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A word from GeoCities:

Timescales in open, flat, and very large closed universes

   This timeline of the future of our Earth, sun, and universe was derived mostly from a variety of sources on the web, as well as a few print publications. I list the sources below (footnotes in years column). This is largely an updated and much more complete version of the timeline found here. That page also had a table listing information relating to a Big Crunch. I have not included that table here, in light of recent discoveries and growing consensus that we live in an open universe. In fact, some of the later dates may come to change significantly if evidence of a long-range gravitational repulsive force holds up.
   Some of these events preclude others; e.g. if protons decay around 10¹⁷ years, there will be no Hawking decay of matter later. As with all predictions, those events closer to the present can be considered to be known with greater reliability. However that is not strictly true here, since this timeline is a conglomeration of events derived using different methodologies and different levels of knowledge. Nevertheless I consider it to be a scientifically accurate indicator of Things to Come.
   A brief reminder: 1 million = 10⁶ = 1,000,000. 1 billion = 10⁹ = 1,000,000,000. 1 trillion = 10¹² = 1,000,000,000,000 = 1 million million. (The U.S. federal debt is around $5.5 trillion!!!)
   I'm looking for info on how long it will take a terrestrial planet to lose its atmosphere, or if gas giants will eventually evaporate (diffuse) away. Anyone know?
   The first few events are astronomy-related. I hope you enjoy reading this.

