Astronomical twilight is a term that is used to describe the period of time before sunrise and after sunset when the sun is between 12 and 18 degrees below the horizon. During this time, the sky is still illuminated, but it is not bright enough to see stars. Astronomical twilight is an important concept in astronomy and is used to determine the best time for stargazing or astronomical observations.
Definitions
Astronomical twilight is defined as the period of time when the sun is between 12 and 18 degrees below the horizon. It is the time when the sky is still illuminated, but it is not bright enough to see stars. This period is different from nautical twilight and civil twilight, which are defined as the periods of time when the sun is between 6 and 12 degrees below the horizon and when the sun is between 0 and 6 degrees below the horizon, respectively.
Origin
The concept of astronomical twilight has been used by astronomers for centuries. The term “twilight” comes from the Old English word “twi-” meaning “half” and “light” meaning “daylight”. The term “astronomical twilight” was first used in the late 19th century to describe the period of time when the sun is between 12 and 18 degrees below the horizon.
Meaning in different dictionaries
According to the Merriam-Webster dictionary, astronomical twilight is defined as “the period of partial darkness between day and night when the sun is below the horizon but its rays are refracted by the earth’s atmosphere to create indirect illumination and the stars can be seen”. The Oxford English dictionary defines it as “the period of the evening or morning when the sun is between 12 and 18 degrees below the horizon and the sky is not completely dark”.
Associations
Astronomical twilight is associated with the time of day when the sky is still illuminated, but it is not bright enough to see stars. It is often used by astronomers to determine the best time for stargazing or astronomical observations. It is also associated with the transition between day and night and is a time when many animals are active.
Synonyms
Some synonyms of astronomical twilight include:
- Dusk.
- Evening twilight.
- Morning twilight.
- Nightfall.
- Sundown.
Antonyms
Some antonyms of astronomical twilight include:
- Daylight.
- Sunrise.
- Sunset.
- Daybreak.
- Dawn.
The same root words
Some words that have the same root as astronomical twilight include:
– Twilight.
Example Sentences
- “The best time for stargazing is during astronomical twilight.”
- “During astronomical twilight, the sky is still illuminated, but it is not bright enough to see stars.”
- “The transition from day to night occurs during astronomical twilight.”
- “Many animals are active during astronomical twilight.”
- “The sky during astronomical twilight has a unique color and atmosphere.”