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Definition: galaxy from Collins English Dictionary

n pl -axies

1 any of a vast number of star systems held together by gravitational attraction in an asymmetric shape (an irregular galaxy) or, more usually, in a symmetrical shape (a regular galaxy), which is either a spiral or an ellipse Former names: island universe, extragalactic nebula Related adjective: galactic

2 a splendid gathering, esp one of famous or distinguished people

[C14 (in the sense: the Milky Way), from Medieval Latin galaxia, from Latin galaxias, from Greek, from gala milk; related to Latin lac milk]

galaxy

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Grouping of millions or billions of stars, held together by gravity. There are billions of galaxies in the universe . There are different types, including spiral, barred spiral, and elliptical galaxies. Our own Galaxy, the Milky Way , is about 100,000 light years across (a light year is the distance light travels in a year, about 9.5 trillion km/6 trillion mi; 1 trillion = 10 12 ), and contains at least 100 billion stars. The galaxies are moving away from our own in all directions. The universe is thus expanding in all directions. The evidence for this comes from examining light from the galaxies by splitting the light into a spectrum. A feature known as the red shift appears, in which the light is shifted towards the red end of the spectrum due to an increase in wavelength caused by the galaxies' recession. Spiral galaxies , such as the Milky Way, are flattened in shape, with a central bulge of old stars surrounded by a disc of younger stars, arranged in spiral arms like a Catherine…
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Full text Article galaxy

From Astronomy Encyclopedia
galaxy A general outline for the structure of a...
Huge, gravitationally bound, assemblage of stars, gas, dusta and DARK MATTER , an example of which is our own GALAXY . Such objects span a wide range of size, luminosity and mass, with the largest CD GALAXIES being a million times brighter than the faintest known DWARF GALAXIES . The forms of most…
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Full text Article galaxy

From Philip's Encyclopedia
Huge assembly of stars , dust and gas. There are three main types, as classified by Edwin Hubble in 1925. Elliptical galaxies (E) are round or elliptical systems, showing a gradual decrease in brightness from the centre outwards. Spiral galaxies (S) are flattened, disc-shaped systems in which young…
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Full text Article galaxy

From The Columbia Encyclopedia
large aggregation of stars , gas, dust, and usually dark matter , typically containing billions of stars. Recognition that galaxies are independent star systems outside the Milky Way came from a study of the Andromeda Galaxy (1926–29) by Edwin P. Hubble that indicated the great distances at which…
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Full text Article GALAXY

From Gaither's Dictionary of Scientific Quotations
American astronomer …not all galaxies fit the schematic idealization of the Hubble sequence of nebular forms. In fact, when looked at closely enough, every galaxy is peculiar. Appreciation of these peculiarities is important in order to build a realistic picture of what galaxies are really like. …
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Description Time Total Time A galaxy is a collection of several billion stars and interstellar matter isolated in space. 00:01 – 00:10 00:01:57 Galaxies can be very different in terms of shape. According to the classifications established by the astronomer Edwin Hubble in the 1920s, galaxies have…
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Full text Article galaxy

From The Penguin Dictionary of Science
galaxy The conventional classification of...
A vast assemblage of ➤ stars , interstellar matter (➤ interstellar medium ) and ➤ dark matter . The galaxy in which the Sun is located is named ‘the Galaxy’, with a capital ‘G’. It is a large ➤ spiral galaxy over 100 000 light years in diameter, containing about 10 11 stars. From our vantage point…
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Full text Article galaxy

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Grouping of millions or billions of stars, held together by gravity. There are billions of galaxies in the universe . There are different types, including spiral, barred spiral, and elliptical galaxies. Our own Galaxy, the Milky Way , is about 100,000 light years across (a light year is the distance…
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Full text Article galaxies

From Collins Dictionary of Astronomy
Giant assemblies of stars, gas, and dust into which most of the visible matter in the Universe is concentrated. Each galaxy exists as a separate, though not always entirely independent, system held together and organized largely by the gravitational interactions between its various components. When…
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Full text Article GALAXIES

From National Geographic Answer Book: 10,001 Fast Facts About Our World Full text Article THE UNIVERSE
MILKY WAY FACTS TYPE OF GALAXY Spiral TOTAL MASS 1-3 trillion solar masses including dark matter (1 solar mass = 1.99 x 10 30 kg) DISK DIAMETER 100,000 light-years NUMBER OF STARS 100-400 billion AGE OF OLDEST STAR CLUSTERS 13.5 billion years DISTANCE OF NUCLEUS FROM SUN 26,000 light-years The…
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Full text Article galaxies

From Science Encyclopedia: Encyclopedia of Space and Astronomy
The center of the Andromeda Galaxy (M31) as...
A galaxy is a very large accumulation of from 10 6 to 10 12 stars. Galaxies—or “island universes,” as they are sometimes called—come in a variety of shapes and sizes. They range from dwarf galaxies, such as the Magellanic Clouds, to giant spiral galaxies, such as the Andromeda Galaxy. Astronomers…
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