Timeline of the universe

The timeline of cosmological epochs outlines the formation and subsequent evolution of the Universe from the (13.799 ± 0.021 billion years ago) to the present day. An is a moment in time from which nature or situations change to such a degree that it marks the beginning of a new ' or '.

Times on this list are measured from the moment of the Big Bang.

Planck epoch

 * c. 0 seconds (13.799 ± 0.021 ): begins: earliest meaningful time. The Big Bang occurs in which ordinary space and time develop out of a primeval state (possibly a  or ) described by a  or "". All matter and energy of the entire visible universe is contained in an unimaginably hot, dense point, a billionth the size of a nuclear particle. This state has been described as a particle . Other than a few scant details, conjecture dominates discussion about the earliest moments of the universe's history since no effective means of testing this far back in space-time is presently available. WIMPS (weakly interacting massive particles) or  and  may have appeared and been the catalyst for the expansion of the singularity. The infant universe cools as it begins expanding outward. It is almost completely smooth, with quantum variations beginning to cause slight variations in density.

Grand unification epoch

 * c. 10-43 seconds: begins: While still at an infinitesimal size, the universe cools down to 1032 .  separates and begins operating on the universe—the remaining fundamental forces stabilize into the, also known as the Grand Unified Force or  (GUT), mediated by (the hypothetical)  which allow early  at this stage to fluctuate between  and  states.

Electroweak epoch

 * c. 10-36 seconds: begins: The Universe cools down to 1028 kelvin. As a result, the  becomes distinct from the  perhaps fuelling the  of the universe. A wide array of exotic elementary particles result from decay of X and Y bosons which include  and.
 * c. 10-33 seconds: Space is subjected to, expanding by a factor of the order of 1026 over a time of the order of 10-33 to 10-32 seconds. The universe is from about 1027 down to 1022 kelvin.
 * c. 10-32 seconds: Cosmic inflation ends. The familiar s now form as a soup of hot ionized gas called ; hypothetical components of (such as s) would also have formed at this time.

Quarks epoch

 * c. 10-12 seconds: Electroweak phase transition: the four s familiar from the modern universe now operate as distinct forces. The is now a short-range force as it separates from, so matter particles can  and interact with the . The temperature is still too high for quarks to coalesce into s, and the  persists . The universe cools to 1015 kelvin.
 * c. 10-11 seconds: may have taken place with matter gaining the upper hand over anti-matter as  to  constituencies are established.

Hadron epoch

 * c. 10-6 seconds: begins: As the universe cools to about 1010 kelvin, a quark-hadron transition takes place in which quarks bind to form more complex particles—. This quark confinement includes the formation of  and , the building blocks of.

Lepton Epoch

 * c. 1 second: begins: The universe cools to 109 kelvin. At this temperature, the hadrons and antihadrons annihilate each other, leaving behind  and  – possible disappearance of . Gravity governs the expansion of the universe: neutrinos  from matter creating a.

Photon epoch

 * c. 10 seconds: begins: Most of the leptons and antileptons annihilate each other. As  and  annihilate, a small number of unmatched electrons are left over – disappearance of the positrons.
 * c. 10 seconds: Universe dominated by photons of radiation – ordinary matter particles are coupled to and radiation while dark matter particles start building non-linear structures as s. Because charged electrons and protons hinder the emission of light, the universe becomes a super-hot glowing fog.
 * c. 3 minutes: Primordial : begins as  and heavy hydrogen  and   form from protons and neutrons.
 * c. 20 minutes: Nuclear fusion ceases: normal matter consists of 75% hydrogen nuclei and 25% helium nuclei – free electrons begin scattering light.

Matter and radiation equivalence

 * c. 47,000 years (z=3600): Matter and radiation equivalence: at the beginning of this era, the expansion of the universe was decelerating at a faster rate.
 * c. 70,000 years: Matter domination in Universe: onset of gravitational collapse as the  at which the smallest structure can form begins to fall.

