The universe is full of two trillion galaxies, each containing thousands of billions the stars on... <+> average, v countless more to come in the future. Yet every one of it will someday come to an end. Here"s how.

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NASA, ESA, J. Jee (University that California, Davis), J. Hughes (Rutgers University), F. Menanteau (Rutgers University and also University the Illinois, Urbana-Champaign), C. Sifon (Leiden Observatory), R. Mandelbum (Carnegie Mellon University), L. Barrientos (Universidad Catolica de Chile), and also K. Ng (University of California, Davis)

For centuries, the best questions about our universe were philosophical ones. Wherein we came from, how we acquired to it is in here, and where we were headed in the future were inquiries for poet and theologians; science had no answers because that the biggest cosmic mysteries the all. End the past 100 years, all of this has actually changed. We understand what provides up the Universe and also how it became this way. We know about the huge Bang and also have solid physics theories for what collection it up. And also we know about dark energy and also cosmic accelerations, which determines our eventual fate. However what happens once we obtain there? That"s what bill Mansley desires to know, as he asks:


When will certainly our cosmos reach the allude of preferably entropy? and what other possibilities exist because that our universe in the much future?

To number this out, let"sstart with where we space today, and also then let"s see what wake up under the regulations of physics, together we know them, as we run the clock forward into the future.


The full UV-visible-IR composite of the XDF; the greatest image ever before released the the distant... <+> Universe. In a an ar just 1/32,000,000th that the sky, we"ve discovered 5,500 i can identify galaxies, all owing come the Hubble room Telescope. Numerous the most remote ones seen below are currently unreachable, even at the rate of light, because of the relentless expansion of space.

NASA, ESA, H. Teplitz and also M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and also Z. Levay (STScI)

Our observable world is filled with roughly 2 sunshine galaxies, occupying a an ar of an are that we can access for about 46 billion irradiate years in all directions. After practically 14 billion year of cosmic evolution, virtually every galaxy is filled with tremendous quantities of heavy elements, capable of creating rocky planets, essential molecules, and the building blocks that life v each brand-new star that forms. Our own Milky Way, alone, contains roughly 400 exchange rate stars, and we"re bound together in our local group of galaxies. In in between groups and also clusters that galaxies is the expanding fabric of north space, dominated by dark energy: an power inherent to space itself. End time, however, every little thing that binds the Universe together will degeneration away.


A collection of stills mirroring the Milky Way-Andromeda merger, and how the skies will show up different... <+> from planet as the happens. This merger will occur approximately 4 billion year in the future, v a vast burst of star formation leading to a red-and-dead, gas-free elliptical galaxy: Milkdromeda.

NASA; Z. Levay and also R. Van der Marel, STScI; T. Hallas; and A. Mellinger

First come the gas, necessary for newly-forming stars. As gravitational interactions take it place, both in ~ galaxies and also between disconnected galaxies, gas clouds collapse into nebulae, which provide rise to brand-new star formation. The biggest a star-forming an ar can be is the dimension of whole galaxy: a starburst galaxy. This will take place to us around four billion year in the future, once we merge v Andromeda. What remains will be an enormous elliptical galaxy— Milkdromeda— that includes an huge number of new stars, however that has actually hardly any type of gas left. As it stands, star development hit a height in the Universe around 10-11 billion year ago, and has been declining ever since. While the sometimes gas cloud or stellar remnant will certainly remain, offering the Universe new chances because that stars, planets, and life, this is currently heavily ~ above the decline even today.


The assorted groups and clusters we deserve to see here — consisting of our local team — room all individually... <+> bound, however the an are between every of lock is expanding.

Andrew Z. Colvin / Wikimedia Commons

Every galaxy that"s a part of a bound structure, like the 60-or-so galaxies in our local group, or the ~1,000 or for this reason galaxies in the Virgo cluster, will remain bound together. Gravitation, in areas spanning countless light years across, has controlled to get over the expansion of the Universe. However, some 6 billion years ago, dark energy came to dominate the development rate of the Universe. Any structures the weren"t currently gravitationally bound when that change occurred will never become so, and instead they"ll expand away from all the other structures. The galaxies in our local team will stay bound come us, at some point merging together right into one huge one, while every the other galaxies accelerate away. By time one or two hundred exchange rate years go by, Milkdromeda will be the only galaxy visible in the whole Universe come us.


The longest-lived stars are the shortest in mass and reddest in color, and also will burn for many... <+> trillions that years. Given enough time, however, they too will go dark, together the world runs out of fuel to it is provided existing stars and create brand-new ones.

Wikimedia Commons user Fsgregs

The stars themselves, however, will continue to burn because that a long time. The world is currently 14 billion year old, however the longest-lived stars today— the low-mass red dwarfs— will continue burning with their fuel extremely slowly: because that perhaps more than 100 sunshine years. ~ that, they"ll cool and contract, becoming white dwarfs and also eventually walking dark, a procedure that might take upwards the a quadrillion (1015) years. Also at that, there will certainly still be brand-new chances for flashes, flares, and other develops of illumination in the Universe. Brown dwarfs, which themselves space failed stars, will eventually collide-and-merge v one another, giving rise to new stars if lock cross that threshold. Ghost star or white dwarf merger will create a quick burst of energy. Amidst a dark cosmic backdrop, the occasional brand-new light source will still arise in ours galactic remnant.

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The inspiral and merger scenario for brown dwarfs together well-separated as the systems we"ve already... <+> uncovered would take a an extremely long time as result of gravitational waves. But collisions are fairly likely. Just as red stars colliding produce blue straggler stars, brown dwarf collisions can make red dwarf stars. Over long sufficient timescales, this "blips" of irradiate may come to be the only sources illuminating the Universe.

Melvyn B. Davies, Nature 462, 991-992 (2009)

But after around 1017 years— around a million time the current age the the Universe— something starts forcing our galaxy itself to decay. The corpses flying v the galaxy, consisting of black holes, ghost stars, black dwarfs, and also rogue asteroids, comets and planets, begin gravitationally interacting with one another. Given sufficient time, 2 objects will randomly happen close through one another. When they carry out this in the internal of the galaxy, what generally happens is that one of them becomes more tightly bound to the galaxy overall, while the other one it s okay a gravitational "kick," perhaps ejecting it right into the abyss the intergalactic space. Many stellar remnants will be ejected native the galaxy in this fashion, but a little percentage (










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I am a Ph.D. Astrophysicist, author, and science communicator, who professes physics and astronomy at miscellaneous colleges. I have actually won countless awards for scientific research writing since 2008 because that my blog, Starts through A Bang, including the award for ideal science blog through the institute of Physics. My 2 books, Treknology: The scientific research of Star Trek native Tricorders to Warp Drive, past the Galaxy: exactly how humanity looked past our Milky method and discovered the entire Universe, are accessible for acquisition at Amazon. Follow me top top Twitter