2.2 astronomy

• nuclear fusion: a process in which two small nuclei join to form a larger nucleus, releasing energy
• refraction: a bending in the direction of a wave that occurs when the wave changes speed
• reflection: a return of a wave from a boundary
• polarization: confining a wave to vibrate in one direction
• diffraction: the bending of a wave as it passes by obstacles or by the edges of an opening
• diffraction pattern: a pattern produced by waves that have underdone diffraction
• resolution: the amount of small detail visible in an image; low resolution means only large features can be seen, high resolution means small details can be seen
• false-colour image: an image that depicts an object in colours that differ from how a person would see the same object using only his or her eyes; often used to produce images using emr outside of the visible spectrum
• multiwavelength astronomy: the study of objects in space using the principle that these objects reveal diffrent aspects of their behaviour through the many wavelengths of emr they emit
• very large array: a group of radio telescopes distributed over many kilometers along the arms of a Y-shaped track
• diffraction gratin: a piece of glass or plastic with thousands of tightly spaced lines etched in its surface; used to produce spectra
• continuous spectrum: a spectrum having no distinct lines that is distributed over an inbroken band of wavelengths
• absorption spectrum/dark line spectrum: a spectrum that has a pattern of dark lines due to the light passing through an absorbing medium; can be used to identify a material
• emission spectrum/bright line spectrum: a spectrum that has a pattern of separate bright lines that is emitted from an excited gas under low pressure; can be used to identify a material
• spectrometer: an optical instrument used to measure wavelengths of light
• doppler effect: a change in the observed frequency of a wave due to motion between the source and the observer
• blue shift: an increase in frequency due to a source EMR moving toward an observer, due to the doppler effect
• red shift: a decrease in frequency due to a source of emr moving away frim an observer, due to the doppler effect
• red giant: a star of great size and age, relatively low surface temperature
• nebula: an interstellar cloud of gas and dust
• supernova: a stellar explosion that produces a very bright cloud of ionized gas that remains a very bright object in the sky for weeks and months
• white dwarf: a compact star found as the last stage in the evolution of low-mass stars
• neutron star: super-dense star consisting mainly of neutrons formed as th last stage in the stellar evolution of intermediate-mass starts
• pulsar: a rotating neuron star that emits radiation in regular pulses
• black hole: an area in space with a gravitational field so strong that neither matter nor emr can escape; formed as the last stage in the evolution of high-mass stars.