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#21
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 16/05/2011 3:53 PM, Brad Guth wrote:
They'll also have to encounter a substantial molecular cloud of hydrogen and helium. Is there one of those nearby? Why would need to find a cloud? They're likely already made of helium. Yousuf Khan |
#22
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Some colliding white dwarfs can reignite fusion rather than go supernova
"Yousuf Khan" wrote in message ... | On 16/05/2011 3:53 PM, Brad Guth wrote: | They'll also have to encounter a substantial molecular cloud of | hydrogen and helium. Is there one of those nearby? | | Why would need to find a cloud? They're likely already made of helium. | | Yousuf Khan They are for more likely to be made of bull****. Why would (you) need to make up idiotic crap? |
#23
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 16/05/2011 6:55 PM, Sam Wormley wrote:
Carbon/Oxygen core makes up at least 99% of the White Dwarf's mass. Not if they're small white dwarfs. Some white dwarfs stop at the helium stage. Take a couple of those small white dwarf husks and bang em together, and you can restart helium fusion. The examples they gave here are a 0.4 solar mass white dwarf and a 0.1 solar mass white dwarf merger. In the end, it'll probably end life as another carbon-oxygen white dwarf. Yousuf Khan |
#24
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 16/05/2011 7:29 PM, palsing wrote:
I find it curious that the article you referenced states that "in this case, the white dwarfs will actually reignite nuclear fusion, creating a brand new star just like our Sun", since our sun still has most of the hydrogen it started with and these guys have none... but perhaps I'm missing something here. The article listed white dwarfs in the range of 0.43 for primary and 0.17 for secondary. The primary would be a carbon-oxygen WD and the secondary would be a helium WD. The helium being deposited on the surface as the secondary is ripped apart can then restart helium fusion due to the combined gravity of the merged WD. Yousuf Khan |
#25
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The end of star-making days
On 16/05/2011 8:16 PM, herbert glazier wrote:
Sam my G=EMC^2 predicts the days of star making has to end.(no more interstellar gas for gravity to compress. Gravity still will do what it does best and that is to evolve the stuff it created. The end is when all it created is left in black holes,neutron stars,and white dwarfs. Sam They are not really the end,but that is the spacetime with no universe life,or any physical matter. Cheer up Sam it will always have "time,space energy,and gravity" Its my last picture,so Sam Get the picture TreBert It's going to take a while to reach that point. There's more mass within the intergalactic gas between galaxies, than there is in the galaxies themselves. If a galaxy runs out of gas, its central blackhole will stop blowing gas away, and instead that gas will fall back into the galaxy, restarting star formation. Or even more wildly, the intergalactic gas will start forming new baby galaxies between the old galaxies. I figure this stage will last a trillion years (or two orders of magnitude older than the universe is now), with continuous cycles of gas falling into old galaxies and/or new baby galaxies forming. Yousuf Khan |
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 16/05/2011 7:21 PM, Eric Gisse wrote:
On May 15, 10:36 pm, Yousuf wrote: Colliding white dwarfs give each other a new lease on life "Astronomers recently discovered the rather memorably named SDSS J010657.39–100003.3, which is a binary star system composed of two white dwarfs, one of which is 17% the Sun's mass, while the other is about 43%. The two orbit each other at a distance of just 140,000 miles, which is even closer than the distance between the Earth and the Moon. The two rotate each other at about a million miles per hour. A factor of 4 or so closer in separation compared to the Hulse-Taylor pulsar system, but with significantly less mass. And no pulsar for timing. This system will decay via gravitational radiation too. Wonder how long it'd take. 37 million years, according to the article. When white dwarfs collide, one of two things can happen: if the combined masses is greater than 140% of the Sun, the collision creates a supernova. But in this case, the white dwarfs will actually reignite nuclear fusion, creating a brand new star just like our Sun that will, after