Star Formation

[Nereid]

Hello Neried

So far your comments prove to me that you read words out of context and place meanings that you want.

Thats OK.

Hmm, if you say so.

I was, however, rather hoping you'd share your methods (the HOW) with us ... the ones you have used, and use today, to decide, to test, to assess, (etc) the various ideas that you read.

The danger in that is that you will lead and give information along that path. I just hope you are right.

I have previously asked for proof of the BBT.

And I, along with many others, have previously told you that you are in the wrong forum if you're looking for proof, of anything, scientifically.

If it's maths you want (where 'proof' is possible), then may I suggest you find a math-oriented forum?

If it's religion you want (where, as I understand it, many claims to 'proof' are made), then may I suggest you find a religious forum?

and you keep on giving me links without evidence and outdated information regardless if it is written by some scientist.

You show me how you test or asses papers.

[snip]

Hmm ... I think the disconnect is in what scientists (astronomers, astrophysicists, cosmologists) regard as 'evidence' and what you consider such to be.

Perhaps we can best help by trying to understand better what the methods you use to assess (etc) models and theories in the cosmological domain are.

Or perhaps we could, together, go through some recent, landmark papers, such as the Spergel et al. one on cosmological implications of the Year 3 WMAP results? Doing this would enable us to see, via concrete detail, just where the disconnect lies (between your methods and those of contemporary astronomers).

[GOD]

I think most stellar remnants max out around 0^18kg/m^3 or so. Beyond that you end up with a black hole, I would think.

Qev: Here are a couple thoughts for you to ponder: At what mass/energy do you think black holes max out at? Beyond that, what do you think you end up with?

[harry]

Hello All

Hello God

Many cosmologists think that Neutron stars are made of a Neutrons forming a neucleon and that Neutron reulsion stops further collapse of the neucleon. Density about 10^17 Kg /m3 Our sun would fit in a 10Km ball. The size of the neucleon will determine the EMR/G waves that may prevent EMR from escaping and thus create a so called black hole.


Black holes:

Other cosmologist think that a further collapse is possible a quark composite. Density about 10^18 to 10^24 Kg/m3. Our sun would fit in a soccer ball.

Further compaction in reference to theoretical preon-particles may produce density from 10^25 to 10^35. Our sun would fit in an unthinkable size. A so called singularity. Pin size.

[harry]

Hello Neried

Please do not think that I have not taken your advice.

Reading up on your post

You Said

Sabine Hossenfelder and Stefan Scherer have a wonderful physics blog called BackRe (Action) - "Events on the world lines of two theoretical physicists, from the horizon to timelike infinity. A scientifically minded blog with varying amounts of entertainment, distractions, and every day trivialities."

Several of their 2007 "A Pottl a Day" blogs are worth mention in connection with 'degenerate matter' and the early universe.

The Phase Diagram of Nuclear Matter, which talks about states of matter that are far, far beyond the ones we encounter in everyday life, but some of which are relevant to the early universe. Note: no mention of 'degenerate' or 'degeneracy'.

Running Coupling Constants, which is also highly relevant to the (even earlier) universe; again, no mention of the 'd' word.

Asymptotic Freedom and the Coupling Constant of QCD nicely bridges the above two, with a closer look at just one coupling constant.

Finally, The Hadron-Muon Branching Ratio shows nicely how complicated something as seemingly simple as electron-positron annihilation actually is.

These are some of the many inputs used to model the very early universe, when it was very hot and very dense ... before protons (etc) had independent identities, for example.

Very interesting reading, thank you for the info and your patients.

[harry]

G'day from the land of ozzzzz

I came across this link

ESO Press Release 05/05
3 March 2005
For immediate release
Undercover Stars Among Exoplanet Candidates
Very Large Telescope Finds Planet-Sized Transiting Star

http://www.eso.org/public/outreach/pres ... 05-05.html

This companion is 96 times heavier than planet Jupiter but only 16% larger. It is the first time that direct observations demonstrate that stars less massive than 1/10th of the solar mass are of nearly the same size as giant planets. This fact will obviously have to be taken into account during the current search for transiting exoplanets.
In addition, the observations with the Very Large Telescope have led to the discovery of seven new eclipsing binaries, that harbour stars with masses below one-third the mass of the Sun, a real bonanza for the astronomers.

