So what’s Wolf 359, chopped liver?
What about the validity of the theory that the Sun would expand and the Earth would be sucked into it and vaporize, frying us all, as per How Stuff Works.com - “How The Sun Works” - “Fate of the Sun”?
Frederik Pohl’s Hugo Award winning “Fermi and Fire” postulates just such a thing, and has the characters living (and eventually dying) at a geothermal power facility in Iceland after a full scale nuclear exchange and resulting climate change. I have a few issues with the stated dire projections of the Nuclear Winter Hypothesis, but it’s a fantastic story.
Stranger
What has Wolf 359 ever done for me? Heck, it’s fainter than can be seen from Earth by several orders of magnitude, and even if you could get in orbit of it, it’s a M6 variable that is unlikely to have any habitable zone. Now, Tau Ceti might be kind of interesting (although the system appears to be metals poor) but Sol wraps me in her warm yellow embrace almost every day in sunny Southern California, so I have a great affection for and loyalty to her.
Stranger
Is the sun massive enough to get all the way to iron? Seems to me that it’d have to be about 40% more massive to pass the Chandresekhar Limit and be able to fuse anything beyond oxygen, neon and magnesium.
I will have to check that out - thanks.
Chandrasekar’s Limit (~1.44 Solar masses) is the limit at which electron degenercy pressure is overcome by gravitational compression and the particles start violating the Pauli exclusion principle. When this occurs…well, honestly, we don’t properly know what happens when this occurs; speculation has the particles turning into a blob of pure neutrons, a quark-gluon mash, or some kind of high temperature gage boson condensate with free quarks bobbing around, or who knows what. Note that even before then and after this point the normal matter on the outer layers will continue to fuse until it condenses or is transmuted to iron, or otherwise blown off by the flaring, variable output of the fusion reactions.
Note that 1.44 Solar masses is the mass of the resultant dwarf star, not the original star from which it comes before blowing off a portion of its mass. (A dwarf that feeds off of a companion start and goes nova can conceivably lose more mass than it accreates via helium flashes.) At a somewhat higher mass (>3-4 Solar masses) the star goes supernova and blows off a significant amount of mass in a quick chain of reactions. At somewhat higher mass (depending on the composition of the star) it folds into itself and becomes a singularity.
And yes, the Sun will fuse elements all the way up to iron, albeit with increasing inefficiency as it moves up the fusion chain. At anything past the C-N-O cycle the fusion reactions are driven by rapid gravitational pressure and contraction, and are increasingly unstable, providing little luminous output.
Stranger
I don’t see how the earth would be “drawn into it”. It’s not like the sun is going to gain mass.
IIRC the theory is that the sun will expand in size to greater than the Earth’s orbit as it goes to the aptly named “Red Giant” phase.
There is also a short story called “A Pail of Air” about a family that survives after the earth is pulled out of its orbit and cools so quickly that the atmosphere solidifies on the ground. (The title is a reference to the characters scooping up a pail of liquid oxygen for breathing.)
Great posts in here, Stranger. Very informative. Thanks.
I’d like to ask a somewhat related question, now that things are expanding a bit. I know it’s really dumb and I’m missing something obvious, but I’ve never understood why winters are so cold compared to summers. Isn’t it the case that the only difference is that the hemisphere is tilted away, rather than toward, the sun? And if that tiny bit of difference in distance can make that much difference in temperature, then why wouldn’t a sunless earth degenerate to Triton temperatures in a few hours?
In winter you’re getting less solar radiance, and at a lower angle throughout the day, than in summer. And this happens across the entire hemisphere. The effects in climate are far more complex than just a difference of 47° of tilt (summer to winter) of course, but that’s the key component in seasonal variation.
