Exosphere Dictionary of astronomy, letter E It is the outermost part of the Earth's atmosphere that extends above 600 km in height. It is very rare and does not have a defined upper limit since, simply, the density decreases gradually until the total disappearance of the atmosphere.

Sunspots If the temperature of the solar surface is so high that it is white, why are the sunspots black? To be black they would have to be cold, and how can there be something cold in the Sun? The question, as formulated, seems like a real catch. In fact, in the early nineteenth century the great astronomer William Herschel concluded that sunspots had to be cold because they were black.

Titan is the largest satellite on the planet Saturn. It seems that it is the only astral body that, next to Earth, has liquid on its surface. But its seas have methane instead of water, and many scientists believe it could house some form of life. Investigations conducted by the Cassini Probe on Titan have revealed that a part of the surface of this moon of Saturn had shifted from its position about 30 kilometers.

Hale (observatories) Dictionary of astronomy, letter H Name given from 1970 to the two great American astronomical observatories of Mount Wilson and Mount Palomar, in honor of astronomer George Hale. Both are under the aegis of the Carnegie Foundatior and the California Institute of Technology: the first is 32 km northwest of Los Angeles and the second 80 km northeast of San Diego, in California, United States.

Carbon-Nitrogen-Oxygen Cycle Astronomy Dictionary, letter C Carbon Oxygen Nitrogen Cycle is known as one of the two series of nuclear reactions that supply energy to a star of the first magnitude. The carbon cycle begins and ends with a carbon core 12 that acts as a catalyst in the production of a helium core from hydrogen nuclei; Neutrinos and gamma rays are also produced.

William Herschel (1738-1822) was a British nationalized German astronomer who made numerous and important contributions in the field of astronomy. Herschel's interest in astronomy did not manifest until he was 35 years old. With the help of his sister Caroline and his brother Alexander, he built an excellent reflection telescope, using a foundry that he installed in his house.