Cosmic Dark Age

 * c. 370,000 years (z=1,100): The "" is the period between, when the universe first becomes transparent, until the formation of the first s. : electrons combine with nuclei to form , mostly and . Distributions of hydrogen and helium at this time remains constant as the electron-baryon plasma thins. The temperature falls to 3000 kelvin. Ordinary matter particles decouple from radiation. The photons present at the time of decoupling are the same photons that we see in the  (CMB) radiation.
 * c. 400,000 years: Density waves begin imprinting characteristic signals.
 * c. 10 million years: With a trace of in the Universe, the chemistry that later  begins operating.
 * c. 10-17 million years: The "Dark Ages" span a period during which the temperature of cooled from some 4000 K down to about 60 K. The background temperature was between 373 K and 273 K, allowing the possibility of, during a period of about 7 million years, from about 10 to 17 million after the Big Bang (redshift 137–100).  (2014) speculated that  might in principle have appeared during this window, which he called "the Habitable Epoch of the Early Universe".
 * c. 100 million years: Gravitational collapse: ordinary matter particles fall into the structures created by dark matter. begins: smaller  and larger non-linear structures  begin to take shape – their  light ionizes remaining neutral gas.
 * 200–300 million years: First stars begin to shine: Because many are (some  are accounted for at this time) they are much bigger and hotter and their life-cycle is fairly short. Unlike later generations of stars, these stars are metal free. As reionization intensifies, photons of light scatter off free protons and electrons – Universe becomes opaque again.
 * 200 million years:, the "Methuselah" Star, formed, the unconfirmed oldest star observed in the Universe. Because it is a , some suggestions have been raised that second generation star formation may have begun very early on. (confirmed) – SMSS J031300.36-670839.3, forms.
 * 300 million years: First large-scale astronomical objects, protogalaxies and may have begun forming. As Population III stars continue to burn,  operates – stars burn mainly by fusing hydrogen to produce more helium in what is referred to as the . Over time these stars are forced to fuse helium to produce, ,  and other heavy elements up to  on the periodic table. These elements, when seeded into neighbouring gas clouds by , will lead to the formation of more  stars (metal poor) and.
 * 380 million years: forms, current record holder for unconfirmed oldest-known.
 * 400 million years (z=11):, the oldest-known , forms.
 * 420 million years: The quasar, the, or one of the, furthest known quasars, forms.
 * 600 million years, the oldest star found producing elements forms, marking a new point in ability to detect stars with a telescope.
 * 630 million years (z=8.2):, the oldest recorded suggests that supernovas may have happened very early on in the evolution of the Universe
 * 670 million years:, the most distant starburst or observed, forms. This suggests that  is taking place very early on in the history of the Universe as  are often associated with collisions and galaxy mergers.
 * 700 million years: Galaxies form. Smaller galaxies begin merging to form larger ones. Galaxy classes may have also begun forming at this time including, , ,  and . , the first distant quasar to be observed from the reionization phase, forms. Dwarf galaxy  forms. Galaxy or possible proto-galaxy  forms.
 * 720 million years: Possible formation of in Milky Way's . Formation of globular cluster,, in the Milky Way's galactic halo
 * 740 million years:, second-brightest globular cluster in the Milky Way, forms
 * 750 million years: Galaxy a Lyman alpha emitter galaxy, forms.  forms—galaxy is 5 times larger and 100 times more massive than the present day Milky Way illustrating the size attained by some galaxies very early on.
 * 770 million years: Quasar, one of the most distant, forms. One of the earliest galaxies to feature a suggesting that such large objects existed quite soon after the Big Bang. The large fraction of neutral hydrogen in its spectrum suggests it may also have just formed or is in the process of star formation.
 * 800 million years: Farthest extent of . Formation of : unusual population II star that is extremely metal poor consisting of mainly hydrogen and helium., one of the oldest Population II stars, forms as part of a . , the Bogwiggit Galaxy, one of the most remote galaxies, forms. Lyman alpha emitters are considered to be the progenitors of spiral galaxies like the Milky Way. , globular cluster, forms.
 * 870 million years: forms in the Milky Way. Having experienced a, the cluster has one of the highest densities among globular clusters.
 * 890 million years: Galaxy forms
 * 900 million years: Galaxy forms.
 * 910 million years: Galaxy forms

