Page 47 - Curriculum Visions Dynamic Book

galaxy A system of stars and interstellar matter within the Universe.
gravitational field The region surrounding a body in which that body’s gravitational force can be felt.
gravity The force of attraction between bodies.
light-year The distance traveled by light through space in one Earth year, or 63,240 astronomical units.
photon A particle (quantum) of electromagnetic radiation.
space Everything beyond the Earth’s atmosphere.
star A large ball of gases that radiates light. The star nearest the Earth is the Sun.
theory of relativity A theory based on how physical laws change when an observer is moving. Its most famous equation says that at the speed of light, energy is related to mass and the speed of light.
Universe The entirety of everything there is; the cosmos.
 Wherever you look in the sky with a powerful telescope, you will find galaxies. This is a massive cluster of galaxies called Abell 2218. It is in the constellation Draco, some 2 billion ligHt-years from Earth.
The cluster is so massive that its enormous gravitational field bends
light rays passing through it, much as an optical lens bends light to form an image. This phenomenon magnifies, brightens, and distorts images from faraway objects just as a powerful “zoom lens” does. As
a result, we can see distant galaxies that could not normally be observed with the largest telescopes. In this picture you
can see spiral and elliptical galaxies. The yellow-white colour of several of the galaxies represents the combined light of many stars.
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