Comments on: Spinning white dwarf bombs may lurk the galaxy

By: Joseph G

Joseph G — Wed, 21 Sep 2011 18:00:40 +0000

@29 Gary Ansorge: I’ve been wondering where all the ejected stellar planets are and if there are enough of them to account for part of our dark matter problem. They’d be really hard to spot, even if within a light year of us(very cold). It seems to be a common process as solar systems form, as in this article,,,

Now there’s an interesting question – how far above absolute zero (well, the apparent microwave background temp, which is pretty darn close – what is it, like 4 or 5 kelvin?) would the average temperature of the surface of a planet like Earth (with a molten mantle and volcanism) be in interstellar space? And how far away could such a planet be detected?

By: Messier Tidy Upper

Messier Tidy Upper — Wed, 21 Sep 2011 15:35:28 +0000

Having just given a talk on supernovae types , historical examples and Milky Way candidates earlier tonight .. I wish this had been posted earlier!

Still great write up and interesting theory.

@33. Mike Torr asks : “Now I can actually start reading this blog again.
So… did I miss anything during the dark ages of truncation?”

You do know you can just keep paging down through the ” Older Entries” button don’t you?

@35. Ken : “Phil, I have to wonder, where did that 1.5 solar masses number come from?”

I think you’ll find it came from the calculations of a bloke named Subrahmanyan Chandrasekhar, who worked out the limits of what mass a white dwarf can carry and had the Chandrasekhar limit named in his honour for it.

(Click on my name for more info. via the usual fountain of all wisdom.)

@30. VinceRN :

“Ain’t the universe cool? We just keep discovering new stuff like this. The more we know, the faster we learn new stuff.”

Yup indeed. But also the faster we learn that what we thought we knew is more complicaticated than that and learn that we not have had a full understanding of the things we *thought* we knew too.

By: Ken

Ken — Wed, 21 Sep 2011 15:33:50 +0000

Phil, I have to wonder, where did that 1.5 solar masses number come from? Did it come simply from observing white dwarves and noting that there were none with over 1.5 solar masses? If so, is it now possible the number is overly high, and that smaller stars could also go supernova? Like, say, Sirius B with 0.98 solar masses, well within 100ly of Earth?

By: CraterJoe

CraterJoe — Wed, 21 Sep 2011 14:21:11 +0000

@Mike Torr. Truncation? Whatever do you mean…I can’t see how…you…have experienced…of the sort?

By: Mike Torr

Mike Torr — Wed, 21 Sep 2011 11:07:33 +0000

Hooray! Entire posts in my RSS feed! Now I can actually start reading this blog again.
So… did I miss anything during the dark ages of truncation? :-\

By: TMB

TMB — Wed, 21 Sep 2011 05:11:14 +0000

@12, 13, 16: The uniformity of SNIa is mainly empirical, not theoretical – for every one where we already know the distance, they lie in a narrow range. Moreover, what variation there is correlates tightly with the overall timescale on which the SN fades, so it can be corrected for to make an even narrower range. Which brings up the point that we already know that there is some variable that can change from SN to SN – whatever it is modulates both the luminosity and the fading time. The general hypothesis has been that it is stochastic variations in the amount of 56Ni that ends up getting fused during the explosion, but maybe it is in fact the mass of the progenitor.

By: ophu

ophu — Wed, 21 Sep 2011 04:44:51 +0000

Explodey? Is that highly technacious termage?

By: VinceRN

VinceRN — Wed, 21 Sep 2011 04:17:34 +0000

Ain’t the universe cool? We just keep discovering new stuff like this. The more we know, the faster we learn new stuff.

By: Gary Ansorge

Gary Ansorge — Wed, 21 Sep 2011 03:56:57 +0000

Seems an elegant solution to the problem of no observed hydrogen.

I’ve been wondering where all the ejected stellar planets are and if there are enough of them to account for part of our dark matter problem. They’d be really hard to spot, even if within a light year of us(very cold). It seems to be a common process as solar systems form, as in this article,,,

http://content.usatoday.com/communities/sciencefair/post/2011/09/study-solar-system-ejected-giant-planet-early-on/1?csp=Tech

Gary 7

By: Grand Lunar

Grand Lunar — Wed, 21 Sep 2011 01:02:38 +0000

This may add a twist to “Death from the Skies”!
Perhaps a sequel may be in store?

“The research I mentioned at the top of this post was theoretical — it’s hard to get a white dwarf into the lab”

Not so hard for the Time Lords!

By: Jonathan Lubin

Jonathan Lubin — Wed, 21 Sep 2011 00:01:39 +0000

Phil, four centuries ago, Newton had to wait over thirty years to get born. Even 350 years ago was only 1661, well before everything fell together for him. So you have to say, “ using math Newton invented three plus centuries ago”.

By: Paul

Paul — Tue, 20 Sep 2011 22:26:03 +0000

I think there’s a “your mom” joke in here somewhere.

By: Wzrd1

Wzrd1 — Tue, 20 Sep 2011 22:20:35 +0000

See the above link. They talk about a “hole” knocked in the wave and nebula from the companion star.

By: Dragonchild

Dragonchild — Tue, 20 Sep 2011 22:08:57 +0000

What I’m wondering is what happens to the supernova shock wave if the stars are close together. I’d think in most of these systems the younger star is sufficiently far away to have a negligible effect on the supernova, but if they’re really close together, would the gravity of the younger star make a “dent” in the shock wave?

By: Wzrd1

Wzrd1 — Tue, 20 Sep 2011 20:29:49 +0000

@Larian Le Quella #22:
Referenced off that site is a nice one showing evidence for the survival of the companion star.
http://blogs.discovermagazine.com/80beats/2011/04/28/tychos-supernova-went-boom-after-slurping-up-some-of-its-neighbor/

By: Larian LeQuella

Larian LeQuella — Tue, 20 Sep 2011 20:13:55 +0000

@#16, amphiox, you hit on my first question too!

#19 CraterJoe, check out this: http://astronomy.stackexchange.com/questions/1165/what-happens-to-the-neighboring-star-of-a-type-ia-supernova/1167#1167

By: Wzrd1

Wzrd1 — Tue, 20 Sep 2011 19:53:38 +0000

@ TStein #13, you forget the root cause of the type 1a supernova, it is a core explosion, not the outer layers fusing. The core is compressed sufficiently for the temperatures and pressures to reach the carbon fusing point, causing a runaway fusion reaction of carbon and other elements present in the core in a matter of seconds. That releases such a great impulse of thermal energy that it unbinds the star totally.
Hence, the same amount of energy is released, regardless of the outer layer being more massive by a modest amount, though more gas would be accelerated out, the larger amount would not be that easily detected. You’re talking the difference between 1.38 solar mass and maybe, to be generous, 1.5 solar masses. To be honest, I doubt one would get as high as 1.5 solar masses though.

By: Wzrd1

Wzrd1 — Tue, 20 Sep 2011 19:30:10 +0000

@ Ceramicfundamentalist #4, nope. Those would become Kerr black holes.
http://en.wikipedia.org/wiki/Kerr_black_hole
Once an event horizon forms, it’s a black hole.

By: CraterJoe

CraterJoe — Tue, 20 Sep 2011 18:52:08 +0000

So, what happens to the other star when the first one goes boom?

By: Erika

Erika — Tue, 20 Sep 2011 18:42:05 +0000

This is just too cool.

By: X

Tue, 20 Sep 2011 18:33:24 +0000

I find it pretty hard to believe that the negligible amounts of hydrogen being accreted onto a WD SN progenitor would be observable. They would be instantly wiped out during the detonation phase. The paper doesn’t mention any such mechanism, although it does suggest looking for the SN shock interacting with the planetary nebula of the binary partner.

By: amphiox

amphiox — Tue, 20 Sep 2011 18:22:24 +0000

re @TStein #13;

I’m also curious how this potential variance in luminosity affects the use of these supernovae as standard candles.

By: Chris

Chris — Tue, 20 Sep 2011 18:08:25 +0000

@7 Thomas
You are right. It’s the electron degeneracy pressure.

By: DukeTG

DukeTG — Tue, 20 Sep 2011 17:31:13 +0000

I believe any mention of centrifugal vs centripetal is required by law to include a link to this XKCD comic:

http://xkcd.com/123/

By: TStein

TStein — Tue, 20 Sep 2011 16:54:52 +0000

Naively, I would think that allowing the star to pack on more weight then the limit would increase the variance in the luminosity. Some stars could spin up faster packing up more material and have a longer delay to they explode. Others would have less material to pack on spin up slower and explode faster. Therefore the first stars to explode this way will be possibly be dimmer since they have less material to explode. (The more massive ones take longer to spin down)

Obviously, this is way too simplistic of a model. I am curious, though, if there is enough information to try to model this better and if there might be someone out there doing it.