Astronomy Detectives

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angular momentum: the product of the mass of an object in motion times its velocity, as measured about a fixed axis.
arcsecond: a unit of angular measure equal to 1/3600 of a degree.
AU: astronomical unit; a unit of measurement based on the mean distance between the Earth and the Sun, equal to roughly 1.5 billion kilometers or 900 million miles.

blueshift: a decrease in the wavelength of radiation emitted by a celestrial body as a result of motion of the body toward the observer.

constellation: an arbitrary configuration of stars within some region of the sky, often named after an animal, object, or mythical figure.

doppler effect: an apparent shift in the observed wavelength (or frequency) of a wave due to relative motion between a source and an observer.

frequency: the number of oscillations of a signal (such as a light wave) that pass a given point in a certain period of time. The frequency of a light wave is equal to the speed of light divided by the wavelength of the radiation.

galaxy: an enormous assemblage of stars, star clusters, gas, and dust bound together by its own gravity.

infrared: the portion of the electromagnetic spectrum between the visible and the radio; infrared light has wavelengths in the range of roughly 0.75 to 350 millionths of a meter.
interstellar medium: material comprising gas and dust that permeates the space between the stars in the galaxy.

Kleinmann-Low Young ProtoStellar Object (KaLYPSO): an acronym devised to describe the newly forming, massive star "Source I", located in the Kleinmann-Low Nebula in the constellation of Orion.

light-year: the distance that light moving through empty space will transverse in one year; it equals approximately 5.9 million miles or 9.5 million kilometers.
low-Earth orbit: a satellite orbit between roughly 90 to 600 miles in radius.
low-mass star: a star with a mass less than approximately 2-3 times the mass of the Sun.

maser (Microwave Amplification by Stimulated Emission of Radiation): a type of radiation that occurs under special conditions where atoms are induced to emit radiation in a focused beam over a very narrow range of wavelengths. A maser is the radio wavelength equivalent of a laser.
Milky Way: the home galaxy of our Sun and solar system.

near-infrared light: the portion of the infrared spectrum extending from roughly 0.75 to 5 millionths of a meter.
nebula: a diffuse interstellar cloud made of gas and dust.

radio spectrum: a measurement of the strength of a radio signal as a function of frequency or wavelength.
redshift: a shift of radiation to longer wavelengths caused by motion of a radiation source away from an observer.
resolution: the degree to which the fine details of an object can be seen or separated. The resolution of a telescope is proportional to the wavelength of the light being studied, divided by the diameter of the telescope.

spectrometer: a device that disperses the radiation from a source to permit the study of the strength of its signal as a function of wavelength.
spiral arms: arms comprised of gas, dust, and young stars that wind out from the center of a spiral galaxy.
spiral galaxy: a flattened, rotating galaxy whose youngest stars often appear to trace a pinwheel-like shape.
star cluster: a group of stars that are held together by their mutual gravitational forces.
star-forming region: a region in a galaxy containing clouds of cold, dense gas in the process of collapsing to form new stars.

visible light: light in the part of the electromagnetic spectrum that is visible to the human eye (also called optical light) and which has wavelengths between roughly 380 to 750 nanometers.
VLBI (Very Long Baseline Interferometry): a technique in which the signals from two or more widely separated telescopes are recorded and combined at a later time to produce images of the sky with extremely high angular resolution. The resulting resolution of the images is comparable to that of a single telescope whose diameter is equal to the separation of the individual telescopes.