Download 8th Grade - Astronomy

8th Grade Astronomy Core Science Vocabulary
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Rocky objects revolving around the sun that are too small and numerous to be
considered planets. Most asteroids revolve around the sun in circular orbits between
the orbits of Mars and Jupiter. This (p. 574)
A unit of measurement equal to the Earth’s average distance from the sun,
Astronomical approximately 150 million kilometers. Astronomical unit is abbreviated as 1 AU. The
Unit
term is used primarily to describe the distances between objects in the solar system.
Example: Saturn is 9.6 AU from the sun. (p. 543)
The Big Bang is the initial explosion that resulted in the formation and expansion of the
Big Bang
universe. Astronomers theorize that the universe began approximately 13 billion years
Theory
ago when an incredibly hot, dense singularity exploded in an immense blast. Matter,
stars and galaxies formed as the universe rapidly expanded and cooled. (p. 622)
A loose collection of ice, dust, and small rocky particles, typically with a long, narrow
elliptical orbit around the sun.
The inner rocky core of the comet is called the nucleus.
Comet
Clouds of gas and dust that form around the nucleus are called the coma.
As a comet heats up as it approaches the sun, some of its gas and dust stream
outward forming a tail.
Most comets originate in the Kuiper Belt and the Oort Cloud in the far reaches
of the solar system. (p. 573)
The partial or total blocking of one object in the space by another.
A solar eclipse occurs during a new moon when the moon lies between the
sun and the Earth blocking the sun’s light from the Earth.
A lunar eclipse occurs during a full moon when the Earth blocks light from
Eclipse
reaching the moon.
The umbra is the very darkest part of the moon or Earth’s shadow. Only people
within the umbra experience a total eclipse.
The penumbra casts a larger shadow that is less dark. People in the penumbra
experience a partial eclipse. (p. 481)
A huge group of stars, star clusters, star systems, dust and gas bound together by
Galaxy
gravity. There are billions of galaxies in the universe each with billions of stars.
Astronomers classify galaxies into three main categories: spiral, elliptical and
irregular. Our own galaxy is called the Milky Way and is a spiral galaxy. (p.617)
Hertzsprung- A graph used to represent the relative surface temperature and absolute brightness of
Russell
stars. The H-R diagram also includes color (red, red-orange, yellow, white and blue)
Diagram
and relative size. (p. 604)
The distance that light travels in one year; about 9.5 million million kilometers (4.6
trillion miles). Astronomers use the light-year to measure distances between the stars.
Light-year
Light travels at about 300,000 kilometers a second. A light-year is a unit of distance
not time. Example: Our next nearest star neighbor is Proxima Centauri which is 4.2
light-years from Earth. (p. 602)
The apparent change in position of an object when seen from different places
Astronomers use parallax to measure distances to nearby stars by measuring the
Parallax
apparent movement or shift in a star’s position when seem from Earth at two different
times of the year such as January and July. (p. 602)
The movement of an object around another object. One complete revolution of the
Revolution
Earth around the sun takes 365.25 days or one year. The moon revolves around Earth
in approximately 28 days. (p. 465)
The spinning motion of a planet on its axis. The rotation of the Earth on its axis causes
Rotation
day and night as the Earth rotates eastward. The Earth takes approximately 24 hours
to rotate once on its axis. . (p. 465)
Any object that orbits around another object in space. The moon is a natural satellite of
Satellite
the Earth. An artificial satellite is a device that is launched into orbit around the Earth
or another planet. Artificial satellites are designed for many purposes such as
communications, military intelligence, weather and geographical data. (p. 405; 511)
Asteroid
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Solar System
The Solar system consists of the sun, the planets and their moons, and several kinds
of smaller objects that revolve around the sun such as comets, asteroids and dwarf
planets. The sun is the source of visible light in the solar system. The planets and
moons are visible because sunlight reflects from their surfaces. (p.543)