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The Astronomy Thread 
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Post Re: The Astronomy Thread
GeoModder wrote:
Mjolnir wrote:
Ammonia was thought to be a major component of Earth's atmosphere early on, but more modern models lack it. Ammonia's relatively reactive and unstable (as is methane, also considered a candidate), so N2, CO2, CO, and H2O is a more likely composition, with a good bit of SO2 and H2S from volcanism...basically a wetter Venus. Early enough, there would have been some H2 as well. The methane/ammonia-rich atmospheres of the original Miller-Urey experiment are not likely (though the results are pretty much the same as long as there's not much free oxygen).


Do you happen to know the 'frostline' for ammonia in the Solar System? In the current era that is?


I've looked for that kind of information before, and not had any more luck than icekatze.

It's notable that Titan has a substantial amount of methane in its atmosphere, enough for a hydrological cycle, but pretty much no ammonia...but a great deal of nitrogen, which probably came from ammonia. And ammonia ices were found on Charon, though they may have been deposited by an impactor. It's also not just a matter of ammonia being stable...ammonia is highly miscible with water, while methane is not, so it may tend to stay locked up in water ices. That would make it relatively easy to miss or underestimate, especially if it gets destroyed in or escapes from surface ices.


Sat Dec 12, 2015 3:06 pm
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Post Re: The Astronomy Thread
Miss or underestimate (ammonia)... reminds me of this expression: There's only minite amounts of it, but what is minite when you consider the atmosphere of a gas giant (Jupiter and Saturn). :)

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Sun Dec 13, 2015 4:06 am
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Post Re: The Astronomy Thread
hi hi

Here's an interesting one: Most Luminous Supernova Ever Recorded.

ASAS-SN-15lh, at its peak, put out 50 times more light than the entire Milky Way galaxy, which is twice as bright as the previous record holder.


Thu Jan 14, 2016 6:45 pm
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Sun Jan 17, 2016 2:12 am
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Post Re: The Astronomy Thread
EVIDENCE FOR A DISTANT GIANT PLANET IN THE SOLAR SYSTEM

Sorry for the capslock, just copied it. Have read about that on a German news site and although its one of many theories about such a 9th (or 10th) planet, its the first one I have heard in a while.

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Wed Jan 20, 2016 4:55 pm
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Post Re: The Astronomy Thread
I personally think they're trying to see patterns in what are essentially random numbers. It's really hard to believe that a >= 10 Earth-mass planet in our system could still remain undetected. People spent a lot of time looking for Nemesis, and all they found were Kuiper Belt objects.

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Wed Jan 20, 2016 5:10 pm
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Post Re: The Astronomy Thread
hi hi

Sure it is possible that there's a large planet out beyond Neptune, but I'm not going to hold my breath on this one. Finding a large planet out there might help support the nice model of solar system formation, but WISE did a pretty comprehensive search for large bodies in the outer solar system and didn't find anything.

If they do find solid evidence of something, it will surprise a lot of people.


Wed Jan 20, 2016 5:47 pm
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Post Re: The Astronomy Thread
Emphasis during the observatory to search for alleged planet.


Wed Jan 20, 2016 9:30 pm
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Post Re: The Astronomy Thread
http://arxiv.org/abs/1512.02652
A new submm source within a few arcseconds of α Centauri: ALMA discovers the most distant object of the solar system


Sun Jan 31, 2016 9:48 am
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Post Re: The Astronomy Thread
hi hi

In my view, Mike Brown just gets less and less credible, every time I read his work. He unambiguously slams the ALMA results, and then, just a couple weeks later, claims to have found his own massive planet in the outer solar system. And without any confirmation of its existence, goes on to call it the most planet like planet there is, an ex post facto justification for his own definition of what makes a planet.


Sun Jan 31, 2016 10:22 am
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Post Re: The Astronomy Thread
http://gizmodo.com/holy-shit-scientists ... 1755465297

According to this scientists have, for the first time, confirmed the existence of gravitational waves. Gravity generators when?


Thu Feb 11, 2016 10:15 am
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Post Re: The Astronomy Thread
hi hi

I had heard about the LIGO rumors a little while ago, and I'm hoping those results can be independently confirmed. Although, as super important as this discovery is, I doubt we're any closer to making gravity generators. This confirms what we already suspected, so it probably won't change everything.


Thu Feb 11, 2016 11:35 am
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Post Re: The Astronomy Thread
Gravitational waves are so well-established in theory that I think the shocking development would have been if the experiment had failed to detect them.

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Thu Feb 11, 2016 1:24 pm
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Post Re: The Astronomy Thread
Correct me if I am wrong but all I got from the development is that they actually 'proved' that the gravitational waves travel with a certain speed which disproves the neutonian belief that gravity is instantaneous.