another few billion years of renewed life, cool down into yet another white dwarf."http://ca.io9.com/5801997/colliding-white-dwarfs-give-each-other-a-ne... I wonder what type of supernova that would be. Not a 1a - that's a helium flash from accretion, and not a II which is a core collapse...probably be rather noisy, perhaps a candidate the fast variety of GRB's? Depending on the mass and mass ratios between the two white dwarfs, the choices a (1) sub-luminous SNe Ia, (2) super-luminous SNe Ia, or (3) no supernova at all, just a re-awakening of stellar nucleosynthesis. Obviously the subject of previously mentioned article is about the #3 possibility, where the two WD's won't approach the Chandrasekhar limit even after merger. However, for much larger WD's where their combined mass exceeds the Chandrasekhar Limit, the following study suggests that the difference in mass between the primary and secondary WD's makes a difference to what kind of SNe Ia explosion will occur. They suggest that since there is more mass being ejected, but the kinetic energy is the same, the ejecta is travelling at lower speeds, thus producing the sub-luminous SNe Ia effect. [1102.1354] Violent mergers of nearly equal-mass white dwarf as progenitors of subluminous Type Ia supernovae http://arxiv.org/abs/1102.1354 Yousuf Khan |
#27
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 5/17/11 12:33 AM, palsing wrote:
On May 16, 9:53 pm, Sam wrote: If this paper is accurate http://adsabs.harvard.edu/abs/2011MNRAS.tmpL.233K Completely off-topic for this thread, but in that paper it says that some of the data was obtained using the 2.1 meter telescope at McDonald in Texas. I have had the pleasure of using that same telescope optically from dusk to dawn on 3 occasions, once in 2000 and a full weekend in 2006. 82" of glass, 812X at the lowest power and sub- arc-second seeing on one night makes for very memorable and remarkable experiences. If you like such observing reports, mine is here... http://www.pnalsing.com/82-report \Paul A Thanks Paul! -Sam |
#28
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 5/17/11 1:02 AM, Yousuf Khan wrote:
On 16/05/2011 10:05 AM, Sam Wormley wrote: Since white dwarf contain little or no hydrogen the later ain't gonna happen. Two white dwarfs would likely create a Type I supernova or form a neutron star. Depending on the size of the white dwarf remnants, they would contain a lot of helium at the very least, and they can restart helium fusion rather than hydrogen fusion. Besides, when a white dwarf goes Type Ia supernova, what do you think makes it go kablooey? It was a runaway fusion process. Yousuf Khan And because the components are degenerate matter, the fusion will be runaway! |
#29
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 5/17/11 1:16 AM, Yousuf Khan wrote:
On 16/05/2011 7:29 PM, palsing wrote: I find it curious that the article you referenced states that "in this case, the white dwarfs will actually reignite nuclear fusion, creating a brand new star just like our Sun", since our sun still has most of the hydrogen it started with and these guys have none... but perhaps I'm missing something here. The article listed white dwarfs in the range of 0.43 for primary and 0.17 for secondary. The primary would be a carbon-oxygen WD and the secondary would be a helium WD. The helium being deposited on the surface as the secondary is ripped apart can then restart helium fusion due to the combined gravity of the merged WD. Yousuf Khan We are dealing with degenerate matter here--the fusion will be a run-a-way blowing the thing to smithereens. |
#30
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Some colliding white dwarfs can reignite fusion rather than gosupernova
On 5/17/11 1:10 AM, Yousuf Khan wrote:
On 16/05/2011 6:55 PM, Sam Wormley wrote: Carbon/Oxygen core makes up at least 99% of the White Dwarf's mass. Not if they're small white dwarfs. Some white dwarfs stop at the helium stage. Take a couple of those small white dwarf husks and bang em together, and you can restart helium fusion. The examples they gave here are a 0.4 solar mass white dwarf and a 0.1 solar mass white dwarf merger. In the end, it'll probably end life as another carbon-oxygen white dwarf. Yousuf Khan Large enough stars that cannot ignite a fusion process beyond helium burning will *create* a degenerate white dwarf. No fusion process goes on in white dwarf stars unless on the surface (nova) or during collapse (supernova). |
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