Galaxy epoch

 * 1 billion years (12.8, z=6.56): Galaxy , the most distant normal galaxy observed, forms. Formation of hyper-luminous quasar , which harbors a black hole with mass of 12 billion solar masses, one of the most massive black holes discovered so early in the universe. , a population II star, is speculated to have formed from remnants of earlier Population III stars. Visual limit of the . Reionization complete—the Universe becomes transparent again. Galaxy evolution continues as more modern looking galaxies form and develop. Because the Universe is still small in size, galaxy interactions become common place with larger and larger galaxies forming out of the process. Galaxies may have begun clustering creating the largest structures in the Universe so far - the first  and  appear.
 * 1.1 billion years (12.7 Gya): Age of the CFHQS 1641+3755.  Globular Cluster, first to have its individual stars resolved, forms in the halo of the Milky Way Galaxy. Among the clusters many stars,, a  known as the "Genesis Planet" or "Methusaleh", orbiting a  and a , the oldest observed  in Universe, forms.
 * 1.13 billion years (12.67 Gya):, globular cluster, forms
 * 1.3 billion years (12.5 Gya):, a luminous infrared galaxy, forms. , known as the Diamond Planet, forms around a pulsar.
 * 1.31 billion years (12.49 Gya): Globular Cluster forms 60,000 light-years from the galactic centre of the Milky Way
 * 1.39 billion years (12.41 Gya):, a hyper-luminous quasar, forms
 * 1.4 billion years (12.4 Gya): Age of, BPS C531082-0001, a star, among the oldest Population II stars in Milky Way. Quasar , first object observed to exceed  5, forms.
 * 1.44 billion years (12.36 Gya): globular cluster forms in Milky Way - known for large number of ""
 * 1.5 billion years (12.3 Gya):, globular cluster, forms
 * 1.8 billion years (12 Gya): Most energetic gamma ray burst lasting 23 minutes,, recorded. forms.  forms as a small dwarf galaxy on collision course with the Milky Way. Dwarf galaxy carrying the Methusaleh Star consumed by Milky Way – oldest-known star in the Universe becomes one of many population II stars of the Milky Way
 * 2.0 billion years (11.8 Gya):, the oldest observed supernova occurs – possible formed. Globular Cluster , known to have an intermediate black hole and the only globular cluster observed to include a , , forms
 * 2.02 billion years (11.78 Gya): forms – contains high number of  (89) many of which are  stars.
 * 2.2 billion years (11.6 Gya): Globular Cluster, third-brightest, forms in Milky Way
 * 2.4 billion years (11.4 Gya): Quasar forms.
 * 2.41 billion years (11.39 Gya): globular cluster forms.  forms: prototype for the  cluster, which is considered "metal-rich". That is, for a globular cluster, Messier 3 has a relatively high abundance of heavier elements.
 * 2.5 billion years (11.3 Gya):, largest globular cluster in the Milky Way forms
 * 3.0 billion years (10.8 billion Gya): Formation of the :, the first observed and , a super-earth planet, possibly the first observed , form. Gliese 581d has more potential for forming life since it is the first exoplanet of terrestrial mass proposed that orbits within the habitable zone of its parent star.
 * 3.3 billion years (10.5 Gya):, oldest observed, forms
 * 3.5 billion years (10.3 Gya): Supernova recorded
 * 3.8 billion years (10 Gya): globular cluster forms: 3 generations of stars form within the first 200 million years.
 * 4.0 billion years (9.8 Gya): Quasar forms. The  forms from a galactic merger - begins a collision course with the Milky Way., , may have formed. Beethoven Burst  recorded. Gliese 677 C, a planet in the habitable zone of its parent star, , forms
 * 4.5 billion years (9.3 Gya): Fierce star formation in Andromeda making it into a luminous galaxy
 * 5.0 billion years (8.8 Gya): Earliest, or Sunlike stars: with heavy element saturation so high, appear in which rocky substances are solidified – these nurseries lead to the formation of rocky , , , and icy
 * 5.1 billion years (8.7 Gya): Galaxy collision: spiral arms of the Milky Way form leading to major period of star formation.
 * 5.3 billion years (8.5 Gya): B, a "", first planet to be observed orbiting as part of a star system, forms.  planetary system, the flattest and most compact system yet discovered, forms – Kepler 11  considered to be a giant ocean planet with hydrogen-helium atmosphere.
 * 5.8 billion years (8 Gya): also known as Bellerophon, forms – first planet discovered orbiting a main sequence star
 * 5.9 billion years (7.9 Gya): planetary system, known as the first observed through, forms
 * 6.0 billion years (7.8 Gya): Many galaxies like become relatively stable – ellipticals result from collisions of spirals with some like  being extremely massive.
 * 6.0 billion years (7.8 Gya): The Universe continues to organize into larger wider structures. The great walls, sheets and filaments consisting of galaxy clusters and superclusters and voids crystallize. How this crystallization takes place is still conjecture. Certainly, it is possible the formation of super-structures like the may have happened much earlier, perhaps around the same time galaxies first started appearing. Either way the  becomes more modern looking.
 * 6.2 billion years (7.7 Gya):, the first gas giant observed in a single star orbit in a , forms – orbiting moons considered to have habitable properties or at the least capable of supporting water
 * 6.3 billion years (7.5 Gya, z=0.94):, farthest gamma ray burst seen with the naked eye, recorded. , metal-rich globular cluster, forms in the
 * 6.5 billion years (7.3 Gya): planetary system forms (larger than both 55 Cancri and Kepler 11 systems)
 * 6.9 billion years (6.9 Gya): Orange Giant,, forms
 * 7 billion years (6.8 Gya): North Star,, one of the significant navigable stars, forms
 * 7.64 billion years (6.16 Gya):  forms: of four planets orbiting a yellow star,  is among the first terrestrial planets to be observed from Earth
 * 7.8 billion years (6.0 Gya): Formation of Earth's near twin, orbiting its parent star
 * 7.98 billion years (5.82 Gya): Formation of or Omicron ceti, binary star system. Formation of  Star System, closest star to the Sun – formation of  closest planet to the Sun., or Gliese 1214 b, potential earth-like planet, forms
 * 8.08-8.58 billion years (5.718-5.218 Gya): star system forms
 * 8.2 billion years (5.6 Gya):, nearby yellow star forms: five planets eventually evolve from its planetary nebula, orbiting the star – Tau Ceti considered planet to have potential life since it orbits the hot inner edge of the star's habitable zone
 * 8.5 billion years (5.3 Gya):, the "Christmas Burst", considered the longest at 28 minutes, recorded

