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Universe Colour
The average colour of the universe is actually "cosmic latte", 'latteo' means 'Milky Way' in Galileo's native Italian". While the Universe is now kind of beige, it was much bluer in the distant past, at a time when it was only 2,500 million years old.The Cosmic Spectrum which represents all the sum of all the energy in the local volume of the universe emitted at different optical wavelengths of light.
For all that we think we know about the Universe, we have just barely scratched the surface. Life is a constant journey of learning and, hopefully, imagination.
Colour is the tiny visible portion of the vast spectrum of electromagnetic energy which is one of the four fundamental forces of the universe. Light functions at the subatomic (quantum) level of matter as well as filling the whole space (as microwave background radiation - -an echo of the Big Bang of cosmic creation). All life on earth depends on the nutritious energy of light from the sun, which is conveniently stripped of dangerous levels of ultraviolet radiation by the earth’s atmosphere.
The color of light from an object changes by a very small amount, depending on whether the object is moving closer to us or further away. By the way, an object has to be moving very, very fast in order for the light to change color even a little.
If a star is moving closer to us, the light it gives off gets squeezed together, which makes it appear bluer than it actually is. If the star is moving away from us, the light gets stretched out, which makes it appear more red than it really is. If the star is also going faster all the time, or accelerating, this effect is even greater.
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Colours in Space
• The colour of an object in fact consists of a mixture of these light particles that are absorbed, then emitted by this object, and reach our eyes. The colour of an object that does not emit light itself but reflects the light it receives from the sun depends both on the light it receives and the change it makes on this light. If the object illuminated with white light appears "red", this is because it absorbs a large portion of the mixture that arrives to it from the sunrays and emits only red.
• The night sky has always appeared strangely colourless to the eye, however it requires modern imaging techniques to reveal the colours which tell us of the origin and destiny of the stars.
• The universe started out young and blue, and grew gradually redder as the population of evolved 'red' giant stars built up. The rate of formation of new stars has declined precipitously in the last 6 billion years due to the decline in reserves of interstellar gas for forming new stars. As the star-formation rate continues to decline and more stars become red giants the color of the Universe will become redder and redder. Eventually all stars will disappear and nothing will be left but black holes. These too will eventually evaporate via the Hawking process and nothing will be left except for old light, which will itself redden as the Universe expands forever.
• A blue-white star, like Sirius. Since the light it gives off has a lot of blue in it, the pitch, or frequency, of the light is high, which is shown by how close together the waves of light are. Arcturus represents a red star, like. The light it gives off is red, which is shown by how far apart the waves of light are. Remember, the closer together the light waves are, the higher the frequency, and the more blue the light is. The further apart the light waves are, the lower the frequency and the light is more red. If you go back to the piano example we used above, the lower notes on the piano would be red and the higher notes would be blue.
• Scientists can find out what a star or other object is made of and how hot it is by studying the light that it gives off. When scientists determine what the star is made of and how hot it is, they can also determine what color of light the star should be giving off. Once they have found this out, scientists can the determine whether the star is moving towards us or further away by whether the light is "blue shifted" or "red shifted" If the light is "red shifted" the star is moving away from us. If it is "blue shifted", it is moving closer.
The planets are individual worlds which reveal signs of their histories on their surfaces and in their rocks and ices. Most of the Solar System is fairly narrow in color range with yellow-brown grays of varying brightness and saturation predominating. The exceptions, such as the orange planet Mars, the sulfurous surface of Io or the blue oceans of Earth have been the focus of my efforts to obtain some color information to assist my portrayals of these worlds .
The planets and their moons are bright and dark, colorful and dull. Variations of color and brightness distinguish many of the bodies of the Solar System, and a few stand out as unique. The brightness, or percentage of the light reflected from a world is expressed as its 'albedo'. In the images I have tried to correctly color balance the image and present plausible contrast levels. No effort has been made to brighten or darken any of the images to maintain absolute brightness with any of the others.. |
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Symphony of colours
Summing up the light emitted at different wavelengths by all galaxies at a given cosmic epoch, the astronomers could then also determine the average colour of the Universe (the "cosmic colour") at that epoch. Moreover, they were able to measure how that colour has changed, as the Universe became older. The cosmic colour is getting redder with time. In particular, it was much bluer in the past; now, at the age of nearly 14,000 million years, the Universe has a kind of beige colour.
Color is not what most astronomers and physicists think it is. It involves hue, saturation and brightness, he instructs, and it can't be thought of as just a wavelength or a frequency. Researchers transformed an array of colors, replacing each wavelength into the color the human eye sees at that wavelength, and varying the intensity of the color in proportion to that wavelength's intensity in the universe.
The very vocabulary of astronomy is riddled with misleading color terms. Red giant stars like the bright and popular Betelgeuse, for example, are not really red, though they can sometimes appear so from Earth. The star's light would overwhelm the color-sensing cones in your eyes. Only from a great distance, when the star is relatively dim, can the cones sometimes detect a hint of red. The vast majority of red giants, however, set off only the rods in your eyes, which cannot detect color at all. So most stars appear white, regardless of how they are classified.
Different gases, such as oxygen, hydrogen and nitrogen, each generate a different wavelength, or color, depending on the local physical conditions.
Human eyes, even if very near to or inside one of these nebulae, could not make out the colors, however, because the emissions are too faint. They would see little more than a big gray area.
Observing the brightest deep sky objects through a large aperture telescope can just begin to show the colors of a few of these, although most of the time one can just distinguish between bright reflection nebulae and emission nebula only when seen adjacently.
Since the emission nebulae have a prominent emission line near the peak of the eye's response in the green, that color visually appears in the brightest such nebulae. Usually reflection nebula appear a more neutral gray. A few objects such as the Orion nebula are bright enough to just begin to stimulate color vision in a large telescope. Most people can distinguish the green of the 'core' regions, but the other reddish hues are faint and only visible through large telescopes.
Colour is in fact a quantitative thing, a numerical difference between brightness measurements in well-defined wavelength bands, though it may not have much relationship to perceived color.
The color of objects that astronomers release are not really representative of a thing one might imagine exists, which is the objective color of a star or a galaxy. Color is a very, very subjective phenomenon, he said. Color is in the eye of the beholder.
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