“End? No, the journey doesn’t end here. Death is just another path, one that we all must take. The grey rain-curtain of this world rolls back, and all turns to silver glass, and then you see it.” -J.R.R. Tolkien
No matter how well we care for our bodies, they eventually wear down, give out, and we all will someday face death. Yet if there's anything to be learned from looking at the physical Universe, there's no reason to expect that death is truly the end.
Every time a star runs out of fuel and dies, no matter what type of star it is or what fate it suffers, there's always a new chance for both new stars and new life to arise from it. From stars resulting in the most massive supernovae to the smallest red dwarfs, the death of these objects is only a single step along a cosmic journey that began long before any stars existed and will continue long after the Universe ceases to resemble what we know today.
What is supposed to be the temperature of the white dwarf remnants of a red dwarf? As the mass of the red dwarf is slowly mixing and the reaction runs only in core, I suppose it would be only a few thousands degrees - so not too white. Am I right?
There is one thing about stellar collapse that I don't get. Depending on the size of the star it leaves one of three different types of corpses:
The White Dwarf, which does not have enough mass and gravity to overcome electron degeneracy pressure.
The Neutron Star, which does have enough mass and gravity to overcome the outward electron degeneracy pressure but does not have enough mass to overcome the neutron degeneracy pressure.
Finally you have the Black Hole which has enough mass and gravity to overcome all the degeneracy pressures and its collapse continues unabated.
Now here is what I don't get: If you add enough mass to an existing Neutron Star it will collapse into a Black Hole, but if you add enough mass to an existing White Dwarf it doesn't collapse into a neutron star. Instead you get a Type Ia Supernova with no remnant. Why is that? Neutron Stars are obviously not impossible to make so why is it that a White Dwarf cannot be collapsed into one by adding enough mass to overcome the electron degeneracy pressure?
Pavel, the white dwarf is the core of the star, which used to be at millions of degrees. In going nova it cooled down a lot, so hundreds of thousands of degrees is normal for soon after nova, but I don't have any figures for that.
Although it now doesn't gain more energy from fusion, it still gets energy from gravitational collapse and it doesn't have very much surface area to radiate the energy already there, so it doesn't cool very quickly from radiation alone.
but if you add enough mass to an existing White Dwarf it doesn’t collapse into a neutron star. Instead you get a Type Ia Supernova with no remnant. Why is that?
The big difference is that the Dwarf isn't so large as the core of a working star and not as dense as a neutron star, and the nova rips the core apart. Not enough *mass* is left to undergo collapse, but as far as I can recall of my Stellar Evolution, it doesn't have to leave no remnant.
Though there may have been plenty of advances and changes in the theory since I last did any science on the subject.
Sometimes death IS the end.
OK, histrionic, but trying to get this
on topic for this thread. Feel free to delete, especially if you're going to post something on the subject, Ethan.
I can undesrtand killing the project. Those who want to grind their personal axe, those who hate learning that is not what their parents knew, those just getting their kicks all make the job terrible, and it won't be paid or recognised professionally.
But I'd like to see why it can't be just hived off and given away to anyone interested in making an archive of this.
Maybe it's talking cross-purpose: some are asking for the info to archive, but the owners think it's to keep the project going, which can cause legal and ethical problems for the scientists who put their effort in. But in that case, why not make it part of the state school system, as a resource like text books, etc?
It would be a lie for me to say I know anything about their project so far or what might be the reasons of shutting it down. But pulling a plug on a repository on the internet absolutely, is baffling to me. From a purely technical standpoint, not to mention academic. While pulling the plug on the answering and support part can be somehow explained and justified... killing the whole server is not. The cost of just leaving the existing database (which can't be really big since it's plain text).. and search engine, sitting on some server is peanuts.. litrelaly.. like 100$ per year.. on a dedicated xeon with 2 TB.. it's like 1k per year... that's less than what a cleaning lady makes in a month.. no disrespect intended.
So it's just unbelivable to me from IT standpoint and 2015... noone needs to man it.. it's just software running on a pc...
In IT terms.. un-plugging a knowledge server which has 20.000 answers on it.. or just copying it to another location (their reply is likewise baffling..moving at this time is not possible.. what does that mean.. it's called "copy *.* -y ".. )... unplugging a server is same as burning down the library.. not closing it down.. since books are still there.. there's just a lock on the door.. burning it down.. since the whole server is gone..
What to me is strange is that a national laboratory would do something like that... ok.. you got financial cuts.. but like I said.. 100$ per year... and budget cuts are no reason to not copy it or give it to some other repository.. .
Already saved for future reference:
The red dwarf does not blow out its outer layers and expose naked core. So I cannot imagine what can warm the red dwarf to ten millions degree (white dwarf temperature) after burning all fuel.
Why do you address that to me?
No answer? You see *I* did not say red dwarf, so your comment about red dwarf stars really doesn't respond to anything I've said.
If you made a mistake, then an apology is the normal thing to do.