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I am writing a story that is meant to take place after the death of the sun. However, 7.5 billion years might be a little long for most people to stomach. Is there anything that could cause the sun to turn into a Red Giant sooner?

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    $\begingroup$ Great question, and welcome to the site. I look forward to the answers, but basically your red giant occurs only when it runs out of hydrogen and helium. I suspect you will have to artificially remove it from the core somehow? $\endgroup$ – Mikey May 18 '15 at 18:16
  • $\begingroup$ Suggestion for someone more knowledgeable than me — if you somehow had an absurdly large muon beam and pointed it at the sun, could you induce muon-catalyzed fusion or something like that? $\endgroup$ – hobbs May 19 '15 at 1:28
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    $\begingroup$ Why are you (or the people) so keen to see our Sun dying? also 7.5 billion years is longer than any living organism to stomach let alone people but I have a great plan and it'll discount 0.5 billion years from Sun remaining life expectancy wanna hear it? $\endgroup$ – user6760 May 19 '15 at 6:15
  • $\begingroup$ Relevant question on physics SE: physics.stackexchange.com/questions/123569/… $\endgroup$ – Kyle May 19 '15 at 8:30
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    $\begingroup$ Something to ponder: do you even need to explain? If your characters are hyper-advanced humans then maybe they should be able to explain why the sun has gone off early; but if they've regressed to the Stone age, maybe all you need is to tell some garbled legends. $\endgroup$ – Tom Potts May 19 '15 at 8:52

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One possibility is that we're simply wrong on when the sun will go to the Red Giant phase.

Science has a good idea of how stars work, but it's not like we can actually look inside of it, or probe it to see what's going on. All of our information is secondary - it's like trying to create a 3D model of something based solely on seeing the silhouette. You can do a pretty good job, but there's also a lot of room for guesswork or mistaken assumptions.

So maybe, due to some mechanism we're not familiar with yet, we've misidentified where our sun is in its life-cycle, and it's actually a lot closer than we thought. That doesn't mean it's likely to go Red Giant tomorrow - we'll notice before that - but say, somewhere in the ten thousand to ~1 million years range is probably reasonable.

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    $\begingroup$ While it's possible the estimate is not correct, it's hardly reasonable to say "oops, we were off by 74,999,900%". Seventy five million percent is a rather unbelievable error. Astronomers are far more competent than that. $\endgroup$ – Samuel May 18 '15 at 21:58
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    $\begingroup$ @Samuel: Our predictive abilities when it comes to chaotic, turbulent systems like stars, the weather, earthquakes etc. are not very good at all. Relevant quote from Richard Feynman: "If we watch the evolution of a star, there comes a point where we can deduce that it is going to start convection, and thereafter we can no longer deduce what should happen. A few million years later the star explodes, but we [don't know] the reason." $\endgroup$ – BlueRaja - Danny Pflughoeft May 18 '15 at 22:18
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    $\begingroup$ @BlueRaja-DannyPflughoeft Moment to moment precise predictions of stars, weather, or earthquakes are difficult. The lifetime of a star is something completely different than that. It's more like predicting that there will be an earthquake in the next 1000 years or what the average climate for a region over a decade will be like. We can't predict when a single radioactive particle will decay, but we can very precisely predict when a large sample will reach its half-life. The life of the sun is like the latter, not the former. $\endgroup$ – Samuel May 18 '15 at 22:25
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    $\begingroup$ @Samuel: I'm saying the model we're using to create that estimate is possibly incomplete, thus invalidating the results. It would be nearly impossible for astronomers to screw up calculations that badly - this answer assumes something is going on they don't know about, and haven't taken into account. $\endgroup$ – Dan Smolinske May 18 '15 at 22:31
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    $\begingroup$ @Samuel: He clearly states his main concern is to make it happen in less than 7.5 billion years. So while this doesn't technically answer the question, it seems like it addresses the spirit of it. $\endgroup$ – Dan Smolinske May 18 '15 at 22:53
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Red giants come into being when a star's core becomes depleted of hydrogen. AFAIK there is no "real science" method to speed up the process, as it's directly coupled to the rate at which the star is consuming fuel; the rate the star consumes fuel is coupled to the star's mass.

