The corresponding mass-loss rates approach and sometimes exceed one hundred-thousandth of a solar mass per year, which means that one entire solar mass (perhaps a tenth of the total mass of the star) is carried away into space in a relatively short span of 100,000 years. Observations of their ultraviolet spectra with telescopes on sounding rockets and spacecraft have shown that their wind speeds often reach 3,000 km (roughly 2,000 miles) per second, while losing mass at rates up to a billion times that of the solar wind. The highly luminous hot, blue stars have by far the strongest stellar winds. Get a Britannica Premium subscription and gain access to exclusive content. Also among the brightest stars are Rigel A, a young supergiant in the constellation Orion, and Canopus, a bright beacon in the Southern Hemisphere often used for spacecraft navigation. Sirius B is a prime example, having a radius one-thousandth that of the Sun, which is comparable to the size of Earth. Several of the stellar class of white dwarf stars, which have low luminosities and high densities, also are among the brightest stars. The latter has a radius some 300 times that of the Sun, whereas the variable star Betelgeuse oscillates between roughly 300 and 600 solar radii. Betelgeuse and Antares A are examples of supergiant stars. Observations with an interferometer (an instrument that measures the angle subtended by the diameter of a star at the observer’s position), combined with parallax measurements (which yield a star’s distance see below Determining stellar distances), give sizes of 12 and 22 solar radii for Arcturus and Aldebaran A. Aldebaran A, Arcturus, and Capella A are examples of giant stars, whose dimensions are much larger than those of the Sun. Sirius A and Vega, though much brighter, also are dwarf stars their higher temperatures yield a larger rate of emission per unit area. Stars such as Altair, Alpha Centauri A and B, and Procyon A are called dwarf stars their dimensions are roughly comparable to those of the Sun. Many stars vary in the amount of light they radiate. Learn about the different types of stars categorized according to their mass and temperature - red dwarfs, red giants, supergiants, white, and brown dwarf stars See all videos for this article General considerations The Sun as a point of comparison Variations in stellar size The myriad other stars are compared with the Sun, strongly implying that “our” star is in no way special. Included in the discussion are the sizes, energetics, temperatures, masses, and chemical compositions of stars, as well as their distances and motions. This article describes the properties and evolution of individual stars. Somewhat related to star clusters are stellar associations, which consist of loose groups of physically similar stars that have insufficient mass as a group to remain together as an organization. The members of such stellar groups are physically related through common origin and are bound by mutual gravitational attraction. Many stars occur in pairs, multiple systems, or star clusters. Of the tens of billions of trillions of stars composing the observable universe, only a very small percentage are visible to the naked eye. Star, any massive self-luminous celestial body of gas that shines by radiation derived from its internal energy sources. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.This Time in History In these videos, find out what happened this month (or any month!) in history. #WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.
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