Future Time (years after A.D. 2000)	Tentative Event
10,000 years¹⁸	Our sun exits the local interstellar cloud it is currently passing through. (See diagram at reference #18 webpage, below.)
12,900 years¹	Earth's axis has precessed 180°, giving us a whole new North Star.
27,700 years	The southern hemisphere binary Alpha Centauri, or Rigel Kentaurus (now 4.35 light-years distant, with an apparent magnitude of -0.29), will reach a minimum distance from Earth of 2.84 light-years and should then be the second brightest 'star', with an apparent magnitude of -1.2.
59,000 years	Sirius A (Alpha Canis Majoris, aka the Dog Star), has an apparent magnitude of -1.46 but because of the relative motions of this star and the Sun then this should rise to a maximum value of -1.67. Sirius is now 8.64 light-years distant and has a luminosity 26 times greater than that of the Sun.
100,000 years¹⁰	The Orion Nebula complex, including the Horsehead nebula, disperses away.
300,000 years¹⁵	Long-dead spacecraft Pioneer 10 passes within 3 LY of Ross 248, 10.3 LY away.
1-1.4 million years^16,17	Gliese 710, a red dwarf star currently 63 LY away, swings in to within 62,000±9,000 AU (<1 LY) of our sun. No danger to us, except for some dislodged Oort Cloud objects.
1,250,000 years²	Delta (d) Scuti, prototype of a whole class of rapidly pulsating variable stars, takes the helm as the brightest "star" in the northern sky.
1,550,000 years²	Gamma (g) Draconis, aka the orange giant Eltanin star (the presently 2nd-magnitude nose of the constellation Draco), becomes the sky's brightest star, as bright as today's Sirius.
1.7-2 million years¹⁵	Pioneer 10, if still intact, passes near Aldebaran, 71 LY distant.
3,500,000 years²	Omicron (o) Herculis becomes the brightest star when it swings in from 350 to about 45 light-years from our sun.
4,600,000 years²	Beta (b) Cygni, aka Albireo or the beak of Cygnus, takes the brightest-star title. Depending on whether it's a true binary and its orientation to us, it could appear to the naked eye as a tightly-bound 2nd-magnitude blue star around a zero-magnitude gold star.
15 million years	The Solar System will reach the minimum distance of 27,600 light-years (perigalacticon). It's in the outer regions of our Milky Way galaxy, orbiting at a mean distance of 29,700 light-years with an orbital eccentricity of 0.07. The present distance from the center is 27,700 light-years.
40 million years^5,6	Phobos, its orbit slowed by tidal forces resulting from orbiting Mars faster than Mars rotates, falls into Mars. (Future human intervention might be able to prevent this.)
100 million years¹¹	The Dwarf Sagittarius galaxy, about .1% the size of our galaxy, passes through the Milky Way again.
500 million years¹⁴	Due to increasing solar temperatures, enough carbon dioxide (CO₂) is absorbed and trapped as limestone that plant life, and by extension animal life, dies out.
750 million years¹²	The Dwarf Sagittarius galaxy, torn and stretched, gets absorbed into the Milky Way.
1-2 billion years^3,14	The sun's luminosity has increased enough to evaporate Earth's oceans and sterilize the planet. The water vapor that was our oceans escapes into space. Mars slowly becomes relatively more hospitable.
3-7 billion years^3,8,12,13,19	The Milky Way and Andromeda galaxies collide and merge, eventually forming a giant elliptical galaxy. Supernovae explosions may occur so frequently as a result that the night sky may be bright enough to read by.
5 billion years^3,5	Sun leaves main sequence, swelling into a red giant. In time, the strong solar wind and decreased solar mass will push Earth's orbit out nearly to where Mars' is today.
7 billion years^3,5	The sun, a red giant nearly as large as Earth's orbit, now puts out enough heat to melt the ice on Jupiter's moons Callisto, Ganymede, and Europa. Earth's crust is totally molten and featureless.
10 billion years^12,19	Two more of the Milky Way's satellite galaxies, the Large and Small Magellanic Clouds, merge into it.
35 billion years⁷	The sun evolves from a white dwarf into a "dead" black dwarf.
50+ billion years⁵	Assuming the Earth-moon system is still intact, Earth becomes tidally locked with the moon. The lunar month and Earth day are now both equal, about 50 present days long.
100 billion years^3,4	Large galactic clusters evaporate galaxies through chaotic interactions.
100+ billion years³	Over the next few trillions of years, galactic clusters will coalesce into "supergalaxies."
1 trillion years^3,4	Stars cease to form from nebulae; all massive stars have become either neutron stars or black holes.
10 trillion years³	The longest lived of stars shining today, red dwarfs, use the last of their fuel and become white dwarfs. For a few billion years at the end of their lifetimes, they may have appropriate luminosity & temperature to allow for life on nearby planets.
10-100 trillion years^3,4	Universal hydrogen reserves are drained. The last of the red dwarfs die out. All star production shuts down forever, and the universe goes dark.
10^15-17 years^3,4	Stellar collisions and near-misses detach dead planets from dead stars.
10¹⁶ years⁹	Lone stars are occasionally formed by the collision of brown dwarfs.
10¹⁷ years⁴	White dwarfs cool to black dwarfs at 5° K. Proton decay (if any) will keep dwarfs at this temperature for 10³⁰ years.
10^19-20 years^3,4	Dead stars (brown & black dwarfs, and neutron stars) and planets evaporate from supergalaxies via chaotic interactions. (90-99% of all stars will evaporate; 1-10% will collect in galactic centers to form gigantic black holes).
10¹⁹ years⁴	Neutron stars cool to 100° K.
10²⁰ years³	Up until now, two brown dwarfs would on rare occasion merge to form a red dwarf. Beyond this time they're simply scattered way too far apart.
10²¹ years⁹	One-solar-mass black holes begin to evaporate as the cosmic background temperature becomes cooler than them.
10^20-24 years^3,4,9	Orbits of planets and close binary stars decay via gravitational radiation.
10²³ years⁴	Dead stars evaporate from supergalactic clusters. (Black dwarfs are at 5° K and neutron stars at 100° K due to proton decay; background radiation has cooled to 10^-13° K.)
	At this stage matter consists of about 90% dead stars, 9% black holes and up to 1% atomic hydrogen and helium.⁴
10^25± years³	Any remaining dead stars and matter still in orbit around galactic centers spirals in from orbital gravitational decay.
10²⁵ years³	If dark matter can be accounted for with WIMPs (weakly interacting massive particles), black dwarfs will accrete them. WIMP annihilation inside black dwarfs can keep them heated to 64° K for around 10³⁰ years.
10³⁰ years³	Black holes accrete remaining black dwarfs & neutron stars at the galactic level.
10³⁰ years⁹	10⁶-solar-mass black holes begin to evaporate as the cosmic background temperature becomes cooler than them.
10³²⁺ years^4,9	Protons decay (according to SU(5) GUT).
10³²⁺ years^4,9	Dead stars evaporate via proton decay (GUT). Neutron stars pass through a brief white dwarf stage as neutrons & electrons lose degeneracy, before degrading to hydrogen ice and evaporating.
10³³ years³	Black holes accrete remaining black dwarfs & neutron stars at the galactic cluster level.
10³⁴ years⁴	All carbon-based (indeed, atom-based) life forms become extinct due to a lack of atoms.
	At this stage most matter in the universe is in the form of e^-, e⁺, n,`n, g (electrons, positrons, neutrinos, antineutrinos, & photons).⁴
10³⁵ years⁹	10⁹-solar-mass black holes begin to evaporate as the cosmic background temperature becomes cooler than them.
10⁴⁵⁺ years^3,9	Virtual-black-hole mechanisms in quantum gravity allow protons to decay.
10⁶⁵ years⁴	Ordinary matter liquefies due to quantum tunneling.
10^65-67 years^4,9	Solar mass black holes evaporate via Hawking process.
10^73-85 years^4,9	In closed and flat universes (respectively), most e⁺ and e^- form positronium with atomic radii far larger than our present-day universe. (In open universe most e⁺ and e^- remain free.)
10⁸³ years³	Million-mass black holes (10⁶ M_sol) evaporate via Hawking process.
10⁹⁹ years^3,4	Galactic mass black holes (10¹¹ M_sol) evaporate via Hawking process.
10¹⁰⁶⁺ years³	Some positronium formation and decay occurs in an open universe.
10¹¹⁷ years⁴	In flat and closed universes, positronium decays via cascade, releasing 10²² photons per positronium atom.
10^117-141 years^4,9	Supercluster mass black holes (10¹⁷ M_sol) evaporate via Hawking process.
10¹²² years⁴	Protons decay via Hawking process (if not from SU(5) GUT or other).
10^140-150 years⁹	Tunneling between different vacuum states in the electroweak theory allows protons to decay.
10^10-1000?? years⁹	A cosmological phase transition reconstructs the universe, rewriting the laws of physics, changing universal constant(s), and/or collapsing a spacial dimension.
10¹⁵⁰⁰ years⁴	If ordinary matter survives decay via GUTs or Hawking process (rather unlikely), it decays into iron.
: :	: :
10^10²⁶ years⁴	All iron collapses into black holes. The universe is huge, empty, and desolate beyond imagination.

