Recent content by Ken G

I agree that whether it has 2 solar masses or 3 shouldn't matter much, but that's why I'm wondering why those Xray sources in the globulars couldn't be a whole lot of BHs along with even more NSs. If so, the question is not so much where are the BHs, it is where are the BHs and NSs that we see...

Yes, binaries do allow conditions to keep the pulsars shining, making them more visible as with black holes. But I do think it's true that most pulsars are not in binaries (consider for example those two most famous pulsars, Vela and Crab). So there is an advantage for seeing pulsars that...

OK that's a good point, gravitational detectability can last billions of years, so one can ask how many NSs are known by their pulsing, and how many are known gravitationally. Since the Wiki says only 1/20 of known pulsars are in binaries, we see that many more of them are known by their pulses...

Do you still have any unresolved questions?

I think it is not terribly surprising that BHs are found much less often than NSs, because NSs have their own beams that you only have to be in the path of to see. So NSs don't need to be in binaries for us to discover them (and the Wiki on NSs says only 5 percent are in binaries, and it's not...

Yes that's a good way to get insight. We can even venture out of the Milky Way and look at SN 1987a, where JWST was able to find the neutron star. I'm not sure how the neutron star shows up in infrared light, but in any event, it has been seen. So we're getting pretty good at linking SNe to...

Interesting point, that with the right atmosphere the poles might be livable, but we know the atmosphere must be thinner than Earth because Earth is about the place where you get good (but not complete) sharing of heat. So if it was like Earth, and way closer to the Sun, it would be too hot...

I think if we do what @snorkack suggests, the numbers come out pretty consistent with what @Vanadium 50 got. It's often said the MW has about 1 SN per century, roughly equal numbers of core collapse and type Ia, so over 10^10 years, we can expect something like 10^8 black holes, or maybe it's...

You are exactly correct. As you saw from information above, a black hole is created when the core is above somewhere between 2.2 and 3 solar masses (no one knows the maximum neutron star mass). So one might expect any star above 3 solar masses to make a black hole. But that's not true, they...

It sounds to me like you are just talking about "main sequence stars", the core hydrogen burning phase that most stars are in. If you restrict to most stars, therefore, you get a simpler relation than the evolutionary paths of stars as they reach the late phases of their lives, and it looks a...

Yeah, that irony could be the basic reason why supernova simulations have such a tough time actually getting explosions to happen! Nature may "abhor a vacuum", but it seems to like irony even less...

That may be true in the low density chromosphere, but there is more to the question of "line darkening" (usually called absorption lines, or "Fraunhoefer lines") because most of those lines are formed in the deep photosphere where the density is very high. In very high density conditions, often...

I think another way to frame the question of "modified gravity vs. dark matter" is instead of asking "which one is what's really happening," ask simply "which one provides the simpler way to parametrize what's happening." Here we find interesting support for modified gravity in some contexts...

The key point is that collisions between particles of different mass share energy more slowly than particles of the same mass, so this is why electrons and protons can have a "temperature" without it being the same as each other. What is really meant is that in the frame where their average...

You have it backward, the fact that photodisintegrating nuclei removes energy means that support is taken away by that process, the opposite of providing "extra" support. Indeed this is the crucial aspect of the core collapse, at high enough energy scales there appear all kinds of new...