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- galactic cannibalism
- the swallowing up whole of a small galaxy by a
large galaxy (usually a large elliptical galaxy at the center of a galaxy cluster).
- galaxy
- a very large cluster of stars (tens of millions to trillions of
stars) gravitationally bound together.
- General Relativity
- a theory invented by Albert Einstein to describe
gravity. It says that gravity is a warping or distortion of spacetime around
a massive object. Although it applies everywhere in the universe,
General Relativity must be used instead of Newton's
law of
gravity in regions of strong gravity.
- geocentric
- (universe): model of the universe with the Earth at the
center and all other objects moving around it.
- giant impact theory
- explanation about how the Moon was formed from mantle material blown
out by the impact of a Mars-sized (or larger) planet with the Earth
several billion years ago. The ejected material condensed to form the
Moon.
- giant molecular cloud
- large, dense gas cloud (with some dust)
that is cold enough for molecules to form. A typical giant molecular cloud has
a few hundred thousand to a few million solar masses of material. Stars form in them.
- globular cluster
- spherical cluster of hundreds of thousands to millions
of very old stars. The orbits of most globular clusters are very elliptical and
oriented in random directions.
- granulation
- bright spots of convection on the Sun's surface 700 to 1000
kilometers across forming a honeycomb pattern. Formed from hot, bright gas rising from
below in the center of a granule and cooler, dimmer gas falling back down at the
edge of a granule.
- gravitational lens
- the focusing of light from a distant object by the
warped space-time around a massive body (such as a galaxy) between you and the
distant object as predicted by General
Relativity.
- gravitational redshift
- the lengthening of the wavelength of
electromagnetic radiation as it moves away from a region of intense gravity.
- gravity
- a fundamental force of nature between two objects that is
proportional to the product of their masses and inversely proportional to the
square of the distance between their respective centers. It depends on
nothing else.
- greenhouse effect
- the trapping of heat energy close to a planet's
surface by certain types of gases in the atmosphere (e.g., water, methane, and
carbon dioxide). These gases allow visible light from the Sun to reach the
surface but prevent the infrared light from the heated surface to radiate back
to space.
- ground state
- the lowest energy state of an atom---all of the
electrons are as close to the nucleus as possible.
Glossary links (select a letter for definitions of astronomy terms
beginning with that letter):
A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z
last updated:
June 7, 2019
Is this page a copy of Strobel's
Astronomy Notes?
Author of original content:
Nick Strobel