[harry]

G'day from the land of ozzzzzzz


When I come across info, I love to share.

Old Star's "Rebirth" Gives Astronomers Surprises
http://www.nrao.edu/pr/2005/sakurai/

Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope are taking advantage of a once-in-a-lifetime opportunity to watch an old star suddenly stir back into new activity after coming to the end of its normal life. Their surprising results have forced them to change their ideas of how such an old, white dwarf star can re-ignite its nuclear furnace for one final blast of energy.
Radio/Optical Images of Sakurai's Object:
Color image shows nebula ejected thousands
of years ago. Contours indicate radio emission.
Inset is Hubble Space Telescope image, with
contours indicating radio emission; this
inset shows just the central part of the
region.

CREDIT: Hajduk et al., NRAO/AUI/NSF,
ESO, StSci, NASA

Computer simulations had predicted a series of events that would follow such a re-ignition of fusion reactions, but the star didn't follow the script -- events moved 100 times more quickly than the simulations predicted.

"We've now produced a new theoretical model of how this process works, and the VLA observations have provided the first evidence supporting our new model," said Albert Zijlstra, of the University of Manchester in the United Kingdom. Zijlstra and his colleagues presented their findings in the April 8 issue of the journal Science.

The astronomers studied a star known as V4334 Sgr, in the constellation Sagittarius. It is better known as "Sakurai's Object," after Japanese amateur astronomer Yukio Sakurai, who discovered it on February 20, 1996, when it suddenly burst into new brightness. At first, astronomers thought the outburst was a common nova explosion, but further study showed that Sakurai's Object was anything but common.

The star is an old white dwarf that had run out of hydrogen fuel for nuclear fusion reactions in its core. Astronomers believe that some such stars can undergo a final burst of fusion in a shell of helium that surrounds a core of heavier nuclei such as carbon and oxygen. However, the outburst of Sakurai's Object is the first such blast seen in modern times. Stellar outbursts observed in 1670 and 1918 may have been caused by the same phenomenon.

[Doum]

" The revised models predicted that the star should rapidly reheat and begin to ionize gases in its surrounding region. "This is what we now see in our latest VLA observations," Zijlstra said."

Theory OK now.


And,


"The scientists continue to observe Sakurai's Object to take advantage of the rare opportunity to learn about the process of re-ignition. They are making new VLA observations just this month. Their new models predict that the star will heat very quickly, then slowly cool again, cooling back to its current temperature about the year 2200. They think there will be one more reheating episode before it starts its final cooling to a stellar cinder."

So that star is taking his final breath. We now know more precisely how it end his day as a star. No rebirth here. Except the title.

[harry]

Hello Doum

I agree no rebirth,,,,,,,,,,,,,maybe rejuvination,,,,a phase in the days of a star.

One main property for the formation of stars is a gravity sink.

[harry]

G'day from the land of ozzzzzzzz


This may be an interesting link :

http://lanl.arxiv.org/abs/astro-ph/0605268
Remarks on Rapid vs. Slow Star Formation

Authors: Javier Ballesteros-Paredes (CRyA-UNAM), Lee Hartmann (University of Michigan)
(Submitted on 10 May 2006 (v1), last revised 23 Oct 2006 (this version, v2))

Abstract: We discuss problems with some observational estimates indicating long protostellar core lifetimes and large stellar age spreads in molecular clouds. We also point out some additional observational constraints which suggest that protostellar cores do not have long lifetimes before collapsing. For external galaxies, we argue that the widths of spiral arms does not imply a long star-formation process, since the formation of massive stars will disrupt molecular clouds, move material around, compress it in other regions which produce new star-forming clouds. Thus, it seems unavoidable that this cyclical process will result in an extended period of enhanced star formation, which does not represent the survival time of any individual molecular cloud. We argue that the rapid star formation indicated observationally is also easier to understand theoretically than the traditional scenario of slow quasi-static contraction with ambipolar diffusion.

I know now that the more I read the more I find that I'm just starting to learn about the universe.

[harry]

Hello Wenewen

What do you mean?

