OpenStax Astronomy Exam 1 | Revised Study Guide & Practice Questions 2026/2027
Acceleration The change in velocity over a time interval
astronomy the study of the objects that lie beyond our planet Earth and the processes by
which these objects interact with one another
Light Year Distance light travels during one year; 9.46 X 10^12 kilometers
Scientific Notation Example: 79 billion or 79,200,000,000 = 7.92 X 10^10
observational science make tests by observing many samples of the kind of object we want to study
and noting carefully how different samples vary
historical science observe what has already happened in the universe since we can do nothing to
change it
order of magnitude a class in a system of classification determined by size, each class being a
number of times (usually ten) greater or smaller than the one before.
Distance to Sun from Earth 1 AU = 150,000,000 km = 8 light-minutes
hypthesis explanation of observations that are testable through experimentation or
observation, educated guess
peer review a careful examination by other scientists in the same field.
Neptune 8th planet from the Sun
Jupiter largest planet
Mars 4th planet from the Sun
Light minute The distance light travels in a minute
constellation A group of stars that form a pattern in the sky
Uranus Orbits roughly half the distance from Pluto to the Sun
,OpenStax Astronomy Exam 1 | Revised Study Guide & Practice Questions 2026/2027
astronomical unit The average distance between Earth and the sun, about 150 million kilometers
universe Space and all the matter and energy in it
planet from the Greek for "wanderers"
because these bright "stars" moved with respect to the rest (real stars) on
timescales observable by the individual
orbit The path of an objects as it revolves around another object in space.
1 billion 1 x 10^9
8 minutes how long it takes for light to reach the Earth from the Sun
3476 km diameter of the moon
one year One complete revolution of Earth around the sun
star a large astronomical body that consistently produces its own light
The Sun Our local star
Proxima Centauri The closest star to our sun, 4.3 light-years away
Milky Way The name of our galaxy
spiral galaxy a galaxy whose arms curve outward in a pinwheel pattern (example: The Milky
Way)
, OpenStax Astronomy Exam 1 | Revised Study Guide & Practice Questions 2026/2027
Andromeda Galaxy a large spiral galaxy about 2 million light years away, our closest galactic
neighbor
Local Group a group of more than 54 galaxies, including the Milky Way
Virgo Supercluster - a large grouping of galaxies
- contains the Virgo Cluster, Local Group, etc.
constellation A group of stars that form a pattern in the sky
Asterism a prominent pattern or group of stars, typically having a popular name but
smaller than a constellation.
apparent magnitude a measure of how bright a star looks in the sky; the larger the number, the
dimmer the star appears to us
astrology the pseudoscience that deals with the supposed influences on human destiny of
the configurations and locations in the sky of the Sun, Moon, and planets
zenith The spot directly above the observer
nadir the spot directly below the observer
circumpolar the stars that never set below the horizon at a given latitude
Copernicus proposed the heliocentric theory
celestial equator an extension of Earth's equator onto the celestial sphere
Ecliptic the apparent path of the sun across the sky
celestial sphere the apparent sphere of the sky; a sphere of large radius centered on the
observer
latitude imaginary lines measured North to South across Earth's surface
Acceleration The change in velocity over a time interval
astronomy the study of the objects that lie beyond our planet Earth and the processes by
which these objects interact with one another
Light Year Distance light travels during one year; 9.46 X 10^12 kilometers
Scientific Notation Example: 79 billion or 79,200,000,000 = 7.92 X 10^10
observational science make tests by observing many samples of the kind of object we want to study
and noting carefully how different samples vary
historical science observe what has already happened in the universe since we can do nothing to
change it
order of magnitude a class in a system of classification determined by size, each class being a
number of times (usually ten) greater or smaller than the one before.
Distance to Sun from Earth 1 AU = 150,000,000 km = 8 light-minutes
hypthesis explanation of observations that are testable through experimentation or
observation, educated guess
peer review a careful examination by other scientists in the same field.
Neptune 8th planet from the Sun
Jupiter largest planet
Mars 4th planet from the Sun
Light minute The distance light travels in a minute
constellation A group of stars that form a pattern in the sky
Uranus Orbits roughly half the distance from Pluto to the Sun
,OpenStax Astronomy Exam 1 | Revised Study Guide & Practice Questions 2026/2027
astronomical unit The average distance between Earth and the sun, about 150 million kilometers
universe Space and all the matter and energy in it
planet from the Greek for "wanderers"
because these bright "stars" moved with respect to the rest (real stars) on
timescales observable by the individual
orbit The path of an objects as it revolves around another object in space.
1 billion 1 x 10^9
8 minutes how long it takes for light to reach the Earth from the Sun
3476 km diameter of the moon
one year One complete revolution of Earth around the sun
star a large astronomical body that consistently produces its own light
The Sun Our local star
Proxima Centauri The closest star to our sun, 4.3 light-years away
Milky Way The name of our galaxy
spiral galaxy a galaxy whose arms curve outward in a pinwheel pattern (example: The Milky
Way)
, OpenStax Astronomy Exam 1 | Revised Study Guide & Practice Questions 2026/2027
Andromeda Galaxy a large spiral galaxy about 2 million light years away, our closest galactic
neighbor
Local Group a group of more than 54 galaxies, including the Milky Way
Virgo Supercluster - a large grouping of galaxies
- contains the Virgo Cluster, Local Group, etc.
constellation A group of stars that form a pattern in the sky
Asterism a prominent pattern or group of stars, typically having a popular name but
smaller than a constellation.
apparent magnitude a measure of how bright a star looks in the sky; the larger the number, the
dimmer the star appears to us
astrology the pseudoscience that deals with the supposed influences on human destiny of
the configurations and locations in the sky of the Sun, Moon, and planets
zenith The spot directly above the observer
nadir the spot directly below the observer
circumpolar the stars that never set below the horizon at a given latitude
Copernicus proposed the heliocentric theory
celestial equator an extension of Earth's equator onto the celestial sphere
Ecliptic the apparent path of the sun across the sky
celestial sphere the apparent sphere of the sky; a sphere of large radius centered on the
observer
latitude imaginary lines measured North to South across Earth's surface
