Glossary

  • Asteroid (planetology): A body smaller than →planets and →dwarf planets but larger than →meteoroids. Orbits the →Sun inside the orbit of Neptune. Typically of rocky or iron composition, but may also be partially icy. Sometimes called (incorrectly) a planetoid or a plametesimal. The boundary between →comets and asteroids is indeterminate.
  • Big Bang (physics): The event in which all the matter and energy, as well as time were formed. Grounded in observations of galaxies moving away from us, and extrapolation of that backwards in time.
  • Astrobiology (astrobiology): Field of science that investigates the basic questions of life: its emergence, necessities and development, as well as possibilities of life on other planets. Interdisciplinary field uses methods of astronomy, biology, biochemistry, →geology, physics, chemistry, etc.
  • Bolide (planetology): →meteor
  • Chemosynthesis (biology): A method of storing energy obtained from oxidising inorganic molecules in the chemical bonds of organic compounds. See also →photosynthesis.
  • Climate change (geophysics): A significant statistical change in climate. Caused by, for example, significant changes in either the activity of the →Sun, the orbit of the →Earth, the positions of crustal plates, volcanic activity, or biological activity.
  • Comet (planetology): A body orbiting the →Sun in a very elliptical orbit. Typically of largely icy composition. Once near the Sun part of the comet will be constantly vaporized / ejected into space, forming the characteristic tail and a diffuse halo (coma). The boundary between comets and →asteroids is indeterminate.
  • Cultural evolution (history): The evolution and changes in the skills, knowledge and customs of a society across generations. Somewhat comparable to biological →evolution.
  • Dwarf planet (planetology): A roughly spherical body orbiting the →Sun. The difference between a dwarf planet and a →planet is that a dwarf planet is not massive enough to dominate its orbit. Hence its orbit is shared with other unbound objects of significant size. Of the Solar System objects five are approved dwarf planets (Ceres, Eris, Haumea, Makemake, Pluto), and 3–50 objects fullfill the criterion.
  • Earth (planetology): Our own →planet, also called Tellus. The largest solid surface body in the Solar System, and the fifth largest planet. The only body in the universe known to harbor life.
  • Exomoon (astronomy): A →moon in the sphere of influence of another star than the →Sun.
  • Exoplanet (astronomy): A →planet orbiting a star other than the →Sun.
  • Evolution (biology): Generation-based changes in the inherited traits of organisms. Operates through natural selection, mutations, genetic drift and genetic hitchhiking, and gene flow. Compare with →cultural evolution.
  • Fireball (planetology): →meteor
  • Galaxy (astronomy): A large structure in space, held together by gravitation. Consists of stars, gas, dust, and dark matter. Usually assembled together by gravity into galaxy groups (few to tens of galaxies), galaxy clusters (tens to thousands of galaxies), and superclusters (several galaxy clusters). The proper noun Galaxy refers to our own →Milky Way galaxy.
  • Galaxy cluster (astronomy): galaxy
  • Galaxy group (astronomy): galaxy
  • Galaxy supercluster (astronomy): galaxy
  • Geologic time scale (geology): A method of measuring the relationships of events and phenomena in the past. Divides the history of the planet into eons, eras, periods, epochs and ages. Based on stratigraphical relationships.
  • Geology (geology): Field of science studying bedrock, rocks and soil, and the processes forming and modifying them. Examines the history, structure and composition of the →Earth.
  • Great apes (biology): Our own species and its closest relatives. →Taxonomic family Hominidae of the order primates. Includes eight extant species: Bornean, Sumatran and Tapanuli orangutan; eastern and western gorilla; as well as three →hominin species (bonobo, common chimpanzee, and →human), and in addition several extinct species.
  • Hominid (biology): →great apes
  • Hominidae (biology): →great apes
  • Hominin (biology): Our own species and its closest relatives. →Taxonomic tribus Hominini, belonging to the family of →great apes. Includes genus Homo and extinct subtribus Australopithecina, and according to some also genus Pan (i.e., chimpanzees).
