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The observable universe
Even with the most advanced technology, we were only able to see a small part of the universe. Observable universe is called, and is the part of the Cosmos whose light has had time to reach us.
The observable universe has a sphere, with the Earth at its Center. So we can see the same distance in all directions.
The boundary of the observable universe is called cosmic light horizon. The objects on the horizon are the farthest we can see. Its light left for us almost since the origin of the universe, 13.7 billion years ago. So that we see them as they were made more than 13,000 million years. Why they are so important to know the evolution of the universe.
But, as the universe expands, in fact these objects are much further away. Currently, they are already 46,500 millions of years light.
Nearby visible, ultraviolet and infrared light
Great observatories of NASATo explore the entire observable universe, NASA put in orbit four space telescopes: Spitzer, Hubble, Chandra and Compton. Each captures a different type of light. Currently, the Compton is no longer operating.
The observable universe at a glance
The part of the universe that we see with the naked eye is called the celestial sphere. It is an imaginary sphere, with the Earth in the Center, where the constellations are located. It reaches up to the 2'5 million of years light.
The furthest that can be seen is the neighboring Andromeda Galaxy, and the two satellite galaxies of the milky way: the small and the large cloud of Magellan. Everything else belongs to our Galaxy, the milky way.
Translation for educational purposes authorized by: Astronomía: Tierra, Sistema Solar y Universo