Planets have their own light

Corona: The outermost part of the solar atmosphere with low density and very high temperature. It is only visible from the ground during a total solar eclipse, as a kind of halo. The corona is the source of the solar wind.

Cosmic Radiation: Extremely high-energy atomic particles, mainly protons, which move through space at almost the speed of light. Cosmic rays also come from the sun sporadically, but the vast majority has its origin outside the solar system, probably in the galaxy.

Culmination: The maximum height of a celestial body above the horizon.

Luminosity: The total amount of energy emitted by a star in a unit of time.

Librations: Apparent oscillations of the moon, which mean that the moon can be seen from the earth from slightly different angles. This means that around 59 percent of the moon's surface can be observed. Light year A measure of distance that is defined as the distance that light travels in a vacuum in a year; it corresponds to 9.4607 x 10 to the power of 12 km or 63240 astronomical units. More common in astronomy is the parsec, which corresponds to 3.2616 light years.

Magnetosphere: Largely ionized, outermost part of a planetary atmosphere, in which the physical processes are essentially determined by the effect of the planetary magnetic field on the electrons and ions.

Meridian: A great circle through either the poles of the earth or the celestial sphere; especially the meridian running exactly north-south for the observer (local meridian, midday meridian).

Meteor: The tracer created when a small, solid, cosmic body (meteorite) collapses and burns up in the earth's atmosphere.

Meteorite: The solid body that creates a meteorological phenomenon; especially the non-burned remains that hit the surface of the earth. Meteorites offer the unique opportunity to study cosmic matter in the laboratory.

Occultation: The temporary covering of one celestial body (usually a star) by another (usually a planet or moon). A solar eclipse is a special case of an occultation.

Opposition: A planet is in opposition when the earth is on the planet-sun connecting line between the two. The opposition is the most favorable position for observing the planet.

Parallax: The apparent change in location of an object as a result of an actual change in location by the observer. By measuring the parallax, the distance to distant objects can be determined, for example stars from the "annual parallax" resulting from the movement of the earth on its orbit.

Parsec: Defined as the distance at which a star has an annual parallax of one arc second; this is 3 2616 light years or 3.0857 x 1013 km.

Penumbra: The area of ​​penumbra that arises around the umbra when illuminated with a light source of finite size; see also umber. The term is also used for the outer parts (the "courtyard") of sunspots.

Perihelion: The closest point in the orbit of a planet or comet to the Sun; the opposite point is called aphelion.

Phase cycle: The angle formed by the connecting lines sun - planet (or moon) and planet earth.

Photosphere: HeII (simply ionized helium) luminous layer that forms the visible surface of the sun.

Plague: Bright area of ​​the chromosphere in areas of activity (groups of spots) of the sun, which corresponds to the flares of the photosphere.

Planet: One of the nine medium-sized bodies (including the earth) orbiting the sun; also similar bodies in other fixed stars. Unlike the stars, the planets do not emit their own energy in the form of light and heat generated by thermonuclear reactions inside. The word "planet" is derived from a Greek word that means "wanderer". The planets move relative to the fixed stars. The orbit of a "lower" planet is within, that of an "upper" planet is outside of the earth's orbit. Polarization A special property of electromagnetic waves. In unpolarized radiation (for example visible light) the oscillation planes of the electrical as well as the magnetic component have any direction. With linear

Polarization: on the other hand, the vibrations only occur in one plane. The electrical oscillation plane is perpendicular to the magnetic one. Unpolarized radiation can be converted into polarized radiation with a polarizer. In addition to the linear, there are also "circular" and "elliptical" polarizations.

Quadrature: The position of the moon or an outer planet at 90 ° elongation.

Right scenario: The angle between the vernal equator and the point where the meridian through a celestial body intersects the celestial equator, measured eastward along the celestial equator in hours, minutes and seconds. Right ascension and declination indicate the position of the object in the sky.

Rochesche limit: The critical distance from the center of a planet within which larger bodies cannot exist because they break under the action of the tidal forces. For a satellite with the same density as that of the planet, the Roche limit is 2.4 planetary radii.

Saros: An interval (Saros period) of 6,583 days (equal to 18 years, 11.3 days), after which the sun, moon and earth take almost exactly the same relative position again. After a Saros period, therefore, eclipses of the same kind repeat themselves under similar circumstances.

Black body: A body that does not reflect any incident radiation, i.e. it completely absorbs it. It emits a (continuous) spectrum that is only determined by its temperature.

Main emphasis: Also the center of mass, is the center of gravity of a system of heavy bodies. The center of gravity of the earth-moon system lies within the earth.

Sidereal period: The duration of the orbit of a celestial body measured against the fixed star sky; see also Synodic Period.

Solar constant The amount of energy that is perceived in the form of solar radiation in one second on one square meter at the mean distance from the sun if there is no atmospheric absorption. Solstices The two points on the ecliptic with the greatest and the smallest declination of the sun; the time at which the sun reaches these points. On June 21st the sun has maximum declination (summer solstice or solstice), on December 21st it has minimum declination (winter solstice or solstice).

Sunspots: Dark, so cooler spots of various sizes and lifetimes in the photosphere, which usually appear in groups; their number fluctuates periodically (see solar cycle).

Solar system: The system consisting of the sun, the nine planets with their moons, the asteroids (small planets), comets and meteorites.

Solar wind: A permanent stream of particles, mainly of electrons and protons, emanating from the sun.

Solar cycle: The period of solar activity, which is manifested in the number of sotine spots, the frequency of the flares, and various other solar phenomena. The cycle has an average length of around 11 years.

Spectrum: The distribution of the radiant energy with the wavelength. In the optical range, the radiation is resolved into its spectrum with the help of a spectral apparatus. Visible, "white" light results in a "continuum" from violet to red, luminous gases only show individual bright "emission lines" at characteristic wavelengths; conversely, gases absorb light from a continuum under appropriate physical conditions and generate dark "absorption lines" (absorption spectrum, see also "Fraunhofer lines").

Stardate: System of time measurement based on the earth's sidereal period of rotation. The sidereal time is counted from the meridian passage of the vernal equinox.

Stratosphere: The region of the earth's atmosphere between the troposphere and the mesosphere (15 to 50 km altitude).

Synchrotron radiation radiation: which is emitted by electrons moving in strong magnetic fields at almost the speed of light.

Synodic period: The time interval in which, seen from the earth, the apparent positions of a planet relative to the sun (for example conjunctions) repeat.

Tektites: Small vitreous bodies found in a few, limited areas of the earth; its origin is still unclear: a connection with meteorite impacts is suspected.

Terminator: The boundary between the sunlit and dark hemisphere of a planet or moon.

Zodiac: A belt about 8 ° wide on both sides of the ecliptic, within which the sun and the planets move. It is divided into twelve zones of equal size, which are named after twelve constellations (signs of the zodiac).

Tropopause: The boundary between the troposphere and the stratosphere.

Troposphere: The lowest layer of the earth's atmosphere, in which the temperature decreases with altitude; it reaches up to about 15 km height.

Umbra: The dark center of a shadow ("umbra"); also used for the dark, central part of large sunspots. See also penumbra.

Zeeman effect: The splitting of spectral lines when emission or absorption occurs in the presence of a strong magnetic field.

Equation of time: The difference between true solar time and mean solar time varies between -14m24s and + 16m21s.

Zenith: The point on the celestial sphere directly above the observer