft it is depends on the number of particle processes. The more types of particle reactions, the more ways there are for the energy within the material to get distributed and the softer things are. (One way of thinking of this is imagine hitting a brick versus hitting a beanbag).

Over time people have found more processes, and this causes the mass limit estimate to go down.

explains why he may have made the prediction in the first place. No big deal. Thanks for the info.

Rhody...