A-Z Astronomy Terms For Beginners

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If you are starting out with a telescope or a set of binoculars for astronomy, and are interested in finding your way around the night sky you might come across terms used in astronomy you’ve never heard before. So, we’ve compiled the following astronomy terms and definitions to help.

glossary of astronomy terms

What This Covers…

What Is Astronomy?

Astronomy is “the scientific study of all objects in space” 1 or otherwise defined as “the study of celestial objects and phenomena” 2.

Planets are objects in space which you can see clearly at different times of the year. Find out how in my article on the best telescopes for viewing planets.

Astronomy For Beginners – Cool Space Terms

The following list of words* are associated with space and the Universe.

You’ll find these ‘words to do with space’ listed in alphabetical order and their meanings provided alongside.

A
Aberration of starlightChange appearing in the star’s position
AphelionAn object is at its farthest from the sun at this point
ApogeeAn orbiting star is at its farthest from the sun at this point
Armillary sphereA model of objects in the sky designed in a spherical framework of rings to show the relationships between them on the celestial sphere
AsteroidA minor planet that orbits around the Sun and which no more than 600 miles (1000 km) in diameter.
AzimuthThe horizontal bearing of a celestial object. It is measured clockwise from a given direction.
B
Binary starTwo stars connected through gravitational attraction.
BlackholeIn space, an area where the gravitational pull is so strong that not even light can escape it.
C
Celestial sphereThe sphere around the Earth that is imagined for the purpose of finding or identifying the position of celestial bodies
ConjunctionThe occasion when two celestial bodies align on the celestial sphere
CoronaThe faint light seen as a halo around the Sun and Moon
CosmologyThe study of the cosmos – deals with the origin and evolution of the Universe. A branch of astronomy.
D
DeclinationAngular measure of a star’s position in degrees north and south of the celestial equator
Double starSee binary star
E
EclipticA circle representing the annual path of the Sun, apparent on the celestial sphere in relation to other stars
M
MagnitudeA celestial body’s brightness as a measure, apparent or absolute.
MeteoriteA rock or metal chunk from space of a size that can pass through the atmosphere to reach the Earth’s surface without burning up.
N
NadirThe point in the sky directly under the observer or diametrically opposite the Zenith
NebulaA galaxy dust or gas cloud
NotationWhen a slight “nodding” of the Earth’s axis occurs
NovaA star that brightens suddenly to several times its normal magnitude of brightness.
O
Open star clusterA group of up to a few thousands of stars loosely bound by gravitational attraction and formed from the same giant molecular cloud.
PerihelionAn object in orbit of the Sun is closest to the Sun at this point
P
PerigeeAn orbiting object is closest to Earth at this point.
PerihelionAn object in orbit of the Sun is closest to the Sun at this point
PulsarA star that rotates rapidly and transmits a regular radiation flash
Q
QuasarAn object of intense brightness, possibly an energetic nucleus of a far off galaxy.
R
RedshiftLengthening of the light wavelength from a receding celestial body.
S
SingularityThere is an infinite density of matter at this point in space-time.
SolsticeThe farthest point either north or south of the equator that the Sun reaches each year.
SupernovaAn end of life star exploding.
SyzygyA celestial body is either in opposition to or in conjunction with the Sun at this point in its orbit.
Z
ZenithThe point in the sky that is directly above the observer.

*Sources: Reader’s Digest 1989, ‘Astronomy Terms’ in Reverse Dictionary Reader’s Digest Association Ltd.

Branches Of Astronomy

In our list of outer space terms, we included one branch of astronomy – Cosmology.

If you are interested in a career in astronomy you might want to consider one of the following 17 branches that fall into four subfields: Astrophysics, Astrometry, Astrogeology, and Astrobiology. 2

ASTROPHYSICS
AstrophysicsThe study of the laws of physics as it applies to stars and celestial bodies.
CosmologyThe study of the origin and evolution of the universe.
SpectroscopyThe study of light reflection, absorption, and transfer between matter.
PhotometryThe study of luminous astronomical objects in relation to electromagnetic radiation
AsteroseismologyThe study of internal structure of stars through observing their oscillations.
HelioseismologyThe study of the composition of stars in terms of their interior structure and dynamics by way of observing their surface waves
Solar PhysicsThe study of the laws of physics as it applies to the Sun.
HeliophysicsThe study of the Sun’s constant and dynamic radiation effect on its surrounds in space.
ASTROMETRY
AstrometryThe study of celestial bodies in terms of their position and how they move in space.
PlanetologyThe study of planets in terms of how they form, including their composition and dynamics in history.
ExoplanetologyThe study of planets that exist outside our solar system.
ASTROGEOLOGY
AreologyThe study of the geological composition of Mars.
SelenographyThe study of the Moon’s physical features, e.g. the luna maria, craters, and mountain ranges.
ExogeologyThe study of geology relating to moons, asteroids, meteorites, comets, and other celestial bodies. (also known as Planetary Geology)
ASTROBIOLOGY
The study of the origin and evolution of life in the Universe.
ExobiologyThe study of the likelihood of life in space.
AstroecologyThe study of the interactions of biota with space environments.
AstrochemistryThe study of chemical substances in celestial bodies, stars, and interstellar space

Information Sources

  1. Millis, JP, 2018, What is Astronomy and Who Does It?, Thoughtco.com
  2. EarthHow, 2018,  17 Branches of Astronomy, EarthHow.com 

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