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Its two component stars orbit every 76 days at a separation of about 1 astronomical unit (AU). [11] HR 4729, also known as Acrux C, is a more distant companion, forming a triple star through small telescopes. C is also a spectroscopic binary, which brings the total number of stars in the system to at least five.
R ∗ = 1 yr −1 (1 star formed per year, on the average over the life of the galaxy; this was regarded as conservative) f p = 0.2 to 0.5 (one fifth to one half of all stars formed will have planets) n e = 1 to 5 (stars with planets will have between 1 and 5 planets capable of developing life) f l = 1 (100% of these planets will develop life)
This article documents the most distant astronomical objects discovered and verified so far, and the time periods in which they were so classified. For comparisons with the light travel distance of the astronomical objects listed below, the age of the universe since the Big Bang is currently estimated as 13.787±0.020 Gyr.
This illustrates the fact that there are far more faint stars than bright stars: in the entire sky, there are about 500 stars brighter than apparent magnitude 4 but 15.5 million stars brighter than apparent magnitude 14. [108] The apex of the Sun's way, or the solar apex, is the direction that the Sun travels through space in the Milky Way.
Such an event could theoretically accelerate a star to such high speeds that it becomes a hypervelocity star, thereby escaping the gravitational well of the entire galaxy. [5] In this respect, model calculations (from 1988) predict the supermassive black hole in the center of our Milky Way galaxy to expel one star every 100,000 years on average ...
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution
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A parsec is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond (not to scale). The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles).