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| An object with such enormous gravitational force that nothing, not even light, can escape from within a specific distance from its center, called the objects black hole radius. |
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| The smallest electrically neutral unit of an element, consisting of a nucleus made of one or more protons and zero or more neutrons, around which orbit a number of electrons equal to the number of protons in the nucleus. This number determines the chemical characteristics of the atom. |
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| Molecules of CO2, which each have one carbon atom and two oxygen atoms |
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| The element that consists of atoms whose nuclei each have six protons, and whose different isotopes each have six, seven, or eight neutrons |
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| Matter of unknown form that emits no electromagnetic radiation that has been deduced, from the gravitational forces it exerts on visible matter, to comprise the bulk of all matter in the universe. |
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| an intrinsic property of elementary particles, which may be positive, zero, or negative; unlike signs of electric charge attract one another and like signs of electric charge repel on another through electromagnetic force. |
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| an elementary particle with one unit of negative electric charge, which in an atom orbits the atomic nucleus. |
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| The basic components of matter, classified by the number of protons in the nucleus. All ordinary matter in the universe is composed of ninety-two elements that range from smallest atom, hydrogen (with one proton in its nucleus), to the largest naturally occurring element, uranium (with ninety-two protons in its nucleus). Elements heavier than uranium have been produced in laboratories. |
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| The combining of smaller nuclei to form larger ones. When nuclei smaller than iron fuse, energy is released. Fusion provides the primary energy source for the world’s nuclear weapons, and for all stars in the universe. Also called nuclear fusion and thermonuclear fusion. |
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| A planet similar in size and composition to Jupiter, Saturn, Uranus, or Neptune, consisting of a solid core of rock and ice surrounded by thick layers of mainly hydrogen and helium gas, with a mass ranging from a dozen or so Earth masses up to many hundred times the mass of the Earth. |
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| the lightest and most abundant element, whose nuclei each contain one proton and a number of neutrons equal to zero, one, or two,. |
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| The Sun’s planets Mercury, Venus, Earth, and Mars, all of which are small, dense, and rocky in comparison to Giant Planets. |
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| A region of interstellar space considerably denser than average, typically spanning a diameter of sever dozen light years, with densities of matter that range from ten atoms per cubic centimeter up to millions of molecules per cubic centimeter. |
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| Gas within a galaxy not part of any stars. |
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| An atom that has lost one or more of its electrons. |
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| The distance that light or other forms of electromagnetic radiation travel in on year, equal to approximately 10 trillion kilometers or 6 trillion miles |
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| A stable grouping of two or more atoms. |
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| A diffuse mass of gas and dust usually lit from within by young, highly luminous stars that have recently formed from this material. |
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| – An elementary particle with no electric charge; one of the two basic components of an atomic nucleus. |
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| An elementary particle with no mass and no electric charge, capable of carrying energy. Streams of photons form electromagnetic radiation and travel through space at the speed of light, 299,792 kilometers per second. |
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| An object in orbit around another star that is not another star and has a size at least as large as Pluto, which ranks either as the Sun’s smallest planet, or as a Kupier Belt object too small to be a planet. |
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| elementary particle with one unit of positive electric charge found in the nucleus of every atom. The number of protons in an atoms nucleus defined the elemental identity of that atom. For example, the element that has one proton is Hydrogen. |
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| A star in formation, contracting from a much larger cloud of gas and dust as the result of its self-gravitation. |
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| A star that has evolved through its main sequence phase and has begun to contract its core and expand its outer layers. The contraction induces a greater rate of nuclear fusion, raises the stars luminosity, and deposits energy in the outer layers, thereby forcing the star to grow larger. |
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| A star that has evolved through its main sequence phase and has begun to contract its core and expand its outer layers. The contraction induces a greater rate of nuclear fusion, raises the stars luminosity, and deposits energy in the outer layers, thereby forcing the star to grow larger. |
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| The distribution of photon be frequency or wavelength, often shown as a graph that presents the number of photons at each specific frequency or wavelength. |
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| A mass of gas held together by its self-gravitation, at the center of which nuclear fusion reactions turn energy of mass into kinetic energy that heats the entire star, causing its surface to glow. |
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| galaxy with an ellipsoidal distribution of stars, containing almost no interstellar gas or dust, whose shape seems elliptical in a two-dimensional projection. |
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| A large group of stars, numbering from several million up to many hundred billion, held together by the stars mutual gravitational attraction, and also usually containing significant amounts of gas and dust. |
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| The galaxy that contains the Sun and approximately 300 billion other stars, as well as interstellar gas and dust and a huge amount of dark matter. |
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| The tiny remnants (less than twenty miles in diameter) of the core of a supernova explosion, composed almost entirely of neutrons and so dense that its matter effectively crams two thousand ocean liners into each cubic inch of space. |
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| The core of a star that has fused helium into carbon nuclei, and therefore consists of carbon nuclei plus electrons, squeezed to a small diameter (about the size of earth) and a high density (about 1 million times the density of water). |
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| A galaxy characterized by a highly flattened disk of stars, gas, and dust, distinguished by spiral arms within the disk. |
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| A star that explodes at the end of its nuclear-fusing lifetime, attaining such an enormous luminosity for a few weeks that it can almost equal the energy output of an entire galaxy. Supernovae produce and distribute elements heavier than hydrogen and helium throughout interstellar space. |
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| The scientific description of the origin of the universe, premised on the hypothesis that the universe began in an explosion that brought space and matter into existence approximately 14 billion years ago. Today the universe continues to expand in all directions, everywhere, as the result of this explosion. |
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| Forms of Energy in increasing order |
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| radio, microwave, infrared, visible/optical, ultraviolet, x-ray, gamma-ray |
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| Planets closest to furthest |
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| – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune ------- Pluto |
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