elements undiscovered

[Derec]

Although I guess if we are being picky, it is possible that the heavy nucleus might still be said to exist, albeit inside an event horizon.

According to what I've read, all the matter falls into the singularity. That would mean there aren't any protons or neutrons in there any more. A black hole is supposed to have no properties at all except mass, charge and angular momentum.

Also known as the  No-hair theorem. But that refers to what is detectable from outside the event horizon. I don't think it presupposes that all matter must exist in the singularity.

- - - Updated - - -

If you have a very massive black hole you can cross the event horizon and still be alive because the tidal forces are weak enough. So obviously there are protons and neutrons.

And bookshelves.

 

[repoman]

What happens in the different layers of a neutron star can't be directly detected, can it?

I think that only neutrinos can be emitted from those layers and pass mostly unimpeded to us. Are any neutron stars close enough to find anything useful?

We have learned about our sun through neutrinos.

This makes me wonder if neutron star quakes (forgot exact term) happen when there is a sharp phase change in one or more of the layers of it.

 

[Bomb#20]

Eris. Yes, we'd have to call it the tenth planet. Apparently some astronomers thought that would be a bad thing.

There are a lot of objects like Pluto and Eris. The options were either increase the number of planets to hundreds, make up a new category and put Pluto in it, or make up a new category and grandfather Pluto in as a planet for sentimental reasons even though it doesn't really belong.

But there probably aren't a lot of objects like Pluto and Eris. There may well only be the two; and if there are more there are probably only a few more. As you get further from the sun it gets less and less likely for debris to hit other debris and accumulate into big balls, so the typical size of objects is just going to keep going down. There was really nothing stopping the IAU from adopting a fourth option -- defining an arbitrary cutoff and saying anything bigger than, say, 1000 miles in diameter, is a planet and anything smaller is an asteroid -- except unwillingness to come out and say openly what they must surely all have known perfectly well, which is that astronomical objects form a continuum, not discrete categories like physics, chemistry and biology have. The winning faction was making believe that their taxonomy could be less arbitrary than was really possible -- there just isn't any rational basis for claiming Pluto is less similar to Mercury than Earth is to Neptune. "Planet" is not a natural category like "deuterium"; it's an imposition of the human mind on nature, like "microwave".

Plenty of serious astronomers have proposed the "1000 km radius" rule for the definition of "planet". And that's a fine definition too; but the "1000 mile diameter" definition is better because it's more up-front about being completely arbitrary. Have you seen "The Englishman who went up a hill and came down a mountain"? It's based on the British government having officially defined "mountain" as a hill over 1000 feet high. That's the kind of distinction the planet/asteroid distinction is.

 

[James Brown]

But there probably aren't a lot of objects like Pluto and Eris. There may well only be the two; and if there are more there are probably only a few more.

It's a few more than that.

 List_of_trans-Neptunian_objects

Most haven't had their diameters resolved yet, but I count seven that are greater than 1000 km.

 

[Bomb#20]

But there probably aren't a lot of objects like Pluto and Eris. There may well only be the two; and if there are more there are probably only a few more.

It's a few more than that.

 List_of_trans-Neptunian_objects

Define "like". They are like Pluto and Eris in some respects and unlike them in other respects -- in particular, they're a lot smaller than Pluto and Eris.

Most haven't had their diameters resolved yet, but I count seven that are greater than 1000 km.

If astronomers object to having seven more planets, that would be a reason to set the arbitrary cutoff higher than a diameter of 1000 km. The proposal I saw was to set the cutoff at a radius of 1000 km. Then it's just Pluto and Eris.

 

[repoman]

This is a good blog for finding planet 9 that has responses in the comments by Mike Brown(!)

http://www.findplanetnine.com/p/blog-page.html

look for the comments by jehochman, they are interesting.