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The observable universe contains as many as an estimated 2 trillion galaxies [95] [96] [97] and, overall, as many as an estimated 10 24 stars [98] [99] – more stars (and earth-like planets) than all the grains of beach sand on planet Earth; [100] [101] [102] but less than the total number of atoms estimated in the universe as 10 82; [103] and ...
Prototype Galaxies Class Galaxy Constellation Date Notes BL Lac object: BL Lacertae (BL Lac) Lacerta: This AGN was originally catalogued as a variable star, and "stars" of its type are considered BL Lac objects. Hoag-type Galaxy Hoag's Object: Serpens Caput: This is the prototype Hoag-type ring galaxy: Giant LSB galaxy: Malin 1: Coma Berenices ...
The Milky Way is an example of a spiral galaxy. It is estimated that there are between 200 billion [7] (2 × 10 11) to 2 trillion [8] galaxies in the observable universe. Most galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years) and
List of the largest known stars in Andromeda and Triangulum galaxies Star name Solar radii (Sun = 1) Galaxy Method [a] Notes Theoretical limit of star size (Andromeda Galaxy) ≳1,750 [11] L/T eff: Estimated by measuring the fraction of red supergiants at higher luminosities in a large sample of stars. Assumes an effective temperature of 3,625 K.
Cosmic inflation expands space by a factor of the order of 10 26 over a time of the order of 10 −36 to 10 −32 seconds. The universe is supercooled from about 10 27 down to 10 22 Kelvins. [18] The strong interaction becomes distinct from the electroweak interaction. Electroweak epoch ends 10 −12 s 10 15 K (150 GeV)
Common targets of amateur astronomers include the Sun, the Moon, planets, stars, comets, meteor showers, and a variety of deep-sky objects such as star clusters, galaxies, and nebulae. Astronomy clubs are located throughout the world and many have programs to help their members set up and complete observational programs including those to ...
The Hubble eXtreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed at that time. Except for the few stars in the foreground (which are bright and easily recognizable because only they have diffraction spikes), every speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is ...
Intergalactic space takes up most of the volume of the universe, but even galaxies and star systems consist almost entirely of empty space. Most of the remaining mass-energy in the observable universe is made up of an unknown form, dubbed dark matter and dark energy .