An in-universe method of sciency technobabble tech could do it, depending on what exactly you have planned for your story.

Issac Asimov's story "The Last Question" eventually uses the concept of "sunpower units." I'd always imagined these as some sort of power station drawing off the helium of the star and fusing it as fast as possible.

If it works in your story, it might be an interesting story hook if the Sun was used as a fueling depot by some alien species, who used hyperspace/subspace to extract hydrogen from the core. Maybe they need to draw it from the core so they can have the fuel at the right temperature, which would explain why they're not just "scooping it" off the surface. This goes on for a while until the solar system is finally flagged as "inhabited," but by that point the damage had been done, and in a few ten thousand years the sun baloons out into a red dwarf.

If you want to give humanity the technology you can do that as well. The thing to note is that you need to use some technology to pull the helium FROM THE CORE. Pulling it from the surface won't make a difference, as surface helium doesn't get burned until way late in the sequence. Sure, it reduces the lifetime of the star, but wouldn't affect the burning rate.

If you can artificially reduce the helium in the core, maybe even have whoever is doing it dumping trash hydrogen or carbon and iron in there, you could nudge the star along the main sequence.

The only other thing I'd point out is whatever you do to the Sun you have to have MASSIVE tech to pull it off. There are 5 billion years of fuel in the core, and the sun is burning ~600 million TONS of hydrogen to helium every SECOND. In order to burn out the sun, you'll need something that can eat up 2-10x that fuel.

Smashing another sun into the Sun won't make it burn off faster, it'll actually top it off. Having a binary style star show up wouldn't work, because it draws fuel off the surface (and would cause more harm elsewhere).

If you don't want some kind of alien tech, a "realistic" sounding idea to me is having a black hole migrate into the core. It would soak up fuel while also increasing the gravity within the core. This might work in causing the hydrogen to ignite, but I'm pretty sure any black hole big enough to do this would cause other gravitational problems to the solar system. Also, I'm not a nuclear physicist, so Stephen Hawking might have problems with this suggestion.

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  • $\begingroup$ I thought helium was the product of a star's reactions, not the fuel. $\endgroup$ – DaaaahWhoosh May 18 '15 at 18:42
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    $\begingroup$ The "sunpower units" are not a device, they're a unit of measure. As in, the amount of power output by some standard sun. $\endgroup$ – Samuel May 18 '15 at 18:42
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    $\begingroup$ @DaaaahWhoosh It depends on the size of the star. $\endgroup$ – Samuel May 18 '15 at 18:43
  • $\begingroup$ @DaaaahWhoosh the product of burning is used as the fuel in the next (hotter) stage once it runs out of the first. Read up on stellar lifecycles and the red giant stage in particular. $\endgroup$ – JDługosz May 18 '15 at 19:28
  • $\begingroup$ @Samuel, I realize it's a unit of measure. But it also has to be a process of converting fuel into energy. Based on the context (stating that the galaxy expends huge amounts of "sunpower units" and only a few are captured) could imply something like a Dyson Sphere or other passive solar collection, the fact that the story is about trying to "outrun entropy" tells me that some some faster-than-standard-solar-fusion process of turning suns into usable power. $\endgroup$ – AutoDMC May 18 '15 at 19:52
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There is one "simple" way...simply pile on the mass of Hydrogen. Large stars burn hotter, and much faster than midsize or small stars, and reach the end of lifetime quicker.

How to add 10 solar masses of Hydrogen is left as an exercise for the reader.

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    $\begingroup$ Also, you'd have to speed up the Earth's rotation around it just to keep Earth at the same distance, and you'd probably even have to pull the Earth out to a higher orbit to avoid toasting it. $\endgroup$ – Atsby May 19 '15 at 2:33
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    $\begingroup$ This is the best and simplest answer that works within the framework of current scientific understanding. Although piling mass on to the sun would definitely create problems for Earth (as Atsby explained in their comment), a scenario could be imagined where the mass that is combining with the sun disturbs Earth's orbit on its way to the sun in such a way that Earth will have an orbit further out from the sun. $\endgroup$ – NeutronStar May 19 '15 at 14:56
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The Xeelee stories involve photino birds which are dark matter life forms that use dense normal matter (inside stars) to reproduce by a 3D templating process. They are making stars turn red and “old” in a few tens of millions of years, not the expected billions.