[Doum]

Hello All

Interesting link on jets and starformation

http://www.nasa.gov/mission_pages/chand ... 7-139.html



Very interesting.

Main stream cosmology assumes that the jet is created by infalling matter.

In my opinion and not that of main stream is mostly matter from the core of the black hole and the jet powered by the plasma properties of the core. What else would produce such a drive and give the jet an electromagnetic properties protecting it from the black hole huge gravity.

Since most do not know one from the other, than one option is as good as the other.

Here are some news on infalling matter nd how it seem to work:

http://www.space.com/scienceastronomy/b ... 21111.html

It is also said in there:
In June, scientists reported that the jets from stellar black holes are indeed related to the accretion disks. And earlier this month, a research team revealed a remarkable set of observations detailing the entire life cycle of a jet emanating from a stellar black hole.

Here another link:

http://www.space.com/scienceastronomy/a ... 20606.html


Enjoy!

[harry]

G'day Doum


Your link

Harnessing Hyperactivity: Lab Device Mimics Black Hole Jets
http://www.space.com/scienceastronomy/b ... 21111.html

But the forces and processes that funnel and propel these magnificent structures, which can span light-years of space, are mostly mysterious.

If you have time, read up on Z-pinch experiments. Very interesting in the formation of jets and the formation of Neutrons and!!!!!!!!!! their compaction.

and the link

Study Reveals Origin of Jets from Supermassive Black Hole
http://www.space.com/scienceastronomy/a ... 20606.html

The link did not reveal the origin or the Mechanism.


If you want scientific info on this subject let me know.

[Martin]

Harry,

Entropy must increase. I am not saying you are incorrect nor am I saying the BB model is entirely correct. However, the Laws of Thermal Dynamics must be addressed by any theory.

[harry]

G'day martin

Yep


What else?

[harry]

G'day Martin

This maybe of interest to you

http://arxiv.org/abs/astro-ph/0610835

Entropy Growth and the Dark Energy Equation of State

Authors: Wilfried Buchmuller, Joerg Jaeckel
(Submitted on 27 Oct 2006)

Abstract: We revisit the conjecture of a generalized second law of thermodynamics which states that the combined entropy of matter and horizons must grow. In an expanding universe a generalized second law restricts the equation of state. In particular, it conflicts with long phases of a phantom, w<-1, equation of state.

and another on Hybris stars

http://arxiv.org/abs/astro-ph/0609641

Thermal evolution of rotating hybrid stars

Authors: kang Miao, Zheng Xiaoping
(Submitted on 23 Sep 2006 (v1), last revised 28 Feb 2007 (this version, v2))

Abstract: As a neutron star spins down, the nuclear matter continuously is converted into quark matter due to the core density increase and then latent heat is released. We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. We have taken into account the conversion in the frame of the general theory of relativity. The released energy has been estimated as a function of change rate of deconfinement baryon number. Numerical solutions to cooling equation are obtained to be very different from the without heating effect. The results show that neutron stars may be heated to higher temperature which is well-matched with pulsar's data despite onset of fast cooling in neutron stars with quark matter core. It is also found that heating effect has magnetic field strength dependence. This feature could be particularly interesting for high temperature of low-field millisecond pulsar at late stage. The high temperature could fit the observed temperature for PSR J0437-4715.

Do I understand whats happening?

No way, not yet, maybe never,,,,,,,,,,,,,,,,,just learning.


The formation of stars is so complex, that I feel that I'm just learning.

[harry]

G'day

This email I just got.

News Release - heic0817: Hubble sees magnetic monster in erupting galaxy
http://www.spacetelescope.org/news/html/heic0817.html

20-Aug-2008: The Hubble Space Telescope has found the answer to a long-standing puzzle by resolving giant but delicate filaments shaped by a strong magnetic field around the active galaxy NGC 1275. It is the most striking example of the influence of these immense tentacles of extragalactic magnetic fields, say researchers.

This will help in explaining star formations.

These filaments are the only visible-light manifestation of the intricate relationship between the central black hole and the surrounding cluster gas. They provide important clues about how giant black holes affect their surrounding environment.

