Radio telescope Dictionary of astronomy, letter R It is an instrument that serves as a receiver of radio waves from space. It can be constituted by a simple dipole-shaped antenna, connected to a sensitive amplification and recording device, or, and in most cases, by a basin-shaped structure (Paraboloid) that plays a totally analogous function to that of a mirror in a telescope: it concentrates the rays, in this case the radio waves, towards a focus.
Acceleration of gravity Astronomy dictionary, letter A The force of gravitational attraction causes an object in free fall on a celestial body to move, dispensing with possible atmospheric resistances, in an accelerated way, that is, with a constant increase in its velocity by unit of time, and that is directed towards the center of the celestial body.
Aerolito Dictionary of astronomy, letter A Literally, "aerial stone". An aerolith is a celestial body of a stony nature that penetrates the atmosphere and is recovered on the earth's surface. Aerolytes are pieces of disintegrated comets. Comet Biela, for example, disintegrated in its last step near Earth, and suddenly a true cloud of millions of aeroliths or "shooting stars" appeared, which dizzily crossed the sky for many hours.
Agglutinate (astronomy) Dictionary of astronomy, letter A In astronomy the word agglutinate refers to the union of several small bodies to form larger bodies. For example, the Earth was formed by agglutination or agglomeration of planetesimals, these in turn by agglutination of rocks of ice and stones and these by agglutination of dust.
Achromatic (lens) Astronomy dictionary, letter A In an achromatic lens the phenomenon of chromatic aberration has been corrected. Achromatic means lacking color. As the refractive index varies with the wavelength, the focal length of a lens also varies, and produces axial or longitudinal 'chromatic aberration'.
Charging coupling Astronomy dictionary, letter A Charging coupling is called a device that allows obtaining an electronic image of an astronomical element, enlarged hundreds of times with respect to optics. In one of its classic applications it is constituted by an integrated circuit board that is placed in the focal plane of a telescope.
Space agency Astronomy dictionary, letter A In the last years of the 50s, in order to coordinate the space programs and the activity of the various research centers dedicated to the exploration of space, both national and international organizations emerged. which, generically, is given the name of space agencies.
Black Hole Astronomy Dictionary, letter A A black hole is an object whose gravity is so great that the escape velocity is greater than the speed of light. The light that tries to escape from a black hole falls back on its surface just like a stone thrown into the air. Therefore, a black hole is invisible from the outside.
Albedo de la Tierra Dictionary of astronomy, letter A The albedo of the earth is known as the relationship between the luminous flux emitted by the surface of our planet and that which comes from the sun. This fraction of light varies with latitude and with the nature of the soil. Water reflects 10% of sunlight, vegetation 15% to 20%, sea ice 50% to 60%, recent snow 80% to 90%.
Alfa Centauro Dictionary of astronomy, letter A Alfa Centauro is the brightest star in the constellation of the Centaur and the most shining of the entire celestial vault after Sirius and Canopo. However, it is not visible from European latitudes because it shines in the southern sky. Observed with a telescope, what at first glance looks like a single star is revealed as a system formed by three suns that rotate around a common Center of gravity.
Alpha (particles) Dictionary of astronomy, letter A Alpha particles are nuclear particles that have a positive charge formed by a Helium nucleus, that is, two protons and two neutrons. Alpha particles are formed during nuclear processes that take place inside the stars.
Solar activity Astronomy dictionary, letter A Solar activity is usually called the phenomenon characterized by the presence of spots, bulges, glare and significant emissions in radio frequencies and X-rays in the Sun. Sunspots are yellow, although they would normally be dark spots.