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1,000,000,000,000,000.
The indivisible unit in which waves may be emitted or absorbed.
The theory that describes the interactions of quarks and gluons.
Quantum Efficiency
Quantum Mechanics
General term for ideas based on
microscopic world that human eyes can't see or feel with our hands. In this
world, there is phenomenon, such as matter that is wave as well as being
particles that you can't explain with the rules in the world that you can see.
A (charged) elementary particle that feels the strong force; protons and neutrons are composed of three quarks each.
A quasi-stellar radio source. These peculiar objects emit radio waves with a large red shift. The red shift represents the fraction of the percentage in which the wavelengths are switched. Quasars are very far away, and very bright, and many astronomers agree that giant black holes are present within these objects.
Quasi-Stellar
Source (QSS)
1,000,000,000,000,000,000.
The technique of bouncing radio waves off an object to measure its distance or map its surface.
The movement of a celestial body toward or away from an observer.
Radial Velocity Curve
Radian
(rad)
Radiant (of meteor shower)
Electromagnetic wave which is emitted by a matter in order to emit light/heat. Example is Sun's rays.
Regions of charged particles in a magnetosphere.
Radiation Pressure
Radio
Radioactive Dating
The property possessed by some elements (as uranium) of spontaneously emitting alpha or beta rays and sometimes also gamma rays by the disintegration of the nuclei of atoms.
A radio-luminous galaxy. Radio galaxies are a part of a larger group of galaxies called active galaxies. The "active" refers to the fact that the observed radiation source is non-thermal: Glowing matter does not radiate this "active" luminous component. Furthermore, radio galaxies are named so because they are "louder" at radio wavelengths than at visible light wavelengths. This indicates tremendous activity within radio galaxies...something must be driving the non-thermal emission. Radio telescopes show lobes of radio emission extending millions of light years, centered at the nucleus of some radio galaxies, called extended radio galaxies. Centaurus A is a nearby example of an extended radio galaxy that features two outer lobes 650,000 and 1,350,000 light-years in diameter. Compact radio galaxies emit radio lobes not much larger that the galactic nucleus.
Instead of gathering
and focusing visual wavelength light, a radio
telescope collects
radio
wavelength light with a huge dish-shaped antenna. An array of radio telescopes
called the Very Large Array lies 80 kilometers west of Soccoro, New Mexico. VLA
radio telescopes are arranged in a "Y" pattern with each arm
supporting nine 25-meter parabolic dishes. These radio telescopes probe the
galaxy and universe where optical telescopes cannot. Astronomers have mapped the
hydrogen content of our galaxy, and discovered enormous activity and structures
in other galaxies invisible to optical telescopes.
Electromagnetic radiation with very long wavelengths, produced by gas clouds and energetic objects.
A straight line joining the center of an attracting body with that of a body describing an orbit around it; for example, a line joining the Sun and a planet.
Rayleigh
Criterion See also: Resolving Power.
Rayleigh-Taylor
Instabilities
Red Giant
The Doppler effect shifting light wavelengths to the red end of the spectrum because of the motion of the source. A red shift indicates a receding source of light, with the magnitude of the shift corresponding to the velocity of the source. Astronomers relate red shifts to a calibrated distance in order to stretch their cosmic yard stick beyond the local realm of galaxies. Planetary astronomers observe small red shifts and blue shifts in stars that unseen planets orbit.
Reflection
Law
A telescope that forms an image with mirrors.
A change in the direction of light that depends on incident angle, wavelength (color), and the material. Raindrops refract light into rainbows. Each color is a different wavelength that refracts at a unique angle, forming a band of color in order of wavelength: red, orange, yellow, green, blue, indigo, and violet. A prism behaves the same way using glass instead of water. The refraction happens at the boundary between two different, transparent materials.
Region.
The layer of rocky debris and dust made by meteoritic impact that forms the uppermost surface of planets, satellites and asteroids.
Relativity,
General Theory of
Resolution
(Spatial)
Resolution
(Spectral or Frequency)
A measure of a telescope's ability to distinguish fine detail.
A relationship in which the orbital period of one body is related to that of another by a simple integer fraction, such as 1/2, 2/3, 3/5.
Reticular (net-like) pattern.
The rotation or orbital motion of an object in a clockwise direction when viewed from the north pole of the ecliptic; moving in the opposite sense from the great majority of solar system bodies.
An apparent backward movement of a superior planet in the sky, as Earth overtakes it on its journey around the Sun.
An elongated valley formed by the depression of a block of the planet's crust between two faults or groups of faults of approximately parallel strike.
The position of a celestial object in the sky east of the vernal equinox along the celestial equator. Sidereal hours, minutes and seconds divide the celestial equator from 0 to 24 sidereal hours of right ascension. Keep in mind that the celestial equator is a projection of Earth's equator onto the sky, and Earth's rotation period is 24 sidereal hours (23.9345 solar mean hours). Thus dividing the celestial equator into sidereal hours, minutes and seconds instead of 360 degrees makes some intuitive sense. Set 1 sidereal hour equals 15 degrees to convert between right ascension and degrees.
The closest a fluid body can orbit to its parent planet without being pulled apart by tidal forces. A solid body may survive within the Roche limit if the tidal forces do not exceed its structural strength. The Roche limit is calculated with the equation:
RL = 2.456*R*(p'/p)^(1/3)
Where p' is the density of the planet, p is the density of the moon, and R is the radius of the planet.
Roche
Lobe
Rotation
The term applied to scarps on planetary surfaces; many scarps are thought to be the surface expression of faults within the crust of the planetary object. |