The Apenninus Mountains are a prominent mountain range located in the northern hemisphere of the Moon. This great mountain range borders the southern part of the Mare Imbrium, while in the north it forms a border with the northern regions of Terra Nivium. The Apenninus mountains start next to the Eratosthenes crater, and end next to the Promontorium Fresnel.
Return (astronomy) Dictionary of astronomy, letter R It is the phase of space flight in which a spacecraft leaves its orbit to return to Earth. The first operation necessary for the return maneuver is the reduction of the orbital speed that, for an spaceship that flies in an orbit about 200 km high, is over 28.
Although surrounded by what may seem like smoke, the object known as "the flaming star" creates energy primarily from nuclear fusion, like other stars. Fire, typically defined as a rapid molecular acquisition of oxygen, occurs only when there is sufficient oxygen present and is not important in high energy and low oxygen environments such as that of stars.
Launch window Astronomy dictionary, letter V It is a time interval within which a rocket must be launched in order to reach the preset target. The optimal moment for launching a missile that, for example, has the function of placing an astronaut in a lunar path, is chosen in relation to the astronomical positions of the Earth and the Moon.
Many people have heard a sonic explosion, but few have seen it. When a plane travels at a speed greater than that of sound, the sound waves emitted by the plane cannot precede it and then accumulate like a cone behind the plane. When this shock wave passes, a spectator will hear a sound, a sonic explosion.
Dark matter Astronomy dictionary, letter M In recent years it has been discovered that there is a large amount of matter in the Universe that does not emit or absorb light (it is not seen), but it is known to exist because its gravitational effects on the stars are observed and the galaxies. Dark matter forms between 80% and 90% of the mass of the universe.