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This is not a direct answer to your question, but could provide a different explanation for the same narrative. If your overall goal is to have an Earth without a sun, it would be easier to move the Earth than to put out the sun.

For example, a rogue black hole could pass through the solar system. It doesn't pass close enough to cause direct harm to the Earth through tidal forces, but it does pass close enough to give the Earth a gravitational boost. This increases Earth's velocity such that it is above the escape velocity of the sun. Over the next year or so, the Earth travels away from the sun, until it no longer provides an appreciable amount of light or heat.

The advantage is that this could happen at any point in the future, so you wouldn't need to extrapolate out to stellar lifetimes.

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  • $\begingroup$ Indeed this has been the subject of many a sensationalist TV documentary on possibly ways life on Earth could end. Highly highly highly unlikely but still technically possible and would be difficult (if not impossible) to see coming. $\endgroup$ – thanby May 19 '15 at 18:56
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Accelerating the rate in which Hydrogen is burned off and the Sun migrates to burning helium and eventually heavier elements up the curve of binding energy is what causes the Sun or other stars to move into the Red Giant phase of their lives.

Some ideas have been discussed unthread, but perhaps the only other means of doing this would be to somehow speed up the rate at which time passes in the core of the star. There would be other noticeable effects, especially as the sudden surge in energy production and release reaches the surface (energy is generated in the core, but often it takes thousands of years to migrate to the surface. Neutrinos are the obvious exception to this), but if calibrated correctly, the hydrogen would be depleted in a few centuries or millennia, and then the "hotter" reactions involving helium would become dominant and the Sun would begin to expand.

OF course, the speeded up solar core would have pretty apocalyptic effects long before the time the Sun became a red giant, which might be what you need for your scenario.

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  • $\begingroup$ It really depends on how much you sped it up. Charles Stross has a book called Iron Sunrise where a weapon is dropped into a star that causes the core to speed up. The effect only lasted for less than a second of real time, but inside the field there was a relative time of several billion years, long enough for the core to fuse into iron. Then the field shut off and drops the iron core back into realtime, basically killing the star in an instant, causing it to go nova and destroy the planet. $\endgroup$ – AndyD273 May 18 '15 at 19:03
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A large planet or barrage of planets falling into the sun would accelerate the sun's death. This is because stars with more mass burn more brightly and more quickly.

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Red giant might be impossible, but a collision with a white dwarf could kill a star. But I think the most likely result would be a supernova and a neutron star remnant. The mass limit is only 1.4 solar masses after all. I guess you could assume either a low mass white dwarf or a collision with high enough energy to blow off much of the mass of the sun. In any case the addition of the white dwarf would allow the composition of the sun to change relatively fast and it would add heavier elements and probably blow off significant amount of hydrogen, so it would drop the lifespan.

Downside of this solution is that the "special effects" would be spectacular, quite deadly, and entirely different from the red giant you asked for. The energy released on impact would be quite lethal and even a near miss by a stellar mass object would alter planetary orbits. But if that is okay...

Actually, maybe a near miss by a stellar mass object causing the Earth to be propelled out of the solar system would be close enough for your needs. Watching as the sun shrinks in the distance and atmosphere freezes would be very close in effect to sun dying.

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The exponential dilemma might be a good bet.

lets say that there are 120 gallons per tank.

lets say that we can fill twice the gallons to the tank in the same time that we did before, a minute. So that in the first minute we fill one gallon.