Acceleration

 * 8.8 billion years (5 Gya, z=0.5): : begins, following the  during which cosmic expansion was slowing down.
 * 8.8 billion years (5 Gya): open star cluster forms: Three exoplanets confirmed orbiting stars in the cluster including a twin of our Sun
 * 9.0 billion years (4.8 Gya):, red dwarf in , forms
 * 9.13 billion years (4.67 Gya): forms completing the Alpha Centauri trinary system

Epochs of the formation of the solar system

 * 9.2 billion years (4.6–4.57 Gya): Primal supernova, possibly triggers the formation of the.
 * 9.2318 billion years (4.5682 Gya): forms - Planetary nebula begins accretion of planets.
 * 9.23283 billion years (4.56717–4.55717 Gya): Four  evolve around the sun.
 * 9.257 billion years (4.543–4.5 Gya): Solar System of Eight planets, four terrestrial evolve around the sun.  Because of accretion many smaller planets form orbits around the proto-Sun some with conflicting orbits –  begins.  Supereon and  eon begin on the Earth.  Era begins on Mars.  Period begins on Mercury – a large planetoid strikes Mercury stripping it of outer envelope of original crust and mantle, leaving the planet's core exposed – Mercury's iron content is notably high., fifth-brightest star in our galactic neighbourhood, forms. Many of the  may have formed at this time including  and  which may presently be hospitable to some form of living organism.
 * 9.266 billion years (4.533 Gya): Formation of Earth- system following by hypothetical planetoid . Moon's gravitational pull helps stabilize Earth's fluctuating .  Period begins on Moon
 * 9.271 billion years (4.529 Gya): Major collision with a pluto-sized planetoid establishes the on Mars – formation of  of Mars
 * 9.3 billion years (4.5 Gya): Sun becomes a main sequence yellow star: formation of the and  from which a stream of  like  and  begins passing through the Solar System, sometimes colliding with planets and the Sun
 * 9.396 billion years (4.404 Gya): Liquid water may have existed on the surface of the Earth, probably due to the greenhouse warming of high levels of methane and carbon dioxide present in the atmosphere.
 * 9.4 billion years (4.4 Gya): Formation of, one of the most Earth-like planets, from a protoplanetary nebula surrounding its parent star
 * 9.5 billion years (4.3 Gya): Massive meteorite impact creates South Pole on the Moon – a huge chain of mountains located on the lunar southern limb, sometimes called "Leibnitz mountains", form
 * 9.6 billion years (4.2 Gya): widespread area of vulcanism, becomes active on Mars – based on the intensity of volcanic activity on Earth, Tharsis magmas may have produced a 1.5-bar CO2 atmosphere and a global layer of water 120 m deep increasing greenhouse gas effect in climate and adding to Martian water table. Age of the oldest samples from the
 * 9.7 billion years (4.1 Gya): Resonance in Jupiter and Saturn's orbits moves Neptune out into the Kuiper belt causing a disruption among asteroids and comets there. As a result, batters the inner Solar System.  Crater formed on, a moon of Saturn. Meteorite impact creates the  on Mars, the largest unambiguous structure on the planet.  an isolated   in the southern highlands of Mars, located at the northeastern edge of Hellas Planitia is uplifted in the wake of the meteorite impact
 * 9.8 billion years (4 Gya):, first planet detected through its transit, forms. , lenticular galaxy, disrupted by galaxy interaction: complex outer structure of shells and ripples results. Andromeda and Triangulum galaxies experience close encounter – high levels of star formation in Andromeda while Triangulum's outer disc is distorted
 * 9.861 billion years (3.938 Gya): Major period of impacts on the Moon: forms
 * 9.88 billion years (3.92 Gya): forms from large impact event: ejecta from Nectaris forms upper part of densely cratered Lunar Highlands -  Era begins on the Moon.
 * 9.9 billion years (3.9 Gya): forms on Mercury.  forms on Mercury leading to creation of "Weird Terraine" – seismic activity triggers volcanic activity globally on Mercury.  formed on Mercury. Caloris Period begins on Mercury.  forms from asteroid impact on Mars: surrounded by rugged massifs which form concentric and radial patterns around basin – several mountain ranges including  and  are uplifted in its wake
 * 9.95 billion years (3.85 Gya): Beginning of Imbrium Period on Moon. Earliest appearance of Procellarum KREEP Mg suite materials
 * 9.96 billion years (3.84 Gya): Formation of from asteroid impact on Lunar surface – collision causes ripples in crust, resulting in three concentric circular features known as  and
 * 10 billion years (3.8 Gya): In the wake of Late Heavy Bombardment impacts on the Moon, large molten depressions dominate lunar surface – major period of Lunar vulcanism begins (to 3 Gyr).  eon begins on the Earth.
 * 10.2 billion years (3.6 Gya): forms on Mars, largest volcano in terms of area
 * 10.4 billion years (3.5 Gya): Earliest fossil traces of life on Earth (s)
 * 10.6 billion years (3.2 Gya): begins on Mars: Martian climate thins to its present density: groundwater stored in upper crust (megaregolith) begins to freeze, forming thick cryosphere overlying deeper zone of liquid water – dry ices composed of frozen carbon dioxide form  period begins on the Moon: main geologic force on the Moon becomes impact cratering
 * 10.8 billion years (3 Gya): forms on Mercury – unlike many basins of similar size on the Moon, Beethoven is not multi ringed and ejecta buries crater rim and is barely visible
 * 11.2 billion years (2.5 Gya): begins
 * 11.6 billion years (2.2 Gya): Last great tectonic period in Martian geologic history:, largest canyon complex in the Solar System, forms – although some suggestions of thermokarst activity or even water erosion, it is suggested Valles Marineris is rift fault

