13.799-4.57 billion years ago (Before the Solar System Era)
13.799 billion years ago - Our Universe was born.
13.799 billion years ago - Planck epoch begins: Big Bang occurs in which ordinary space and time develop out of a primeval state described by a quantum theory of gravity or "Theory of everything". All matter and energy of the universe is contained in a hot, dense point (gravitational singularity)
13.799-(3.1689e-60) billion years ago - Gravity separates and begins operating on the universe—the remaining fundamental forces stabilize into the electronuclear force, also known as the Grand Unified Force or Grand Unified Theory (GUT), mediated by (the hypothetical) X and Y bosons which allow early matter at this stage to fluctuate between baryon and lepton states.
13.799-(3.1689e-52) billion years ago - inflation, expands the universe by a factor of the order of 10^26 over a time of the order of 10^−33 to 10^−32 seconds. The universe is supercooled from about 10^27 down to 10^22 kelvin.
13.799-(3.1689e-49) billion years ago - Cosmic inflation ends. The familiar elementary particles now form as a soup of hot ionized gas called quark–gluon plasma;
13.799-(3.1689e-29) billion years ago - Electroweak phase transition: The weak nuclear force is now a short-range force as it separates from electromagnetic force, so matter particles can acquire mass and interact with the Higgs Field. The quark–gluon plasma persists (Quark epoch). The universe cools to 1015 kelvin.
13.799-(3.1689e-23) billion years ago - As the universe cools to about 10 billion kelvin, a quark-hadron transition takes place in which quarks become confined in more complex particles—hadrons.
13.799-(3.1689e-17) billion years ago - Lepton epoch begins: The universe cools to 1 billion kelvin. At this temperature, the hadrons and antihadrons annihilate each other, leaving behind leptons and antileptons – possible disappearance of antiquarks. Gravity governs the expansion of the universe: neutrinos decouple from matter creating a cosmic neutrino background.
13.799-(3.1689e-16) billion years ago - Photon epoch begins: Most leptons and antileptons annihilate each other. As electrons and positrons annihilate, a small number of unmatched electrons are left over – disappearance of the positrons. Universe dominated by photons of radiation – ordinary matter particles are coupled to light and radiation.
13.799-(5.704e-15) billion years ago - Primordial nucleosynthesis: nuclear fusion begins as lithium and heavy hydrogen (deuterium) and helium nuclei form from protons and neutrons.
13.799-(3.8027e-14) billion years ago - Primordial nucleosynthesis ceases
13.798953 billion years ago - (z = 3600): Matter and radiation equivalence
13.79893 billion years ago - As the temperature falls, gravity overcomes pressure allowing first aggregates of matter to form.
13.79863 billion years ago - (z = 1,100): The "Dark Ages" is the period between decoupling, when the universe first becomes transparent, until the formation of the first stars. Recombination: electrons combine with nuclei to form atoms, mostly hydrogen and helium. Ordinary matter particles decouple from radiation. The photons present during the decoupling are the same photons seen in the cosmic microwave background (CMB) radiation.
13.789 billion years ago - The "Dark Ages" span a period during which the temperature of cosmic microwave background radiation cooled from some 4,000 K (3,730 °C; 6,740 °F) down to about 60 K (−213.2 °C; −351.7 °F).
13.699 billion years ago - Gravitational collapse: ordinary matter particles fall into the structures created by dark matter. Reionization begins: smaller (stars) and larger non-linear structures (quasars) begin to take shape – their ultraviolet light ionizes remaining neutral gas.
13.61 billion years ago - Milky Way Galaxy was formed.
13.599 billion years ago - First stars begin to shine: Because many are Population III stars (some Population II stars 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. Reionization begins, with the absorption of certain wavelengths of light by neutral hydrogen creating Gunn–Peterson troughs. The resulting ionized gas (especially free electrons) in the intergalactic medium causes some scattering of light, but with much lower opacity than before recombination due the expansion of the universe and clumping of gas into galaxies.
13.599 billion years ago - The oldest-known star (confirmed) – SMSS J031300.36−670839.3, forms.
13.51 billion years ago - Pinwheel Galaxy was formed.
13.5 billion years ago - First Black Hole was formed.
13.499 billion years ago - First large-scale astronomical objects, protogalaxies and quasars may have begun forming. As Population III stars continue to burn, stellar nucleosynthesis operates – stars burn mainly by fusing hydrogen to produce more helium in what is referred to as the main sequence. Over time these stars are forced to fuse helium to produce carbon, oxygen, silicon and other heavy elements up to iron on the periodic table. These elements, when seeded into neighbouring gas clouds by supernova, will lead to the formation of more Population II stars (metal poor) and gas giants.
13.479 billion years ago - (z = 13.3): HD1, the oldest-known spectroscopically-confirmed galaxy, forms.
13.419 billion years ago - UDFj-39546284 forms, current record holder for unconfirmed oldest-known quasar.
13.4 billion years ago - GN-z11 was formed.
13.3 billion years ago - MACS1149-JD1 was formed.
13.292 billion years ago - The Last Quasi Star.
13.28 billion years ago - Black Eye Galaxy was formed.
13.25 billion years ago - Sombrero Galaxy was formed.
13.199 billion years ago - HE 1523-0901, the oldest star found producing neutron capture elements forms, marking a new point in ability to detect stars with a telescope.
13.169 billion years ago - GRB 090423, the oldest gamma-ray burst recorded suggests that supernovas may have happened very early on in the evolution of the Universe
13.1 billion years ago - represents a distant point in cosmic history, roughly equivalent to observing a galaxy at a redshift of 8.55
13 billion years ago - first stars in the central bar portion of the Milky Way are born,
13 billion years ago - Magellanic Clouds were formed.
12.9 billion years ago - Earendel Star was formed.
12.9 billion years ago - Reionization era ends.
12.75 billion years ago - Hoag's Object was formed.
12.7 billion years ago - Mu Cassiopeiae was formed.
12.4 billion years ago - BRI 1335-0417 was formed.
12.3 billion years ago - Methuselah Star was formed.
12.1 billion years ago - Wolfe Disk was formed.
11.7 billion years ago - ceers-2112 was formed.
11.6 billion years ago - galaxies were still actively forming and evolving, including the formation of star nurseries and the observation of early supernovas
11.5 billion years ago - marks a significant period in the early universe, specifically referencing a supernova explosion observed by the Hubble Space Telescope and also a period when the Milky Way galaxy was interacting with a smaller galaxy, Gaia-Enceladus
11.5 billion years ago - Kapteyn's Star was formed.
11.4 billion years ago - AT 2023adsv, erupted
11.2 billion years ago - Kepler-444 was formed.
11 billion years ago - first stars in the thick disk region of the Milky Way are formed.
11 billion years ago - Universe starts to cool (13000 K)
11 billion years ago - Star formation rate peaks
10.7 billion years ago - BX442 was formed.
10.5 billion years ago - DES16C2nm is a supernova that exploded, making it the most distant ever detected..
10.4 billion years ago - Universe becomes habitable.
10.2 billion years ago - Rho Coronae Borealis was formed.
10.01 billion years ago - Andromeda Galaxy was formed.
10 billion years ago - Barnard's Star was formed.
10 billion years ago - Gaia Enceladus merges into Milky Way.
9.9 billion years ago - JKCS 041 was formed
9.8 billion years ago - the universe entered the dark-energy-dominated era. This era is marked by the acceleration of the universe's expansion, which is caused by a mysterious form of energy called dark energy.
9.6 billion years ago - Milky Way star formation rate stabilizes
9 billion years ago - Oldest known evidence for dark energy
9.3 billion years ago - 15 Leonis Minoris was formed.
9.1652 billion years ago - R Doradus was formed.
8.9443 billion years ago - Tau Ceti was formed.
8.8 billion years ago - Milky Way's thin disk starts to form.
8.6 billion years ago - 55 Cancri was formed.
8.5 billion years ago - first stars in the thin disk region of the Milky Way are formed.
8.5 billion years ago - HD 34445 was formed.
8.4 billion years ago - a time in the early universe, specifically 5.3 billion years after the Big Bang, when the universe was still young and turbulent.
8.2 billion years ago - the universe was already a significant portion of its current age, with galaxies, stars, and possibly early life forms already in place. This period occurred roughly halfway between the Big Bang and the present day.
8.047 billion years ago - Lalande 21185 was formed.
8 billion years ago - Teegarden's Star was formed.
8 billion years ago - Luyten's Star was formed.
8 billion years ago - Milky Way star formation rate begins to decline.
7.6 billion years ago - TRAPPIST-1 was formed.
7.6 billion years ago - Kepler-37 was formed.
7.5 billion years ago - GRB 080319B, Most powerful gamma ray burst ever.
7.4 billion years ago - GRB 070714B, a short gamma-ray burst has occured.
7.1 billion years ago - Arcturus was formed.
7.1 billion years ago - Universe cools below 5 K.
7 billion years ago - Gliese 12 was formed.
6.9 billion years ago - 40 Eridani A was formed.
6.81 billion years ago - 64 Piscium was formed.
6.5 billion years ago - Milky Way starts spiralizing.
6.4 billion years ago - Aldebaran was formed as a white star.
6.3452 billion years ago - 61 Virginis was formed.
6.32 billion years ago - 81 Geminorum was formed.
6.194 billion years ago - Delta Eridani was formed.
6.1 billion years ago - 61 Cygni was formed.
6 billion years ago - Dark energy overtakes gravity: Universe's expansion rate starts to accelerate.
6 billion years ago - Mira was formed.
5.7 billion years ago - Gamma Cephei was formed.
5.5 billion years ago - Milky Way becomes a spiral galaxy.
5.49 billion years ago - 37 Geminorum was formed.
5.4772 billion years ago - Scholz's Star was formed as the dimmest red dwarf.
5.4 billion years ago - Eta Cassiopeiae was formed.
5.3 billion years ago - Alpha Centauri A and B were formed.
5.1 billion years ago - the formation of the spiral arms of the Milky Way and the beginning of the dark-energy dominated era began to occur.
5 billion years ago - z = 0.5 Acceleration: dark-energy dominated era begins, following the matter-dominated era during which cosmic expansion was slowing down.
4.9132 billion years ago - Chara Star was formed.
4.85 billion years ago - Proxima Centauri was formed.
4.8 billion years ago - 51 Pegasi was formed.
4.7 billion years ago - SN 2005ap supernova occurs.
4.65 billion years ago - 2 Neutron Stars merged, cause the formation of Solar System 80 million years later.
4.6 billion years ago - Nu2 Canis Majoris was formed.
