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The Milky Way [c] is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
The Solar System's location in the Milky Way is a factor in the evolutionary history of life on Earth. Spiral arms are home to a far larger concentration of supernovae , gravitational instabilities, and radiation that could disrupt the Solar System, but since Earth stays in the Local Spur and therefore does not pass frequently through spiral ...
Location of the Solar System within the Milky Way. The Solar System travels alone through the Milky Way in a circular orbit approximately 30,000 light years from the Galactic Center. Its speed is about 220 km/s. The period required for the Solar System to complete one revolution around the Galactic Center, the galactic year, is in the range of ...
Frank Drake. The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.. The equation was formulated in 1961 by Frank Drake, not for purposes of quantifying the number of civilizations, but as a way to stimulate scientific dialogue at the first scientific meeting on the search for extraterrestrial ...
Bottom: Logarithmic scale of the Solar System and Voyager 1 's position.. The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium.
A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, because gases or other material may be falling from the inner edge of the disk onto the surface of the star.
The most widely accepted model of planetary formation is known as the nebular hypothesis. This model posits that, 4.6 billion years ago, the Solar System was formed by the gravitational collapse of a giant molecular cloud spanning several light-years. Many stars, including the Sun, were formed within this collapsing cloud.
For millennia, what today is known to be the Solar System was regarded as the "whole universe", so the knowledge of both mostly advanced in parallel. A clear distinction was not made until around the mid-17th century. Since then, incremental knowledge has been gained not only about the Solar System, but also about outer space and its deep-sky ...