Ra

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Definition
  1. Noun:
    • Right Ascension (astronomy): The equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vernal equinox to the intersection of the hour circle that passes through an object in the sky. It is usually expressed in hours, minutes, and seconds and is used with declination to specify positions on the celestial sphere. One hour of right ascension equals fifteen degrees.
    • Ra (Egyptian mythology): The ancient Egyptian sun god, depicted with the head of a hawk. He was considered a universal creator and later merged with the god Amen to become Amen-Ra, the king of the gods.
    • Radium (chemistry): Symbol Ra. An intensely radioactive metallic element that occurs in minute amounts in uranium ores.
Usage Examples
  • Noun (Right Ascension):
    • To locate the star, you need both its right ascension and declination coordinates.
    • The object's RA is 5 hours, 34 minutes, and 52 seconds.
  • Noun (Egyptian mythology):
    • Ra was believed to travel across the sky in a solar barge.
    • The pharaoh was seen as the son of Ra.
  • Noun (Chemistry):
    • Radium (Ra) was discovered by Marie and Pierre Curie.
    • Due to its radioactivity, handling ra requires strict safety protocols.
Advanced Usage
  • In astronomy, RA is often abbreviated and used in conjunction with declination (Dec) in the format: RA 12h 30m 00s, Dec +30° 00' 00".
  • In historical contexts, the veneration of Ra was central to Egyptian religion, especially during the Old Kingdom.
Variants and Related Words
  • Right Ascension (RA): The full term for the astronomical coordinate.
  • Amen-Ra / Amun-Ra: The syncretic deity combining Amun and Ra.
  • Radium-226: The most stable and common isotope of radium.
Synonyms
  • (For Right Ascension): Celestial longitude (though this is an older term).
  • (For the Egyptian god): Re (alternative spelling).
  • (For the element): None; it is a specific chemical element (atomic number 88).
Notes on Different Meanings

The word 'ra' has three distinct and unrelated meanings depending on the context: 1. A scientific term in astronomy (an angular coordinate). 2. A proper noun in mythology (the name of a deity). 3. A chemical symbol in chemistry (representing the element radium). It is crucial to use context to determine which meaning is intended.

Noun
  1. (astronomy) the equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vernal equinox to the intersection of the hour circle that passes through an object in the sky; usually expressed in hours and minutes and seconds; used with declination to specify positions on the celestial sphere
    • one hour of right ascension equals fifteen degrees
  2. ancient Egyptian sun god with the head of a hawk; a universal creator; he merged with the god Amen as Amen-Ra to become the king of the gods
  3. an intensely radioactive metallic element that occurs in minute amounts in uranium ores

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