What is a dark Nebula? | Earth, Solar System and Universe.

In cold areas of the Cosmos, where interstellar dust and gas are abundant, the material is concentrated and is huge icy clouds. Consist above all of hydrogen, which is the fuel of the stars. Gravity causes the material group together more and more. As it increases the amount of material, in the center of the Nebula pressure and temperature increase.
When pressure and temperature are high enough, the Nebula collapses. This means that it has just been born a star inside. The new star begins to heat up the cold cloud. When heated, the dark Nebula turns red and becomes an emission nebula.

Some dark nebulae

Dark nebulae only look like black spaces in front of a light background, normally an emission nebula. Some of the most well known dark nebulae are:
Horse head nebula: in the photo above, is the dark Nebula, most beautiful and famous for its curious shape of head of seahorse. It is in the constellation of Orion, a 1,500 years light-years away from Earth.
Coal sack nebula: is the most famous dark Nebula in the southern hemisphere. Cruz del Sur is a 600-year light in the constellation. It is easily recognised at first glance, like an unexpected dark area in the white band of the milky way.
Cone nebula: located at 2,500 years light-years from Earth, in the constellation of Monoceros. It forms a dark cone on top of the Christmas tree cluster. Interestingly, it was discovered on December 26.
Published for educational purposes