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The Hubble constant is most frequently quoted in km/s/Mpc, which gives the speed of a galaxy 1 megaparsec (3.09 × 10 19 km) away as 70 km/s. Simplifying the units of the generalized form reveals that H 0 specifies a frequency (SI unit: s −1), leading the reciprocal of H 0 to be known as the Hubble time (14.4 billion years). The Hubble ...
Comparison of the night sky with the night sky of a hypothetical planet within the Milky Way 10 billion years ago, at an age of about 3.6 billion years and 5 billion years before the Sun formed. [261] Globular clusters are among the oldest objects in the Milky Way, which thus set a lower limit on the age of the Milky Way.
2020 – After a 20-year-long survey, astrophysicists of the Sloan Digital Sky Survey publish the largest, most detailed 3D map of the universe so far, fill a gap of 11 billion years in its expansion history, and provide data which supports the theory of a flat geometry of the universe and confirms that different regions seem to be expanding at ...
The estimated time for all nucleons in the observable universe to decay, if the hypothesized proton half-life takes its smallest possible value (8.2 × 10 33 years). [151] [note 4] 10 36 –10 38 (1–100 undecillion) The estimated time for all remaining planets and stellar-mass objects, including the Sun, to disintegrate if proton decay can ...
The universe has appeared much the same as it does now, for many billions of years. It will continue to look similar for many more billions of years into the future. The galactic disk of the Milky Way is estimated to have been formed 8.8 ± 1.7 billion years ago but only the age of the Sun, 4.567 billion years, is known precisely. [69]
One galactic year is approximately 225 million Earth years. [2] The Solar System is traveling at an average speed of 230 km/s (828,000 km/h) or 143 mi/s (514,000 mph) within its trajectory around the Galactic Center, [ 3 ] a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to ...
The highest-redshift quasar known (as of August 2024) is UHZ1, with a redshift of approximately 10.1, [48] which corresponds to a comoving distance of approximately 31.7 billion light-years from Earth (these distances are much larger than the distance light could travel in the universe's 13.8-billion-year history because the universe is expanding).
While estimates of the redshifts of HDF galaxies are somewhat crude, astronomers believe that star formation was occurring at its maximum rate 8–10 billion years ago, and has decreased by a factor of about 10 since then. [19] Another important result from the HDF was the very small number of foreground stars present.