The Astronomy Thread

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Arioch
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Re: The Astronomy Thread

Post by Arioch »

That's what happens when objects get very dense; you can get very close to a large mass. The tides would probably be pretty hellacious, too.

Low-mass stars have a strange property where the puffy gas envelope of a huge gas giant crosses some tipping point and becomes compressed. Which is counter-intuitive, since you would think the new outward pressure from the fusion reactions would increase the diameter rather than shrinking it. Or maybe it's because the puffy outer layers get blown off as the process begins. But it's almost all hydrogen anyway, so I'm not sure that makes sense either.

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Razor One
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Re: The Astronomy Thread

Post by Razor One »

The universe isn't here to satisfy human sensibilities, so some counter-intuitiveness should be expected, and treated as suspect when it isn't found. ;)
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boldilocks
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Re: The Astronomy Thread

Post by boldilocks »

One day humans will sail among the stars and find it all terribly mundane and boring.
Until then, let's gape at these movies filmed by probes passing beyond where any of us can go, with a sense of childlike wonder.

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Re: The Astronomy Thread

Post by raistlin34 »

boldilocks wrote:One day humans will sail among the stars and find it all terribly mundane and boring.
Until then, let's gape at these movies filmed by probes passing beyond where any of us can go, with a sense of childlike wonder.
I´m not that confident. Between the insane amount of resources (specially fuel) it would require plus the extremely long distances...well, I don´t expect a real life Star Trek anytime soon.

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Re: The Astronomy Thread

Post by RedDwarfIV »

raistlin34 wrote:
boldilocks wrote:One day humans will sail among the stars and find it all terribly mundane and boring.
Until then, let's gape at these movies filmed by probes passing beyond where any of us can go, with a sense of childlike wonder.
I´m not that confident. Between the insane amount of resources (specially fuel) it would require plus the extremely long distances...well, I don´t expect a real life Star Trek anytime soon.
Perhaps not Star Trek.

I am reminded of Elon Musk's comments regarding the Falcon rocket landings, and how he hopes that they will become mundane rather than a huge event, because that'll mean they've become common enough not to care about.

The first sleeper/generation vessel sent to another star STL would certainly be a momentous event. If we started sending one every two years or so? People would accept it as a fact of life.
If every cloud had a silver lining, there would be a lot more plane crashes.

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Re: The Astronomy Thread

Post by icekatze »

hi hi

The two big things that determine the diameter of a gas giant is their mass and there temperature. Theoretical models suggest that Jupiter was twice as large early in its existence, and has been contracting as it cools. But thermal expansion and gravitational compression don't oppose each other in a linear manner. Jupiter would need somewhere between 50 and 75 times more mass to ignite fusion in its core.

EBLM J0555-57Ab is estimated to be cooler than some hot jupiters that have been discovered in close orbits around larger stars, suggesting that its internal fusion is so meager that it isn't doing much to counteract the much greater mass.

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Re: The Astronomy Thread

Post by GeoModder »

Imagine that, this borderline star would see the end of the universe if there was an end to it. Its fusion process is simply too 'slow' to convert enough hydrogen in time.
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Re: The Astronomy Thread

Post by Arioch »

GeoModder wrote:Imagine that, this borderline star would see the end of the universe if there was an end to it. Its fusion process is simply too 'slow' to convert enough hydrogen in time.
Yeah, the smaller the star, the longer it will last.

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Re: The Astronomy Thread

Post by RedDwarfIV »

GeoModder wrote:Imagine that, this borderline star would see the end of the universe if there was an end to it. Its fusion process is simply too 'slow' to convert enough hydrogen in time.
So... a nice place to ride out the heat death of the universe?
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Re: The Astronomy Thread

Post by GeoModder »

At the coldest star in the universe, yeah. :lol:
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Re: The Astronomy Thread

Post by icekatze »

hi hi

The latest news in the field of "It might be aliens, but in reality it's almost certainly not." Strange Signals from the Nearby Red Dwarf Star Ross 128 :P

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Durabys
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Re: The Astronomy Thread

Post by Durabys »

Okay. Everyone heard about KIC 8462852? The slowly dimming star that sometimes gets occluded by 'something' orbiting it?

Scientists tried and failed to explain the phenomenon for example by impossibly big asteroid and comet swarms or a secondary brown dwarf orbiting the primary star. All failed to explain one or two other things. For four years, people with Ph.D's and CSc's in astrophysics tried and failed to account for every strange thing that happen around the star and create an overarching theory that could explain dozens of anomalies in one theory. Nothing sticks..but it actually really being Aliens.

Well. Don't be confused anymore. Because the dimming process has now accelerated to an epxonential curve and the star will disappear within twenty years and a hundred/thousand years.

Video summary:
https://www.youtube.com/watch?v=ANSFcswnyAM

TL;DR: It truly seems that someone out there is building a star system sized Dreadstar.
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Re: The Astronomy Thread

Post by icekatze »

hi hi

Measure a star for 70 days, make predictions about 20 years in the future. I guess we'll see what happens. :P

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Re: The Astronomy Thread

Post by Arioch »

Fitting a curve to an irregularly fluctuating set of data points is 20% science and 80% bullshit. You can make the curve look like anything you want.

There could be all kinds of things going on in that system... one or more planets that came too close and were torn apart and are in the process of either falling into the star or being ejected... a chunky proplyd... any phenomenon that is not stable and is in the process of changing. Frankly, I would expect the signature of an artificial structure to be extremely regular, so I don't see how that hypothesis answers any questions.

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Re: The Astronomy Thread

Post by Krulle »

I always get suspicious if the main "result" they deliver is a video...
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Re: The Astronomy Thread

Post by Absalom »

I'd bet more on a highly variable set of flare cycles, or an orphan black hole orbited by a set of massive clouds, than aliens.

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Re: The Astronomy Thread

Post by Durabys »

And KIC 8462852 continues to be super mega bullshit. Now it has an exponentially dimming downward trend. Jesus Christ!

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Re: The Astronomy Thread

Post by Durabys »

HOLY SHIT BATMAN!

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Re: The Astronomy Thread

Post by Krulle »

Oh jezus.... We are, from a simple point of explanation, just moving relatively so, that thr accretion disc of Tabby's star is oriented such, that our view passes more and more along thr disc plane, and the angle is getting smaller.
That alone could explain it all.

Bye bye mystery.
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Re: The Astronomy Thread

Post by Durabys »

Krulle wrote:Oh jezus.... We are, from a simple point of explanation, just moving relatively so, that thr accretion disc of Tabby's star is oriented such, that our view passes more and more along thr disc plane, and the angle is getting smaller.
That alone could explain it all.

Bye bye mystery.
Accretion disc was considered two fucking years ago and left because there is no fucking IR heat up of dust happening. NONE.
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