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Thu Feb 11, 2016 5:14 pm
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Post Re: The Astronomy Thread
Not exactly. Gravity waves are predicted by Einstein's model of gravity, which is about a hundred years old at this point. Because gravity waves are so hard to detect, we haven't been able to directly demonstrate that part of the theory until now. However, gravity waves have already been indirectly demonstrated by the rate at which close-orbiting massive stars spiral in towards each other. So while this is an important scientific finding, and these gravity wave detectors can be used to tell us about black holes and other very massive objects, this is not a "discovery" or a new development, just a direct confirmation of what General Relativity tells us about how gravity works.

PBS Space Time has good videos explaining the finding and about gravitational waves in general.


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Post Re: The Astronomy Thread
icekatze wrote:
Although, as super important as this discovery is, I doubt we're any closer to making gravity generators.
Yeah, I suspect that the Higgs is what moved that needle, not Gravity Waves. We already had spectroscopic evidence from a case of gravitational lensing + red-shift-difference from a rapidly spinning red dwarf to demonstrate that moving masses can gravitationally transmit energy.


Thu Feb 11, 2016 10:44 pm
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Post Re: The Astronomy Thread
hi hi

This one is pretty exciting: 1.3 to 3 earth mass planet found orbiting Proxima Centauri in the Goldilocks zone.

I heard some rumors about this one a few days ago, but it sounds like Kepler went ahead and backed up the earlier observations, so there's a pretty strong chance that it's the real deal.


Wed Aug 24, 2016 11:52 am
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Post Re: The Astronomy Thread
Unfortunately Proxima Centauri is quite an active flare star. :(
And what happened with the Alpha Centauri Bb claim back in 2012? The article jumps from Epsilon Eridani b to Proxima without even mentioning it!

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Wed Aug 24, 2016 12:53 pm
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Post Re: The Astronomy Thread
GeoModder wrote:
And what happened with the Alpha Centauri Bb claim back in 2012? The article jumps from Epsilon Eridani b to Proxima without even mentioning it!

As I understand it, the methods used to detect αCenBb were called into question and then essentially demonstrated as inadequate; even the discoverer agreed that it probably doesn't exist.

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Wed Aug 24, 2016 1:37 pm
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Post Re: The Astronomy Thread
hi hi

Blarg... I misread the article. Kepler wasn't the team that provided the second opinion, rather it was a group of Earth bound telescopes. Talk about an embarrassing reading comprehension fail. :cry:

Still, it does seem like the data is pretty robust.


Wed Aug 24, 2016 2:52 pm
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Post Re: The Astronomy Thread
GeoModder wrote:
Unfortunately Proxima Centauri is quite an active flare star. :(
Given the proposed year, the planet should probably be tidally locked, greatly reducing the difficulty imposed by flares. Just move a bit closer to the equator (which in this case would be the plane perpendicular to the vector running between planet and star), and you have more atmosphere between you and the star, thereby producing something of a goldilocks zone on the planet (specifically, the temperate area with sunproximalight).

I imagine that the wind currents are impressive. Supposing that it is tidally locked, I'd expect a generalized high-level movement towards the cold side, and low-level flow towards the hot side, producing a decently gentle temperature gradiant in the "dawn-torials". Of course, if there's neither bulk atmosphere nor bulk sea/ocean, then this is bunk and it's likely to be the same half-char/half-raw meatloaf that you'd normally expect from tidal locking; and possibly the same if two semi-fixed weather fronts dominate the atmosphere, instead of a generalized mid-level mixing trend.


Wed Aug 24, 2016 3:54 pm
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Post Re: The Astronomy Thread
hi hi

If it is more massive than Earth, I would think it is more likely to have an atmosphere than not. Granted the sample size of our own solar system has repeatedly proved to be a poor indicator of what other star systems are like, but if it's massive enough to retain an atmosphere, it just needs to find one somewhere. ;)


Wed Aug 24, 2016 8:57 pm
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Post Re: The Astronomy Thread
And while Proxima Centauri is a Red Dwarf, at that distance solar wind may still have blown all volatile elements of the atmosphere away. So we run into another problem.
A planet? Yes.
(Liquid) Water? Possibly.
Life? Very unlikely.

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Thu Aug 25, 2016 12:11 am
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Post Re: The Astronomy Thread
Arioch wrote:
GeoModder wrote:
And what happened with the Alpha Centauri Bb claim back in 2012? The article jumps from Epsilon Eridani b to Proxima without even mentioning it!

As I understand it, the methods used to detect αCenBb were called into question and then essentially demonstrated as inadequate; even the discoverer agreed that it probably doesn't exist.


Ah, I missed that news.

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Thu Aug 25, 2016 6:16 am
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Post Re: The Astronomy Thread
hi hi

I'm not sure we know enough about the stellar winds from small stars to say just how problematic they are. If there are studies out there about stellar winds from red dwarf stars, I haven't been able to find them anyways. I've seen studies that show how massive, high temperature stars have higher velocity, more energetic stellar winds than our own; and I've seen studies where people assume Sun-like stellar winds for estimating the effect of red dwarfs on their planets. But it seems like actually measuring solar winds of stars the sun's size or smaller is difficult to do optically.

I guess that's just another uncertainty to deal with until we get better measurements.


Thu Aug 25, 2016 4:09 pm
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