[harry]

G'day from the land of ozzzzz

This maybe an interest, in the formation of stars.

http://arxiv.org/abs/0806.4570

AGN Jet-induced Feedback in Galaxies. I. Suppression of Star Formation

Authors: V. Antonuccio-Delogu (Oxford and Catania), J. Silk (Oxford)
(Submitted on 27 Jun 2008 (v1), last revised 1 Jul 2008 (this version, v2))

Abstract: (Abridged) We study the interaction of relativistic jets from AGNs with the ISM in their host galaxy, using a series of Adaptive Mesh Refinement simulations of the evolution of the interaction between the cocoon produced by the jet with a dense cloud, placed very near the cocoon's path. We vary only the jet's input power between P_{jet} = 10^{41}-10^{47} {\rm erg/sec}. The density Probability Distribution Function (PDF) within the cocoon can be described in terms of two distinct components, which are also spatially distinct: a low- and a high-density component. The PDF of the post-shocked region is well approximated by a modified lognormal distribution, for all values of $P_{jet}$. During the active phase, when the jet is fed by the AGN, the cloud is subject both to compression and stripping, which tend to increase its density and diminish its total mass. When the jet is switched off (i.e. during the passive phase) the shocked cloud cools further and tends to become more filamentary, under the action of a back-flow which develops within the cocoon. We study the evolution of the star formation rate within the cloud, assuming that is determined by a Schmidt-Kennicutt law, and we analyze the different physical factors which have an impact on the star formation rate. We show that, although the star formation rate can occasionally increase, on time scales of the order of $10^{5}-10^{6}$ yrs, star formation will be inhibited and the cloud fragments. The cooling time of the environment within which the cloud is embedded is however very long: thus, star formation from the fragmented cloud remains strongly inhibited.

http://arxiv.org/abs/0807.0740

The role of jets in the formation of planets, stars, and galaxies

Authors: Ralph E. Pudritz, Robi Banerjee, Rachid Ouyed
(Submitted on 4 Jul 2008 (v1), last revised 21 Aug 2008 (this version, v2))

Abstract: Astrophysical jets are associated with the formation of young stars of all masses, stellar and massive black holes, and perhaps even with the formation of massive planets. Their role in the formation of planets, stars, and galaxies is increasingly appreciated and probably reflects a deep connection between the accretion flows - by which stars and black holes may be formed - and the efficiency by which magnetic torques can remove angular momentum from such flows. We compare the properties and physics of jets in both non-relativistic and relativistic systems and trace, by means of theoretical argument and numerical simulations, the physical connections between these different phenomena. We discuss the properties of jets from young stars and black holes, give some basic theoretical results that underpin the origin of jets in these systems, and then show results of recent simulations on jet production in collapsing star-forming cores as well as from jets around rotating Kerr black holes.

[harry]

G'day from the land of ozzzzzzzzz

This link is quite interesting in reference to recycling or feedback.
Monthly Notices of the Royal Astronomical Society, Volume 387, Issue 2, pp. 577-600. (MNRAS Homepage)
Jun-08


http://cdsads.u-strasbg.fr/abs/2008MNRAS.387..577O
Mass, metal, and energy feedback in cosmological simulations

