Fate of outer planets after sun ends its life cycle

1. Aug 6, 2014

Maylis

Do white dwarf planets ever die and eventually there will be no remains of the sun? What will happen to the gas giants with no sun to orbit?

2. Aug 7, 2014

Chronos

After a star enters the white dwarf phase, any planets not ejected during the red giant phase will remain in stable orbits. A white dwarf eventually cools and becomes a black dwarf, but, this has no effect on planetary orbits. It takes a very long time and our universe is not nearly old enough for any black dwarfs to yet exist.

3. Aug 7, 2014

phinds

And as a somewhat nit-picky aside, the answer to your subject line question is "the sun DOESN'T end its life cycle". Even when it turns into a black dwarf in the far distant future, that is still part of its life cycle.

4. Aug 7, 2014

Maylis

Is there anything after a black dwarf? Does that matter in the sun ever disperse and there ceases to be any remains of a sun? I'm imagining a scenario where a star eventually disperses and all it's matter disperses throughout the universe. I'm wondering what would happen to Jupiter and Saturn in a case where all the matter of the sun was gone and the ''center'' of the solar system was no more.

5. Aug 7, 2014

phinds

Interesting question. I don't know. A black hole will eventually evaporate through Hawking Radiation (at least that's currently the belief) so perhaps there's a similar mechanism for other objects, over really vast amounts of time.

6. Aug 7, 2014

puncheex

Ummmm, yes. But when the outer shells of the red giant are sloughed off, the mass of the star declines (by, perhaps, 80-90%?) and that changes the dynamics of the planets. Likely they will slow down and move to orbits farther out. Once the white dwarf is formed, its gravity is too high to allow more matter to easily leave, and from then on it has constant mass regardless of temperature, rotation or whatever else.

7. Aug 7, 2014

Staff: Mentor

More like 50% for the sun, it depends on the mass of the star.

If protons decay, then black dwarfs will disappear after a very long time. Even if there is no conventional decay mechanism (which is unclear), they might be able to decay via virtual black holes.
If they do not decay, the black dwarf will stay there forever.

All objects in an orbit will lose energy to gravitational waves, the orbits will decay and they will crash onto the black dwarf (making it hotter for a comparatively short timescale).

8. Aug 13, 2014

Flatland

Wouldn't black body radiation alone cause it to evaporate?

9. Aug 13, 2014

QuantumPion

The whole point of a black dwarf is that they are in thermal equilibrium with space.

10. Aug 13, 2014

Staff: Mentor

Once it is cold, the energy is not sufficient to emit a significant number of atoms - not even in infinite time as cooling goes too fast, assuming eternal accelerated expansion of the universe.

A proton needs of the order of 10 to 100 keV to escape to space, at a temperature of 1 meV (~12 K, still warmer than the current cosmic microwave background) this gives a suppression of (upper estimate) $e^{-10^7} \approx 0$. There is still some radiation pressure increasing the chance of an escaping particle a bit, but as soon as the black dwarf is cold, even that does not help any more.

11. Aug 19, 2014

tzimie

Cooling stops after some time in the expanding universe because of the radiation from cosmological horizons, so all solid objects will evaporate (of course, extremely slowly)

12. Aug 19, 2014

phinds

Did you not read post #10 or did you think it is wrong? Do you have any citations to back up what appears to be a personal theory?

13. Aug 19, 2014

tzimie

Of course it is not my personal theory. I read about it on this forum about 5 years ago. I will try to find a link later

UPD: weird, I can't Google it now... I even remember the number: in our expanding universe temperature will never fall below 10^-33K

Regarding post 10, in.the infinity of time it is irrelevant how low the probability is, if something can happen, it happens

Last edited: Aug 19, 2014
14. Aug 19, 2014

tzimie

15. Sep 2, 2014

Flatland

Are there any objects in the universe that is currently at thermal equilibrium with space?

16. Sep 2, 2014

nikkkom

Any interstellar meteoroid.

17. Sep 2, 2014

Flatland

So meteoroids won't show up on thermal camera?

18. Sep 2, 2014

Staff: Mentor

The ones that are between the stars probably won't, but any nearby will be warmed by the Sun.