The name Milkyway is very old and descend properly from the Greec word "Galaxias Kyklos" which means "The Sircle of Milk". The romanian has meanwhile changed this name to "Via Lactea" which means The Milkyway. The Milkyway is a spiral galaxy with a diameter corresponding about 100 000 lightyears. The assembling visible mass contains about 200 billion Sunmasses. The Milkyway belongs to a local group with 30 galaxies, which are placed in our "neighbourhood".
In the middle of the Milkyway system is an area with particurlarly high density of stars. This globular centre has a diameter on about 30 000 ly (lightyears). The spiralarms from the kernel forms the disk (look at the image below). The radius from the kernel is about 40 000 - 50 000 lightyears, but the thickness is only 3000 ly.
Image: The Sunsystem is placed in the outer part of the Milkyway, in the part that calls the Orion Arm..
The most star-deliveries (birth) happens in the disk, about 12 000 ly. from the kernel and out to the suns course. The stars in the globular kernel is in general much older than the stars in the disc. In the centre of the Milkyway system is something strange like a Black Hole, with several millions sunmasses. Black Hole`s are according to the astrophysic one of the Universe`s most destructive strength. Its almost like an evil power that swallow everything in the nearness.
Its a common agreement among the cosmologes that the Milkyway from outward, looks like the Andromeda galaxy M31 (our closest neighbourgalaxy) - 2.5 mill. lightyears away from the Sun. The Milkyway system is surrounded by a ball-shaped "halo", which is about 40 000 l.y. in diameter. In this area we can find more than 90 % of the Milkyway`s mass, called Dark matter.
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