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An encyclopedia with expressions used in astronomy. Find out a lot about the universe and the processes that drive the evolution of the universe.
A Short History of the Universe
Read about the history of the universe from the Big Bang, the Cosmic Microwave Background and the Dark Ages up to the formation of our own solar system and the appearance of Homo sapiens.
Asteroids, meteoroids, meteors, meteorites, comets
What is the difference between asteroids, meteoroids, meteorites, meteors, meteor showers, fireballs, bolides and comets? Find out here!
Black body radiation
What kind of radiation does a star emit? After reading this article you will also know why cooler stars look red and hotter stars are blue.
Black hole
Black holes are objects so massive that they create a hole in space itself. Read about the types of black holes, their structure, accretions discs and jets.
Black Holes Q&A
What happens if you fall into a black hole? Are black holes gigantic vacuum cleaners? Are there black holes close to us? Check our black hole Q&A section.
When you read about a supernova or a neutron star you often read about degenerate matter. Why does this matter react so strangely? Find out in our article.
Electromagnetic spectrum
Visible light is just a tiny fraction of all the existing wavelengths. Learn about the whole spectrum by observing a galaxy via many different wavelengths.
Emission nebula
Some of the most beautiful images of our universe are photos of emission nebulae. Read about emission nebulae in Sun.org´s encyclopedia.
Discover the fascinating world of extra-terrestrial planets: what do they look like and may they be suitable for life? How many are there and how do we detect them?
Interstellar medium
Is there something between the stars or is there a complete vacuum? In our article about the interstellar medium you will get the answer.
Molecular Clouds and Dark Nebulae
Molecular clouds and dark nebulae contain all the ingredients to form stars, planets and even life itself. Find out the details in our article.
Neutron star
An object so dense that one tiny sugar cube of it weighs more than all human beings put together is definitely worth a closer look. Read more in Sun.org´s article.
Q&A – Astronomy and Space
How long would life persist on Earth without the Sun? How many stars are there in the universe? Read our astonishing Q&A section and be surprised!
Reflection nebula
A reflection nebula is a cloud of gas and dust reflecting light from other stars. Read Sun.org´s article about reflection nebulae to better understand them.
If you want to understand what a star is, how it was born and how it lives and dies, then don´t miss Sun.org´s fascinating article about stars.
You'll understand the driving forces causing these most violent explosions in the universe and get a vivid description of the explosion itself!
Units, Conversions and Numbers
How many km is one astronomical unit (AU)? How many kg in one solar mass? Find the most important astronomic conversion units used by Sun.org.