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The idea is that since all the stars share a common space velocity, they will appear to move towards a point of common convergence ("vanishing point") on the sky. This is essentially a perspective effect. Using the moving-cluster method, the distance to a given star cluster (in parsecs) can be determined using the following equation:
Stars slowly lose mass by the emission of a stellar wind from the photosphere. The star's magnetic field exerts a torque on the ejected matter, resulting in a steady transfer of angular momentum away from the star. Stars with a rate of rotation greater than 15 km/s also exhibit more rapid mass loss, and consequently a faster rate of rotation decay.
For most stars seen in the sky, the observed proper motions are small and unremarkable. Such stars are often either faint or are significantly distant, have changes of below 0.01″ per year, and do not appear to move appreciably over many millennia. A few do have significant motions, and are usually called high-proper motion stars.
The internal structure of a main sequence star depends upon the mass of the star. In stars with masses of 0.3–1.5 solar masses (M ☉), including the Sun, hydrogen-to-helium fusion occurs primarily via proton–proton chains, which do not establish a steep temperature gradient. Thus, radiation dominates in the inner portion of solar mass stars.
Regulus is the brightest star in the constellation of Leo (right tip, below is bright Jupiter in 2004). Regulus is a multiple star system consisting of at least four stars and a substellar object . Regulus A is the dominant star, with a binary companion 177" distant that is thought to be physically related.
Below there are lists the nearest stars separated by spectral type. The scope of the list is still restricted to the main sequence spectral types: M , K , F , G , A , B and O . It may be later expanded to other types, such as S , D or C .
This number is likely much higher, due to the sheer number of stars needed to be surveyed; a star approaching the Solar System 10 million years ago, moving at a typical Sun-relative 20–200 kilometers per second, would be 600–6,000 light-years from the Sun at present day, with millions of stars closer to the Sun.
Nevertheless, very hot main-sequence stars are still sometimes called dwarfs, even though they have roughly the same size and brightness as the "giant" stars of that temperature. [21] The common use of "dwarf" to mean the main sequence is confusing in another way because there are dwarf stars that are not main-sequence stars.