Based on info from:
¹ASTR 103: Figures for Supplement 1., Fig. 1.7.
²"Lanterns Along the Sun's Way" by Fred Schaaf, Sky & Telescope, Aug. 1998, p. 98.
³"The Future of the Universe" by Fred C. Adams & Gregory Laughlin, Sky & Telescope, Aug. 1998, pp. 32-39.
⁴Table 10.2 in The Anthropic Cosmological Principle (pp. 653-4) by John D. Barrow and Frank J. Tipler, and Anders Sandberg's Timescale.
⁵[sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/8).
⁶A. T. Sinclair (1989, Astronomy & Astrophysics, vol. 220, p. 321).
⁷The Observatory: Stars.
⁸AstroFile -- Future Fate of the Milky Way Galaxy.
⁹"The Five Ages of the Universe," by Fred Adams and Greg Laughlin, The Free Press, 1999.
¹⁰Astronomy Picture of the Day, 9/14/99.
¹¹Astronomy Picture of the Day, 2/16/98.
¹²A Tourist's Guide to the Milky Way.
¹³Astrophysicist Maps Out Our New Galaxy.
¹⁴Date set for desert Earth.
¹⁵Six billion miles and counting....
¹⁶Astronomy Picture of the Day, 12/11/99.
¹⁷Close Approaches of Stars to the Solar System.
¹⁸Astronomy Picture of the Day, 4/11/00.
¹⁹Lecture Notes for AST201: Normal Galaxies.

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