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By comparison, the total mass of all the stars in the Milky Way is estimated to be between 4.6 × 10 10 M ☉ and 6.43 × 10 10 M ☉.
The first aspect of the Fermi paradox is a function of the scale or the large numbers involved: there are an estimated 200–400 billion stars in the Milky Way (2–4 × 10 11) and 70 sextillion (7×10 22) in the observable universe.
By 1781 the final published list grows to 103 objects, 34 of which turn out to be galaxies. 1785 — William Herschel carried the first attempt to describe the shape of the Milky Way and the position of the Sun in it by carefully counting the number of stars in different regions of the sky.
Galaxies are categorized according to their visual morphology as elliptical, [5] spiral, or irregular. [6] The Milky Way is an example of a spiral galaxy. It is estimated that there are between 200 billion [7] ( 2 × 1011) to 2 trillion [8] galaxies in the observable universe.
Age: Stars are usually grouped into Population I (young) and Population II (old). Location: In the Milky Way galaxy the groups are described as thin disk, thick disk, central bulge, and halo. Multiplicity: Most stars are members of double star, or triple star, or even double-double star systems.
In November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy. 11 billion of these estimated planets may be orbiting sun-like stars.
The observable universe contains as many as an estimated 2 trillion galaxies and, overall, as many as an estimated 10 24 stars – more stars (and earth-like planets) than all the grains of beach sand on planet Earth.
Ceers-2112 formed soon after the big bang created the universe (which is estimated to be 13.8 billion years old), and the galaxy’s distinct structure was already in place 2.1 billion years later.
In November 2013, it was estimated that 22±8% of Sun-like stars in the Milky Way galaxy may have an Earth-sized planet in the habitable zone. Assuming 200 billion stars in the Milky Way, that would be 11 billion potentially habitable Earths, rising to 40 billion if red dwarfs are included.
Based upon the emerging science of nucleocosmochronology, the Galactic thin disk of the Milky Way is estimated to have been formed 8.8 ± 1.7 billion years ago. It may have collided with a smaller satellite galaxy, causing the stars in the thin disk to be shaken up and creating the thick disk, [7] while the gas would have settled into the ...
