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Astronomers may have found the first exomoon

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Re: Astronomers may have found the first exomoon

#81

Post by hparadiz »

delta_p_delta_x wrote: post #79
vikingerik wrote: post #77

Earlier quoted context omitted.

The other reply gave good info, but didn't quite answer this. Once an object's core acquires enough temperature/pressure/density to start protium fusion, it will continue, not burn out. The fusion itself increases the temperature, and the produced helium is denser than hydrogen, so the core compresses more under gravity thus increasing the pressure too. So protium fusion creates its own conditions to continue, so the…

Thanks; this is much more concise than I could manage. I think the key idea is fixed minimum/maximum boundaries for a lot of astrophysical phenomena—stellar protium fusion, the Chandrasekhar limit, Tolman–Oppenheimer–Volkoff limit, etc.

It should have been obvious to me (fusion duh!) that the result of the fusion is a higher density material that then increases the conditions for the reaction to take place. Both comments were immensely helpful and interesting! Thank you.

Re: Astronomers may have found the first exomoon

#82

Post by LearnYouALisp »

nullsanity wrote: post #51
walrus01 wrote: post #33

Earlier quoted context omitted.

Correct, but the link for "super jupiter" also goes to something that astronomers are fairly sure is 1.38x the diameter of Jupiter. Much less massive of course. Meaning Jupiter's diameter is not an absolute hard limit nothing can be larger than. https://en.wikipedia.org/wiki/HAT-P-1b It also orbits its star in only under 5 days, so a few theoretical visualization/renderings of it would probably be quite spectacular.

Nobody said it was, he said it was "pretty much". Y'all can't read anymore.

I mean, 40% is nearly 2x the projected area, anyway

Re: Astronomers may have found the first exomoon

#83

Post by pfdietz »

__MatrixMan__ wrote: post #53
_joel wrote: post #25

Brown dwarfs fascinate me, they can be at room temperature (range from about 2,800 K down to 250 K (roughly 2,500 °C to -23 °C / 4,500 °F to -10 °F) You could basically have a bath in a brown dwarf, sure you might not last long, but still...

The idea of a black dwarf is also pretty wild. The universe isn't old enough for any black dwarves to exist yet, but eventually the brown ones will radiate enough heat away that they're no longer held up by the vibrational energy of the atoms they contain. They'll stop being fluffy and settle into a mode where they're held up only by electron degeneracy pressure (a.k.a the Pauli exclusion principle)... it's a bit lik…

Neutron stars are held up by neutron degeneracy pressure, btw, not electron degeneracy pressure. White dwarfs stars are held up by that (even though they can be very hot; the temperature needed to "lift" degeneracy increases with the mass of the object.) Even the cores of some very large stars are electron degenerate; this is why they remain stable against the "pair production instability": there aren't any states into which newly created electrons can go, suppressing pair production.

Re: Astronomers may have found the first exomoon

#84

Post by annzabelle »

hdz wrote: post #12

A small dense planet, which orbits a star, is orbited by a larger gaseous moon. It's interesting the discovery is in Chile which has some of the best night skies, a Class 1 on the Bortle scale specifically in the Atacama Desert. Hoping to make it out there one day.

I recommend it. I'd been living in places that were a class 9 on the bortle scale, with occasional camping trips to places that were a class 5. I recently moved to the south island of New Zealand, and it's a class 4 in town and a class 1 on camping trips nearby. Completely different skies. It's rainy here though, so we don't get cloudless skies nearly as often as Chile does.

Re: Astronomers may have found the first exomoon

#85

Post by etra0 »

astrolx wrote: post #30
molf wrote: post #7

Earlier quoted context omitted.

I believe such organisations tend to do such things very intentionally :-) About ESO [1] > We are an intergovernmental organisation established in 1962 supported by 16 Member States (Austria, Belgium, Czechia, Denmark, Finland, France, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), our host country Chile and strategic partners. So Chile has a distinct s…

Exactly. Chile has a special status as host country of the observatory!

More than a special status as a host country, as far as I understand it is explicitly not a member state, hence it's separated from the rest of the flags (Which is curious because despite being the host country, it doesn't guarantee you being a member state of ESO).

Re: Astronomers may have found the first exomoon

#86

Post by ctippett »

delta_p_delta_x wrote: post #79
vikingerik wrote: post #77

Earlier quoted context omitted.

The other reply gave good info, but didn't quite answer this. Once an object's core acquires enough temperature/pressure/density to start protium fusion, it will continue, not burn out. The fusion itself increases the temperature, and the produced helium is denser than hydrogen, so the core compresses more under gravity thus increasing the pressure too. So protium fusion creates its own conditions to continue, so the…

Thanks; this is much more concise than I could manage. I think the key idea is fixed minimum/maximum boundaries for a lot of astrophysical phenomena—stellar protium fusion, the Chandrasekhar limit, Tolman–Oppenheimer–Volkoff limit, etc.

I appreciated both yours and the parent's comment. I read the shorter answer first, which was accessible enough to a layman like me that I was left wanting more, which made reading your comment immediately after all the more satisfying.

Re: Astronomers may have found the first exomoon

#87

Post by ludicrousdispla »

Foskya wrote: post #9

I guess it is more of a derivative of the question: "in which bucket should we put the brown dwarf? Is it a star or a planet?". The answer is neither of course; but since it is more closely related to stars than to planets, I'm more inclined to call this satellite an exoplanet (instead of exomoon). That being said it is still a nice finding, way more difficult to discover than "normal" exopanets.

Anybody know why the brown dwarf isn't considered a planet?

Re: Astronomers may have found the first exomoon

#88

Post by gnabgib »

ludicrousdispla wrote: post #87
Foskya wrote: post #9

I guess it is more of a derivative of the question: "in which bucket should we put the brown dwarf? Is it a star or a planet?". The answer is neither of course; but since it is more closely related to stars than to planets, I'm more inclined to call this satellite an exoplanet (instead of exomoon). That being said it is still a nice finding, way more difficult to discover than "normal" exopanets.

Anybody know why the brown dwarf isn't considered a planet?

Because a brown dwarf is a star? https://en.wikipedia.org/wiki/Brown_dwarf

Re: Astronomers may have found the first exomoon

#89

Post by ludicrousdispla »

gnabgib wrote: post #88
ludicrousdispla wrote: post #87

Earlier quoted context omitted.

Anybody know why the brown dwarf isn't considered a planet?

Because a brown dwarf is a star? https://en.wikipedia.org/wiki/Brown_dwarf

Where is the rule that says a star can't also be a planet?

Re: Astronomers may have found the first exomoon

#90

Post by askvictor »

selectodude wrote: post #14
Foskya wrote: post #9

I guess it is more of a derivative of the question: "in which bucket should we put the brown dwarf? Is it a star or a planet?". The answer is neither of course; but since it is more closely related to stars than to planets, I'm more inclined to call this satellite an exoplanet (instead of exomoon). That being said it is still a nice finding, way more difficult to discover than "normal" exopanets.

I thought we’re supposed to call them dwarf planets now. Dwarf star, dwarf planet.

Small-statured-person planets.
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