1th minute 1 gallon       **1**
2nd minute 2 gallons      **2**
3rd minute 4 gallons      **4**
4th minute 8 gallons   +  **8**
5th minute 16 gallons     **16**
6th minute 32 gallons     **32**
7th minute 64 gallons     **64** = 127 total gallons, a little more  
8th minute 128 gallons              than than one tank.
9th minute 256 gallons

At this rate it took 7 minutes to fill a 120 gallon tank, the next minute will fill a whole new tank, and the next minute will fill 2 tanks

To summarize:

at the 7th minute we have a filled tank at the 8th minute we have a new filled tank at the 9th minute we have two more new tanks

Total of 4 tanks in 9 minutes, one in 7 minutes, one in 1 minute and two more in 1 minute.

this rate can be a a solution for your problem.

EDIT

2^33 = 8589934592

you can say the sun death was predicted in linear growth but that it actually is in exponential growth. Using the example from above changing a minute for a year, it will take 33 years.

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Another Asimov one: The Currents Of Space; no doubt the physics is dated, but the idea is useful.

The general concept here is that, rather than having a single collision with a massive body such as a white dwarf, there is a more continuous accretion of some kind of matter which accelerates the fusion processes.

First, note that due to the size of the sun normally a long time elapses between energy being released in the core and it being emitted from the star. This means that the changed process may have started a long time ago.

Perhaps rather than using normal hadronic matter, one might use some kind of exotic dark matter attracted to the Sun by gravitation and accreting in the core in such a way as to catalyze the fusion process.

I'll admit a problem with this line of thinking: to burn up the star faster it must lose a lot of energy. This means more of a Nova than a Red Giant.

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Peak Sun

A thousand years in the future, mankind has mastered physics to the point where we can mine the sun using force-fields and other "so advanced it looks like magic" tech. While great for allowing mankind to power their space-ships and spread throughout the solar-system (and possibly galaxy) it does rapidly advance the aging of the star. Keeping in mind that the sun is really really big, this would have to be a fairly huge mining operation, but if it's used to power, and provide matter for, a matter recombinator to terraform Mars, and other stellar bodies in the solar system it might just accelerate the "end of the sun" enough.

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    $\begingroup$ Did you mean: Star lifting? $\endgroup$ – Scott Downey May 19 '15 at 14:29
  • $\begingroup$ I'm not really surprised someone already thought of it. $\endgroup$ – aslum May 19 '15 at 14:31
  • $\begingroup$ Only problem being: that makes the sun live longer. :P $\endgroup$ – BenRW Jan 21 '17 at 22:04
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Perhaps something that the population do could cause the sun to die off a little quicker - use the fear that some people had of CERN destroying the world when it was turned on and adapt that.

Researchers in their quest for a more efficient energy source accidentally use their particle accelerator to create a stable black hole, but an unknown effect meant that the black hole was attracted to the greatest mass in the solar system - the Sun. The newly created singularity accelerated away from the Earth to reach a stable point near the Sun (or in it?) and accelerated the Suns loss of fuel.

Some of the other answers have possible rates of consumption that could be tweaked based on the size of the black hole.

Alternatively, perhaps scientists were looking for a way of opening wormholes between systems and accidentally latched our end of the wormhole into the Sun, causing the fuel in the Sun to be moved through it.

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We make a lot of studies and assumption on elements that we can see or sense. Our experiments and results are a direct product of our analysis of known elements or bodies. What if there are celestial bodies that exist that we cannot sense? These objects could be moving at great speeds, invisible and could be causing sudden demises to stars by sucking in hydrogens.

This could possibly cause the early annihilation of our beloved sun and we wouldn't even know what hit us. Or probably we realise something approaching the sun, looking at the destruction caused by it on the way and we are unable to stop it.

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Rather than trying to explain the sun misbehaving, you might invoke some handwavium time warp that propels the Earth 7.5 Billion years into the future. Or on an even smaller scale, that just transports your people, such as a slightly misconceived time machine.

I have read variants on this at least twice. In a short story (Niven?) where a hyperspace drive malfunction takes a space-liner even further into Earth's future, when the Sun has become a dwarf star. And in a Robert Charles Wilson series of novels Spin where an alien field wraps Earth and slows time down about 100-million fold for humanity compared to the universe outside. (The reason emerges later).

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