What galaxies are
Have you been invited to an astronomical dinner, and you don’t want to come hempty-handed? Here we have the perfect recipe for you!
Let’s take at least 100 billions of stars and all the interstellar gas as much as you like. Then add enough interstellar dust and dark matter. Cook your mixture at least at 1032 K and do not forget the fundamental ingredient: the gravity! Let’s make all cold for a billion of years and… voilà! You will have a new galaxy, ready to be waited on!
It seems easy to create a new galaxy, but really we did not know what a galaxy was, until a very few time ago. In the past, we didn’t have powerful observation instruments as today, so galaxies seemed small regions, placed everywhere in the skies and featured by a bright vagueness, called, exactly, nebulas.
Until the Twenties of the last century, scientists supposed that these nebulas were parts of our galaxy, whose real dimensions were still misterious. In 1924, astronomer Edwin Hubble, thanks to one of the most powerful telescope of his time, had been able to see some regions of the nebula of Andromeda, confirming that it was a single galaxy, external to ours. Already around 1929, Hubble discovered 18 galaxies, each one containing billions of stars. But are all these galaxies equal?
Special reports
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28 January 2014
Gaia satellite scanning the sky
On December 19, 2013 the new satellite Gaia lifted off from the launching pad...
14 May 2014
Another Earth in the Universe
NASA’s Kepler Telescope, has discovered the first Earth-sized extrasolar planet...
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31 March 2014
A day on board the International Space Station
How astronauts spend their time in space?
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6 March 2014
A beam of antimatter could help to unravel the secrets of the Universe
At the end of January 2014 it was announced that at the CERN...
13 September 2013
The phenomenon of gravitational lenses
If we look carefully at the image taken with the Hubble Space Telescope...
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28 January 2014
Gaia satellite scanning the sky
On December 19, 2013 the new satellite Gaia lifted off from the launching pad...
-
14 May 2014
Another Earth in the Universe
NASA’s Kepler Telescope, has discovered the first Earth-sized extrasolar planet...
31 March 2014
A day on board the International Space Station
How astronauts spend their time in space?
-
28 January 2014
Gaia satellite scanning the sky
On December 19, 2013 the new satellite Gaia lifted off from the launching pad...
-
14 May 2014
Another Earth in the Universe
NASA’s Kepler Telescope, has discovered the first Earth-sized extrasolar planet...
From the Multimedia section
Facts
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The comet’s tail
Comets are “dirty snowballs” that spend most of their life at the edges of the Solar System...
The definition of a dwarf planet
Astronomy, like all scientific disciplines, is continuously evolving...
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The cosmic microwave background radiation
In 1965, while studying the ground noise of a radio antenna...
Cosmic collision
When two galaxies start to approach, the tidal attraction forces deform their structures...
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The comet’s tail
Comets are “dirty snowballs” that spend most of their life at the edges of the Solar System...
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The definition of a dwarf planet
Astronomy, like all scientific disciplines, is continuously evolving...
-
The comet’s tail
Comets are “dirty snowballs” that spend most of their life at the edges of the Solar System...
-
The definition of a dwarf planet
Astronomy, like all scientific disciplines, is continuously evolving...