Air streams, and thus, heat, don’t cross the equator much, so a loss of heat in one hemisphere doesn’t mean energy will be automatically transferred to the other side hemisphere to obtain a thermodynamic balance like it would in a simple system. Most heat is held by and transferred by ocean currents anyway. The Gulf Stream in the Atlantic and the corresponding circulatory loop in the Pacific serve to warm Western Europe and Western United States, respectively, making those areas considerably warmer and wetter than corresponding inland and easterly regions. Other geological features, along with larger global thermohaline circuits, serve to moderate the loss or gain of additional thermal radiation as the Earth wobbles its way around the Sun.
On the question of time, you’d have to perform a very sophisticated analysis to offer an accurate assessment of what would occur if the Sun totally blinked out; as atmosphere becomes drier (reducing cloud cover and resulting internal and external albedo) the emissivity of the Earth (i.e. its ability to radiate energy) will change, and as it changes, it’ll create feedback loops (probably posivite ones) that will continue to feed those behaviors. I’d suspect at some point that oceans would freeze over, which would both reduce available humidity sources and sources of environmental head, but at the same time retain head in the ocean deeps, allowing creatures to survive for a while at least. I’d guess only a few days of habitability on the surface, at best, before temperatures become so frigid that sustaining life becomes impossible. After that, nitrogen will start to freeze out (77K). Thermal loading and geothermal heat should keep the Earth well above the 2.7K microwave background for centuries if not millenia, and might prevent oxygen from liquidizing (54K) for some period of time, at least.
So, if you know anything that’s about to go down with the Sun…you’d better build yourself a shelter next to a geothermal vent and stock it well.
Stranger
Nitpick: Fusion of metals (in this context, anything more massive than helium) occurs quickly or not at all. A star’s helium-burning phase is only about a tenth as long as its hydrogen-burning phase, and iron formation occurs on a timescale of order seconds, as a star goes supernova. A white dwarf is no longer burning anything at all, and continues to glow only as long as it has leftover heat to radiate.
It’s in the stars!
What would happen if the fusion reactions in the core of the Sun suddenly stopped?
From what I’ve read, other than neutrinos, it takes a very long time for energy from the core to reach the surface of the Sun.
Well, of course in reality it is physically impossible for the sun to just stop shining. All the energy in the sun has to go somewhere.
So for the Sun to just disappear would require alien space bats MAKING the Sun disappear. Maybe they create a Dyson shell around the sun, and no visible light radiates out. Eventually though the shell will start radiating in the IR, probably not enough to keep the Earth from freezing, but maybe enough to keep the air from liquifying. Or maybe the rotate the Sun through a couple of dimensions, or maybe they do the same for the Earth, ala “Have Space Suit, Will Travel”. Or you turn the Sun into a black hole, same mass but doesn’t undergo fusion and doesn’t radiate much visible light. If you do it right lots of the energy of the Sun could be trapped under the event horizon, do it wrong and the earth will be fried by all sorts of superenergetic photons and exotic particles. Or send a rogue mass through the solar system precisely calculated to send the Earth flying out into interstellar space. But you’ve got to do this exactly right. If you just want to KILL ALL HUMANS it would be 1,000,000 times easier just to send a much smaller mass slamming into the Earth. That’s the thing, any aliens that could turn off the Sun could KILL ALL HUMANS in very simple easier ways. Maybe they want to preserve Earth for study, I suppose.
I always wonder if anyone has discovered any objects that radiate in the IR that could be Dyson shells. Maybe so-called “red giants” are Dyson shells that use most of the visible, and what we see is merely the waste heat radiating out into space.
How long would the crew of a nuclear sub survive assuming it’s completely stocked with food when the Sun goes out.
The sun is most definitely going to become a red giant. There is no question, scientifically-speaking, about that. The predicted sequence of stages for stars with mass similar to that of the sun is pretty solid. And pretty much all estimates I’ve heard for the diameter of the red giant that will be our sun have the first three planets (yep, that’s us) engulfed inside of it and Mars being planet numero uno.
If it were the Seaview, admiral Nelson would discover a passage to the central sea, and the crew would spend eternity battling mososaurs and radioactive trilobites.