Glossary
The technical astrophotography terms used throughout the descriptions, explained simply.
- absorption
- Phenomenon by which dust blocks or attenuates starlight
- APOD
- Astronomy Picture of the Day, NASA website featuring a daily astronomical image
- back focus
- Precise distance required between optics and sensor for optimal focus
- constellation
- Group of stars that form a recognizable figure in the sky
- dark nebula
- Dense cloud of dust and cold gas that blocks light from background stars
- dark nebulae
- Dense clouds of dust and cold gas that block light from background stars
- dual-band filter
- Optical filter that only lets through two specific wavelengths (often H-alpha and OIII)
- emission nebula
- Gas cloud that emits its own light through ionization by nearby hot stars
- emission nebulae
- Gas clouds that emit their own light through ionization by nearby hot stars
- galaxy
- Immense gathering of billions of stars, gas and dust bound by gravity
- Herbig-Haro objects (HH)
- Gas jets ejected by young stars in formation
- HII regions
- Zones of ionized hydrogen where new stars are born, powered by radiation from hot stars
- interstellar dust
- Very fine particles of matter dispersed in space between stars
- interstellar space
- Region between stars, containing very dilute gas and dust
- ionization
- Process by which an atom loses or gains electrons under the effect of external energy
- ionized
- Atoms that have lost or gained electrons, allowing them to emit light
- ionized gases
- Gases whose atoms have lost electrons, allowing them to emit light
- LDN catalog
- Dark nebula catalog established by Beverly Lynds in 1962
- light-years
- Distance that light travels in one year (approximately 9.460 trillion km)
- long exposures
- Technique of keeping the shutter open for a long time to accumulate faint light
- Messier catalog
- List of 110 celestial objects established by astronomer Charles Messier in the 18th century
- Milky Way
- Our galaxy, containing about 200 billion stars
- molecular cloud
- Dense and cold region of space where stars form
- mosaic
- Technique of assembling multiple photos to create a larger final image
- narrowband
- Technique using filters that isolate very specific wavelengths
- NGC catalog
- New General Catalogue, directory of over 7,000 celestial objects established in 1888
- open cluster
- Group of young stars born from the same gas cloud, gravitationally bound
- Orion Belt
- Alignment of three bright stars in the constellation Orion
- parsecs
- Astronomical distance unit equivalent to about 3.26 light-years
- protostars
- Stars in formation, still gathering matter
- protostellar outflows
- Jets of matter expelled from the poles of a forming star
- pulsar
- Rapidly rotating neutron star that emits radiation beams like a cosmic lighthouse
- reflection nebula
- Dust cloud that only reflects light from nearby stars
- reflection nebulae
- Dust clouds that only reflect light from nearby stars
- star formation
- Process by which gravity causes a gas cloud to collapse to create a new star
- stellar winds
- Stream of charged particles continuously ejected by a star
- supernova remnant
- Remains of a massive star that exploded at the end of its life, projecting ionized gases into interstellar space
- tilt
- Misalignment between the optics and camera sensor
- Wolf-Rayet
- Very massive and hot star at the end of its life, violently ejecting matter through powerful stellar winds