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comment by DERPALERT

I'm fairly sure that Pluto isn't a comet

Edit: oh





asdfoster  ·  2171 days ago  ·  link  ·  

It's one of the biggest comets! Big enough that it's reached hydrostatic equilibrium and has become round, which is coincidentally the criteria required for it to be called a "dwarf planet" as well. Compositionally, it is indistinguishable from a comet, and formed in the same region as most comets (the Kuiper Belt - the same place that 67P was formed!). If it were moved closer to the sun, the ices on its surface would begin outgassing, just like a comet, however because of its larger mass and escape velocity, the gasses would be mostly bound to the surface instead of making a tail (at first, of course over time that atmosphere would escape and Pluto would lose enough mass that its atmosphere would begin to form a tail).

https://en.wikipedia.org/wiki/Pluto

am_Unition  ·  2171 days ago  ·  link  ·  

"Dwarf planet" is the new official term. Used to be "planetoid".

Things get reclassified every now and then based on how the planetary science community prefers to categorize them.

asdfoster  ·  2171 days ago  ·  link  ·  

Actually, it's all three! It's a comet, it's a planetoid, and it's a dwarf planet.... and it's a Trans-Neptunian object, a Plutoid, a Kuiper belt object, a Plutino... The list goes on and on.

https://en.wikipedia.org/wiki/Minor_planet

https://en.wikipedia.org/wiki/Pluto

am_Unition  ·  2171 days ago  ·  link  ·  

You're not wrong.

I was merely considering size, not composition. I just believe that when most people hear the term "comet", they should think of an object the size of the Rosetta comet, as that size of comet is far more abundant, at least in our solar system (and probably most).

asdfoster  ·  2171 days ago  ·  link  ·  

Well like most things in our solar system, cometary size distributions follow a power law, Pluto just happens to be at the larger, rarer end of that spectrum.

am_Unition  ·  2171 days ago  ·  link  ·  

    power law distribution

Now we're talkin'. I can see you're not a novice. Cheers!

Edit: do you work in space science?

asdfoster  ·  2171 days ago  ·  link  ·  

I do! Exoplanets are my field in particular.

am_Unition  ·  2171 days ago  ·  link  ·  

I'm plasma. Which is like, the stuff that's in my blood, I think. Right?

But seriously, no one cares about plasma. It's so far removed from the human experience that it's harder to stir up excitement. No pretty pictures, basically.

Oh boohoo, whoa is me, etc.

WanderingEng  ·  2170 days ago  ·  link  ·  

I care about plasma! Plasma is why a temporary fault on a power line (a lightning strike is a common instigator) has to be cleared by disconnecting the line. The lightning is long gone, but the overvoltage it caused creates a plasma arc that is sustained by the line voltage.

Do I have that right? I'm a utility electrical engineer.

am_Unition  ·  2170 days ago  ·  link  ·  

That all sounds correct. Plasma is more conductive than Earth's gaseous atmosphere by many orders of magnitude.

I think the arc usually forms a disconnect within 10 seconds or so, because of thermal turbulence it has helped induce in the surrounding air. Problem is, you don't want a line arcing for 10 seconds, because that can really do some damage.

Does 10 seconds sound about right? Or will it go on indefinitely? Of course, it's dependent on voltage, spacing, even geometry. I guess I mean in general.

WanderingEng  ·  2169 days ago  ·  link  ·  

From the grid side, we clear a fault like that in less than a quarter of a second. It can wreak havok when a fault lingers. But sometimes they do! There's video of a fault that lasted long enough for someone to wake up at the sound of an explosion, look out the window, grab their phone and start videoing.

My experience, which mostly comes from training on "this is why we always clear faults quickly," is a fault that remains for a few seconds eventually becomes more severe. I think it's that turbulent air you mentioned. One of the three phases will have sustained plasma, and that plasma moves around and eventually the second and third phases get involved. If the first phase wasn't enough to clear the fault, the second and third ones are.

Plasma is really interesting!

am_Unition  ·  2169 days ago  ·  link  ·  

I'm typing this while my girlfriend watches, this is like my dirty talk.

Here is what she has to say: y,k6gfhu9-ewatfrdrtqyhg6f5e478huhiiiuy

Edit: we are lol'ing together. OK, now we are cuddling

Edit 2 (the morning after): Uh. Thank you for your tolerance and clarification. :)

user-inactivated  ·  2169 days ago  ·  link  ·  

    No pretty pictures, basically.

Does neon not count?

am_Unition  ·  2167 days ago  ·  link  ·  

Oh, it absolutely does! But I couldn't find the word "plasma" anywhere on that page. There's a disconnect between personal experience and scientific literacy in this instance, just like... almost every other subject. Damn.

asdfoster  ·  2171 days ago  ·  link  ·  

Very cool! Not my cup of tea personally, sounds like the worst of E&M, fluid dynamics and atmospheric science all rolled into one. But still, always cool to see another astronomer around.

But yeah, I feel you about the lack of pretty pictures. I've got some nice plots for you to ogle, but nothing of the actual planets. Just some blobby pixelated images of their host stars.

Still, the pretty stuff is cool and generates a lot of public excitement which is always nice.

Also, I wouldn't sell your field short. I'm assuming that you're studying plasma around the sun, and those CMEs and stuff can be pretty beautiful.

EDIT: I added some stuff.

am_Unition  ·  2171 days ago  ·  link  ·  

Hey now, a little bit of magnetohydrodynamics never hurt anyone. :)

See you around!

asdfoster  ·  2171 days ago  ·  link  ·  

Well, maybe not, but I'm so used to hydrodynamics as it applies to atmospheres that adding in charges and magnetic fields just seems like it would make everything so much more complicated. You're a braver man than I to tackle it. Nice meeting you!