  • Hominini (biology): →hominin
  • Homo (biology): Our own species and its closest relatives. →Taxonomic genus of the →hominin tribus in the family of →great apes. Includes several extinct species (e.g., H. habilis, H. erectus, H. heidelbergensis, H. neanderthalensis, H. florensis), and the extant H. sapiens (→human).
  • Homo sapiens (biology): →human
  • Human (biology): Our own species, Homo sapiens. Belongs →taxonomically to class mammalia, order primates, family →great apes, tribus →hominini and genus Homo (of which it is the only extant species). The most widely spread species of all animals. Closest extant relatives are the common chimpanzee and the bonobo.
  • Life (biology): A characteristic found in beings sustaining biological processes. Defining life univocally is difficult. Shared traits in living organisms include, e.g., cell-based metabolism, growth and reproduction, and the inheritance of DNA/RNA based information. All life we know of originates from Earth, and is based mainly on carbon, hydrogen, nitrogen and oxygen.
  • Meteor (planetology): A bright streak of light in the night sky. Occurs when a small →meteoroid enters the atmosphere of a planet or a moon and compresses and ionizes the gas in front of it. Known also as a shooting star. A very bright meteor is known as a fireball or a bolide.
  • Meteorite (planetology): A rock fallen from space onto the surface of the Earth. Can be distinguished from its thin fusion crust when fresh. A piece of →meteoroid, →asteroid, →comet, or another solid surface →planet or →moon.
  • Meteoroid (planetology): A small piece broken off a →comet or an →asteroid, and now orbiting the →Sun independently. Upper limit of the size is usually 1–10 metres. When impacting with →Earth the meteoroid is visible as a →meteor, and the part that survives to the ground is known as a →meteorite.
  • Milky Way (astronomy): Our own galaxy. Barred spiral galaxy, with 100–400 million stars and a diameter of 150 000–200 000 light years. →Sun is located ca. 26 000 light years from the galactic centre, where lies a ca. 4 100 000 Solar mass black hole (Sagittarius A*).
  • Moon (planetology): A body bound to and orbiting a larger body (e.g., →planet, →dwarf planet, →asteroid, or transneptunian object) that in turn orbits the →Sun. Also known as a satellite. The proper noun Moon refers to the natural satellite of our own planet →Earth.
  • Paleontology (paleontology): Field of science studying the history of life, especially through fossil evidence. Interdisciplinary field mainly between geology and biology.
  • Photosynthesis (biology): Using solar radiation to store energy in the chemical bonds of organic compounds. Photosynthesis is done by green plants, cyanobacteria, and algae. See also →chemosynthesis.
  • Planet (planetology): A roughly spherical body orbiting the →Sun, and massive enough to dominate its orbit so that no other unbound large bodies may orbit near it. There are eight planets in the Solar System: Mercury, Venus, →Earth, Mars, Jupiter, Saturn, Uranus and Neptune. See also →dwarf planet, →exoplanet.
  • Planetology (planetology): Field of science studying the solid surface bodies in the Solar System (→planets, →dwarf planets, →asteroids, →comets, →moons). Interdisciplinary field uses methods of astronomy, →geology, physics, chemistry, etc.
  • Satellite (planetology): →moon
  • Shooting star (planetology): →meteor
  • Snowball Earth (geophysics): A chapter in →Earth‘s history, when the surface was (almost) entirely covered by ice.
  • Sun (astronomy): Our nearest star and the centre of the Solar System. →Earth orbits the Sun at a distance of 149 million kilometres (1 astronomical unit or 1 au or 8,3 light minutes).
  • Supercluster (astronomy): galaxy
  • Systematics (biology): →taxonomy
  • Taxonomy (biology): Field of science studying the kinship, definition, and categorization of organisms. Systematics is the theoretical study of the same topics.
  • Tellus (planetology): →Earth