Astrophysics — page 2 of 2

Astrophysics terms

101. Neutrino A lepton with no electric charge. Neutrinos participate only in weak and gravitational interactions and are therefore very difficult to detect.
102. Neutron A baryon with electric charge zero; it has the basic structure of two down quarks and one up quark (held together by gluons).
103. Nought Usually referring to the first value in a range, and denoted by a subscript, "0".
104. Nucleon Proton or neutron, part of atomic nucleus.
105. Nucleosynthesis The process by which atoms are formed by the coming together of subatomic particles and other smaller atoms.
106. Nucleus/Nuclei (plural- nuclei; adjective- nuclear ) The center of an atom. Nearly 100% percent of the mass of an atom is contained in the nucleus.
107. Observed Brightness The flux due to a light emitting object measured at the observer (in most cases, at the earth or a satellite).
108. Omega, Ω The ratio of the average total density of matter to the critical density required to make the universe flat and eventually stop its expansion.
109. Opaque to Radiation A condition when radiation is absorbed or scattered many times. For the first 400,000 years the universe was so hot that the matter was ionized and…
110. Open Universe , Ω A universe where the geometry of space is curved like an infinite saddle-shaped surface.
111. Parallax A method of finding astronomical distances. One uses a super distant background of stars as a reference plane, and observes the difference in position of…
112. Parsec A unit of distance, derived from a technique of finding distances to astronomical objects, called parallax. 3.1 x 1013 km or 3.26 light years.
113. Particle Accelerators A machine used to accelerate particles to high speeds, and thus, high energy compared to their rest-mass energy.
114. Particle Physics The study of fundamental particles (such as quarks and leptons) and the fundamental interactions (four forces).
115. Period Usually designated by T. This is the time interval of one complete oscillation of any wave. See Wavelength.
116. Phase Transition Change from one state of energy to another.
117. Photon A photon is both a wave and a particle. A beam of light is composed of these particles.
118. Planck Time The period of time immediately after the creation of the universe (10-43 s) during which quantum gravity is the principal phenomenon governing the…
119. Plasma (PLAZ-muh) The clear, yellowish, fluid part of the blood that carries the blood cells. The proteins that form blood clots are in plasma.
120. Positron The antiparticle of the electron, carry a charge that is opposite to an electron.
121. Primordial Nucleosynthesis Building of the atomic elements in the early universe when nuclei fused with one another. Most of the helium in the universe was created by this process.
122. Quantum Fluctuations Tiny changes in the energy of the vacuum.
123. Quantum Mechanics A theory of physics that is applicable to systems of extremely small scales (ie. the size of an atom). QM quantifies the "fuzzyness" of the universe.
124. Quark A fundamental matter particle that has strong interactions. Quarks have electric charge of either +2/3 (up, charm, top) or -1/3 (down, strange, bottom) in…
125. Quasar Short for Quasi-stellar Radio Source. A quasar behaves like a small galaxy powered by a super massive black hole, most of the time.
126. Radiation (RAY-dee-AY-shun) Energy released in the form of particle or electromagnetic waves.
127. Radiation Gas A mixture of photons and fast-moving charged particles.
128. Radiation-Dominated Universe When the density of radiation is greater than that of any other component.
129. Recede To move away from the observer, which is, in most cosmological instances, the earth.
130. Redshift A change in the frequency or wavelength of light. This can arise from motion of the source (Doppler shift), expansion of space, or strong gravitational…
131. Relative Brightness How bright one object is compared to another. If they have the same intrinsic brightness then the relative brightness tells us the ratio of distances to…
132. Relativity Galileo first developed the principle of relativity, being the postulate that the laws of physics should take the same form for all observers in uniform…
133. Relic Some thing left over from a previous time period. Remnant products or evidence of early physical eras.
134. Scalar A constant number. 1, -16, .3534, 7346 are all scalars.
135. Scatter When refering to photons and light, scattering describes the phenomenon of a source absorbing, and then emanating light in all directions.
136. Sensitivity When referring to a medical test, sensitivity refers to the percentage of people who test positive for a specific disease among a group of people who have…
137. Simultaneous Occurring at the same time.
138. Spacetime The theory of relativity says that time cannot be treated absolutely separately from space, only in one observer's relative view.
139. Spectra A range of different measurements. In terms of physics, spectra usually refers to the different wavelengths, or colors (if in the visible range) of light…
140. Spectral Line An emission (bright) or absorption (dark) of light at a specific frequency or wavelength.
141. Standard Candle A celestial object whose intrinsic brightness is known or can be estimated by some physical principle.
142. Static Unchanging over a length of time.
143. Steady State Theory A cosmological model where matter is created constantly as the universe expands so it remains homogenous and isotropic.
144. Stochastic Random.
145. Strong Force The interaction responsible for binding quarks, antiquarks, and gluons to make hadrons. Residual strong interactions provide the nuclear binding force.
146. Structure Changes in the shape of the bottom of lakes, rivers, or impoundments, especially those that influence fish behavior.
147. Super Cluster A cluster of clusters of galaxies. A vast collection of galaxy clusters that may contain tens of thousands of galaxies spanning over a hundred million…
148. Supernova Supernova refers to several types of stellar (meaning star) explosions that produce extremely bright objects that decline to invisibility over weeks or…
149. Synthesis of Nuclei Combining protons and neutrons to form nuclei.
150. Systematic Errors Measurement errors that are not random.
151. Type Ia Supernova Supernova formed from the explosion of an old, compact star (white dwarf). Used as standard candles as they have uniform intrinsic brightness.
152. Universe In the world of investments, the word universe refers to a specific group or category of investments that share certain characteristics.
153. Vacuum Energy A theorized energy everywhere in space, arising from quantum mechanics.
154. Variable Stars Stars which brighten and dim, some with precise regularity. For Cepheid variables, their period allows determination of their brightness, and so their…
155. Velocity The rate and direction of change of an object's position. The speed and direction at which something is moving.
156. Visible Mass Mass that gives off electromagnetic radiation, so that it can be detected. It is ordinary (baryonic) matter.
157. Visible Universe The part of the entire universe from which light would have had time to reach us in the age of the universe.
158. Wavelength The distance between one peak or crest of a wave (of light, heat, or other energy) and the next corresponding peak or crest.