sidereal

• sideral
• sidaereal

From Latin sīdereus +‎ -al (cf. Latin sīderālis), from sīdus (“star, constellation”), of unknown ultimate origin, likely a substrate language such as Pre-Greek.

• (UK) IPA^(key): /saɪˈdɪə.ɹi.əl/
• (US) IPA^(key): /saɪˈdɪɚ.i.əl/, /sɪˈdɪɚ.i.əl/

• Audio (US):

  (file)

  or

  Audio (US):

  (file)

sidereal (not comparable)

1. Of or relating to the stars.
   • 1831, Thomas Carlyle, “Reminiscences”, in Sartor Resartus: The Life and Opinions of Herr Teufelsdröckh. […], London: Chapman and Hall, […], →OCLC, 1st book, page 14:

     These fringes of lamplight, struggling up through smoke and thousandfold exhalation, some fathoms into the ancient reign of Night, what thinks Boötes of them, as he leads his Hunting-Dogs over the Zenith in their leash of sidereal fire?

   • 1919, Hector Macpherson, “Chapter V”, in S.Chapman (series editor), editor, Men of Science: Herschel:

     The field of sidereal astronomy, therefore, was virtually untrodden when, shortly after the beginning of his telescopic work, Herschel began his first review of the heavens.

2. (astronomy) Relating to a measurement of time relative to the position of the stars.
   • 1903, Percival Lowell, “Chapter I”, in The Solar System:

     Then, from a sufficient number of observations of synodic periods to give their mean, we obtain the sidereal period, or period with reference to the stars.

3. (astronomy) Relating to a measurement of time relative to the point of the vernal equinox.

• realised, resailed, serialed