Science 9 ACS Astronomy Unit Test

84 terms by cthiessen

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Mrs. Van Dop's Science 9 Class


is the science that studies the composition, position, and movements of all objects in space.


a scientist who studies astronomy


a pattern of stars arranged as a mythical figure or animal


are parts of constellations. The big dipper is part of the constellation ursa major

circumpolar constellation

three constellations that always appear in our night sky: Dig Dipper, Little Dipper and Casseopia.


He suggested the sun is the center of our solar system


the spinning of an object around an imaginary axis.


the number of hours of daylight


He constructed accurate telescopes and discovered moons and rings around planets.


when the earth is farthest away from the sun
(July 4)


he created the laws of planetary motion


when the earth is closest to the sun (Jan 3)


the change in direction of the Earth's axis


when the sun is above and below the horizon an equal amount of time


the part of the sun that is visible during a complete solar ecllopse. The outer atmosphere of the sun.


the view that the earth is the center of the universe

solar eclipse

the type of eclipse that occurs when it is sun, moon, earth

spring tide

very strong tides, very high and very low, when the sun,earth and moon are lined up


when the sun is at the highest and lowest positions in the sky

winter solstice

the day with the least hours of sunlight

summer solstice

the day with the most hours of sunlight


the motion of an object around another object (a year)

retrograde motion

the apparent slowing, reversal and looping of a planet in its path across the sky

lunar eclipse

Eclipse when it is sun, earth, moon


the view that the sun is the center of the solar system


Caused by the tilt of the earth's axis


caused by the gravitational pull between the earth and the moon and the sun.

neap tides

weak tides, when the sun and moon are perpendicular to each other with respect to the sun.

outer planet

one of the four planets furthest from the sun, the gas giants, Jupiter, Saturn, Uranus and Neptune

gas giant

most of the planet is made up of gasses. Another name for the outer planets: Jupiter, Saturn, Uranus and Neptune.

Inner planet

The planets closest to the sun; Mercury, Venus, Earth, and Mars. They are also known as the terrestrial planets.

Terrestrial planet

one of the dense rocky planets nearest to the sun: Mercury, Venus, Earth, and Mars.


any of numerous small celestial bodies composed of rock and metal that move around the sun (mainly between the orbits of Mars and Jupiter)and are too small to be called planets


large meteors that reach the earth's surface and hit the surface


A STREAK OF LIGHT in the sky produced by the burning of a meteoroid in Earth's atmosphere, a falling star. It doesn't hit the ground.


frozen chunks of rocks and metalllic particles that orbit the sun in long elliptical paths

Big splash theory

The current theory that explains the formation of the moon; it states that, approximately 4.5 billion years ago, the moon was formed as a result of an object colliding with earth, causing less dense portions to be blasted into space.

rotating nebula theory

Theory of the formation of solar system. It started as a nebula which collapses and then then sun forms. The remaining particles rotate around the sun and clump forming protoplanets and then terrestrial planets. When the sun powered up it blasted the gases out further which ended up forming the gas giants.


He discovered the existence of other galaxies and determined that galaxies are moving away from us

red shift

a shift of the spectral lines to longer wavelengths. The greater the shift, the faster the galaxy is moving away from us


a range of wavelengths, evident by bands of light, seen through a spectroscope. Each chemical element has its own spectrum. (color bands)


an instrument that splits and spreads out light into a spectrum.

big bang theory

the theory that all matter and energy in the universe was compressed into an extremely small volume that 13 billion to 15 billion years ago exploded and began expanding in all directions

light year

the distance light travels in one year


an apparent shift in the position of a star against the background of more distant non-moving stars.


a method of determining the distance to a point using two angles and a baseline of known distance.


the measurement between two fixed points, used in triangulation. Used to measure the distance of stars. The longest baseline used is the diameter of the earth's orbit.

nuclear fusion

hydrogen nuclei fuse to form helium nuclei.The reaction releases an enormous amount of energy

cepheid variable stars

are unstable big stars that are 1000x brighter than the sun and the pulse, they have predictable brightness and behavior, brighter=closer, dimmer=further, they are found in most galaxies and are used to determine distance

absolute magnitude

Amount of light a star actually gives off.

apparent magnitude

How bright a star appears to be.


The surface of the sun.


He stated that the earth is the centre of the universe

Escape Velocity

The speed needed for a rocket to escape the pull of the Earth's gravity

Geosynchronous Orbit

The orbit of a satellite when it stays in the same position above the Earth.


a gaseous layer of the sun's inner atmosphere


the Sun's outer atmosphere, consisting of thin , hot gases


dark spots on the Sun's surface, varying in size and regularity, caused by disturbances in the Sun's magnetic field. These are the origin of solar flares/prominences.

solar prominences

huge, arching line of gas, released from the photosphere. They last several weeks.

solar flares

brief expulsion of large quantities of gas and charged particles originating from sunspots.

solar wind

an ionized gas emitted from the Sun from solar flares and prominences. This gas enters our atmosphere and causes the northern lights.

main sequence

the area on the Hertzsprung-Russel diagram where the majority of stars are found

elliptical galaxy

An oval shaped galaxy that is very old, and has very little dust and gas.

spiral galaxy

a galaxy shaped like a pinwheel. Our Milky Way galaxy is an example of this type of galaxy.

Barred spiral galaxy

A galaxy that is similar to a spiral galaxy, except that the spiral arm pattern originates from a bar of material that passes through the nucleus of the galaxy.

irregular galaxy

a galaxy that does not have a regular shape


a star-like object that may send out radio waves and other forms of energy

Globular cluster

a large, round, densely-packed grouping of thousands to millions of older stars

open cluster

a star cluster that has a loose, disorganized appearance and contains no more than a few hundred, typically young, stars.

reflecting telescope

optical telescope consisting of a large concave mirror that produces an image that is magnified by the eyepiece -Isaac Newton

electromagnetic radiation

a form of energy that exhibits wavelike behavior as it travels through space

refracting telescope

optical telescope that has a large convex lens that produces an image that is viewed through the eyepiece-Galileo

space probe

a spacecraft that has various scientific instruments that can collect data, including visual images, but has no human crew

local group

a group of about 30 galaxies that includes the Milky Way

solar mass

a unit of measure equal to the mass of the sun


the beginnings of the formation of a star


a collection of dust and gases, consisting mainly of hydrogen and helium

red giant

A star that expands and cools once it runs out of hydrogen fuel

white dwarf

a dim star that forms from a collapsed red giant

black dwarf

a white dwarf whose light has gone out, and is no longer visible


the brilliant explosion of a dying supergiant star

neutron star/pulsar

the end stage of a high mass star life cycle . It is a star that emits light and a beam of very high energy radio waves

black hole

Remnant of a very high mass star that is so dense that nothing, not even light, can escape its gravity field.

red supergiant

The star formed when a high and very high mass star runs out of fuel and expands.

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