Abstract

Using GADGET-2 cosmological hydrodynamic simulations including an observationally constrained model for galactic outflows, we investigate how feedback from star formation distributes mass, metals, and energy on cosmic scales from z = 6 -> 0. We include instantaneous enrichment from Type II supernovae (SNe), as well as delayed enrichment from Type Ia SNe and stellar [asymptotic giant branch (AGB)] mass loss, and we individually track carbon, oxygen, silicon and iron using the latest yields. Following on the success of the momentum-driven wind scalings, we improve our implementation by using an on-the-fly galaxy finder to derive wind properties based on host galaxy masses. By tracking wind particles in a suite of simulations, we find: (1) wind material re-accretes on to a galaxy (usually the same one it left) on a recycling time-scale that varies inversely with galaxy mass (e.g. <1 Gyr for L* galaxies at z = 0). Hence, metals driven into the intergalactic medium by galactic superwinds cannot be assumed to leave their galaxy forever. Wind material is typically recycled several times; the median number of ejections for a given wind particle is 3, so by z = 0 the total mass ejected in winds exceeds 0.5Ωb. (2) The physical distance winds travel is fairly independent of redshift and galaxy mass (~60-100 physical kpc, with a mild increase to lower masses and redshifts). For sizeable galaxies at later epochs, winds typically do not escape the galaxy halo, and rain back down in a halo fountain. High-z galaxies enrich a significantly larger comoving volume of the intergalactic medium (IGM), with metals migrating back into galaxies to lower z. (3) The stellar mass of the typical galaxy responsible for every form of feedback (mass, metal, and energy) grows by ~30 times between z = 6 -> 2, but only approximately two to three times between z = 2 -> 0, and is around or below L* at all epochs. (4) The energy imparted into winds scales with M1/3gal, and is roughly half the SN energy. Given radiative losses, energy from another source (such as photons from young stars) may be required to distribute cosmic metals as observed. (5) The production of all four metals tracked is globally dominated by Type II SNe at all epochs. However, intracluster gas iron content triples as a result of non-Type II sources, and the low-z IGM carbon content is boosted significantly by AGB feedback. This is mostly because gas is returned into the interstellar medium to form one-third more stars by z = 0, appreciably enhancing cosmic star formation at z <~ 1.

[harry]

G'day from the land of ozzzzzzzz


Big galaxy collisions can stunt star formation
http://www.astronomy.com/asy/default.aspx?c=a&id=7471

"Our data show that this system represents the nearest recent collision between a large elliptical galaxy and a large spiral," said Jeffrey Kenney of Yale University, lead author of a paper to be published in a November 2008 issue of Astrophysical Journal Letters. "This discovery provides some of the clearest evidence yet for high-speed collisions between large galaxies, and it suggests that the sequences of such collisions are a plausible alternative to black holes in trying to explain the mystery of what process turns off star formation in the biggest galaxies."

I disagree with the quote.

It basis its evidence on

Spectroscopy of selected regions along the filament between M86 and NGC 4438, obtained with the Sparsepak Integral Field Unit instrument on the WIYN 3.5-meter telescope on Kitt Peak, shows a fairly smooth velocity gradient between the galaxies, supporting the collision scenario. There are no obvious stars in the filaments.

What do you think?

[harry]

G'day from the land of ozzzzzzzzzzzzzz

This is quite interesting reading.

Monolithic or hierarchical star formation? A new statistical analysis
Authors: Marios Kampakoglou, Roberto Trotta, Joe Silk (Oxford Astrophysics)
(Submitted on 7 Sep 2007 (v1), last revised 23 Nov 2007 (this version, v2))

Abstract: We consider an analytic model of cosmic star formation which incorporates supernova feedback, gas accretion and enriched outflows, reproducing the history of cosmic star formation, metallicity, supernovae type II rates and the fraction of baryons allocated to structures. We present a new statistical treatment of the available observational data on the star formation rate and metallicity that accounts for the presence of possible systematics. We then employ a Bayesian Markov Chain Monte Carlo method to compare the predictions of our model with observations and derive constraints on the 7 free parameters of the model. We find that the dust correction scheme one chooses to adopt for the star formation data is critical in determining which scenario is favoured between a hierarchical star formation model, where star formation is prolonged by accretion, infall and merging, and a monolithic scenario, where star formation is rapid and efficient. We distinguish between these modes by defining a characteristic minimum mass, M > 10^{11} M_solar, in our fiducial model, for early type galaxies where star formation occurs efficiently. Our results indicate that the hierarchical star formation model can achieve better agreement with the data, but that this requires a high efficiency of supernova-driven outflows. In a monolithic model, our analysis points to the need for a mechanism that drives metal-poor winds, perhaps in the form of supermassive black hole-induced outflows. Furthermore, the relative absence of star formation beyond z ~ 5 in the monolithic scenario requires an alternative mechanism to dwarf galaxies for reionizing the universe at z ~ 11, as required by observations of the microwave background. While the monolithic scenario is less favoured in terms of its quality-of-fit, it cannot yet be excluded.

[harry]

G'day from the land of ozzzzzzz

THis link shows the power in reforming a galaxy and its influence of star formation.

http://chandra.harvard.edu/photo/2008/m84/
M84:
Huge Russian Dolls Surrounding a Galaxy