Recent history

 * 11.8 billion years (2 Gya): Star formation in slows. Formation of  from a galaxy collision.  largest volcano in the Solar System forms
 * 12.1 billion years (1.7 Gya): captured into an orbit around Milky Way Galaxy
 * 12.7 billion years (1.1 Gya): Period begins on Moon: defined by impact craters that possess bright optically immature ray systems
 * 12.8 billion years (1 Gya): Kuiperian Era (1 Gyr – present) begins on Mercury: modern Mercury, desolate cold planet influenced by space erosion and solar wind extremes. Interactions between Andromeda and its companion galaxies Messier 32 and Messier 110. Galaxy collision with Messier 82 forms its spiral patterned disc: galaxy interactions between NGC 3077 and Messier 81
 * 13 billion years (800 ): forms from impact on Lunar surface in the area of Oceanus Procellarum – has terrace inner wall and 30 km wide, sloping rampart that descends nearly a kilometer to the surrounding mare
 * 13.175 billion years (625 Mya): formation of star cluster: consists of a roughly spherical group of hundreds of stars sharing same age, place of origin, chemical content and motion through space
 * 13.2 billion years (600 Mya): Collision of spiral galaxies leads to creation of . Whirlpool Galaxy collides with forming present connected galaxy system.  forms around parent star : first planet to reveal climate, organic constituencies, even colour (blue) of its atmosphere
 * 13.6–13.5 billion years (300-200 Mya):, the brightest star in the Earth's sky, forms.
 * 13.795 billion years (100 Mya): Formation of  Star Cluster
 * 13.790 billion years (20 Mya): Possible formation of
 * 13.788 billion years (12 Mya): forms.
 * 13.792 billion years (7.6 Mya): forms.
 * 13.795 billion years (4.4 Mya):, first directly imaged exoplanet, forms
 * 13.8 billion years (Without uncertainties): Present day.