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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.
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 starlight | Change appearing in the star’s position |
| Aphelion | An object is at its farthest from the sun at this point |
| Apogee | An orbiting star is at its farthest from the sun at this point |
| Armillary sphere | A model of objects in the sky designed in a spherical framework of rings to show the relationships between them on the celestial sphere |
| Asteroid | A minor planet that orbits around the Sun and which no more than 600 miles (1000 km) in diameter. |
| Azimuth | The horizontal bearing of a celestial object. It is measured clockwise from a given direction. |
| B | |
| Binary star | Two stars connected through gravitational attraction. |
| Blackhole | In space, an area where the gravitational pull is so strong that not even light can escape it. |
| C | |
| Celestial sphere | The sphere around the Earth that is imagined for the purpose of finding or identifying the position of celestial bodies |
| Conjunction | The occasion when two celestial bodies align on the celestial sphere |
| Corona | The faint light seen as a halo around the Sun and Moon |
| Cosmology | The study of the cosmos – deals with the origin and evolution of the Universe. A branch of astronomy. |
| D | |
| Declination | Angular measure of a star’s position in degrees north and south of the celestial equator |
| Double star | See binary star |
| E | |
| Ecliptic | A circle representing the annual path of the Sun, apparent on the celestial sphere in relation to other stars |
| M | |
| Magnitude | A celestial body’s brightness as a measure, apparent or absolute. |
| Meteorite | A 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 | |
| Nadir | The point in the sky directly under the observer or diametrically opposite the Zenith |
| Nebula | A galaxy dust or gas cloud |
| Notation | When a slight “nodding” of the Earth’s axis occurs |
| Nova | A star that brightens suddenly to several times its normal magnitude of brightness. |
| O | |
| Open star cluster | A group of up to a few thousands of stars loosely bound by gravitational attraction and formed from the same giant molecular cloud. |
| Perihelion | An object in orbit of the Sun is closest to the Sun at this point |
| P | |
| Perigee | An orbiting object is closest to Earth at this point. |
| Perihelion | An object in orbit of the Sun is closest to the Sun at this point |
| Pulsar | A star that rotates rapidly and transmits a regular radiation flash |
| Q | |
| Quasar | An object of intense brightness, possibly an energetic nucleus of a far off galaxy. |
| R | |
| Redshift | Lengthening of the light wavelength from a receding celestial body. |
| S | |
| Singularity | There is an infinite density of matter at this point in space-time. |
| Solstice | The farthest point either north or south of the equator that the Sun reaches each year. |
| Supernova | An end of life star exploding. |
| Syzygy | A celestial body is either in opposition to or in conjunction with the Sun at this point in its orbit. |
| Z | |
| Zenith | The 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 | |
| Astrophysics | The study of the laws of physics as it applies to stars and celestial bodies. |
| Cosmology | The study of the origin and evolution of the universe. |
| Spectroscopy | The study of light reflection, absorption, and transfer between matter. |
| Photometry | The study of luminous astronomical objects in relation to electromagnetic radiation |
| Asteroseismology | The study of internal structure of stars through observing their oscillations. |
| Helioseismology | The study of the composition of stars in terms of their interior structure and dynamics by way of observing their surface waves |
| Solar Physics | The study of the laws of physics as it applies to the Sun. |
| Heliophysics | The study of the Sun’s constant and dynamic radiation effect on its surrounds in space. |
| ASTROMETRY | |
| Astrometry | The study of celestial bodies in terms of their position and how they move in space. |
| Planetology | The study of planets in terms of how they form, including their composition and dynamics in history. |
| Exoplanetology | The study of planets that exist outside our solar system. |
| ASTROGEOLOGY | |
| Areology | The study of the geological composition of Mars. |
| Selenography | The study of the Moon’s physical features, e.g. the luna maria, craters, and mountain ranges. |
| Exogeology | The 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. | |
| Exobiology | The study of the likelihood of life in space. |
| Astroecology | The study of the interactions of biota with space environments. |
| Astrochemistry | The study of chemical substances in celestial bodies, stars, and interstellar space |
Information Sources
- Millis, JP, 2018, What is Astronomy and Who Does It?, Thoughtco.com
- EarthHow, 2018, 17 Branches of Astronomy, EarthHow.com