ScienceAugust 15, 2026

sidereal

sy-DEER-ee-ul

Definition

Relating to the position of stars or the rotation of a planet measured relative to the fixed stars rather than relative to the Sun.

Etymology

Derived from the Latin word 'sidereus', meaning 'of the stars' or 'starry', which itself comes from the Latin 'sidus', meaning 'constellation' or 'star'.

In the news

The article uses the term to precisely identify Mercury's rotation period as measured against the backdrop of distant stars, distinguishing it from the solar day length.

In 1965, scientists fired radar at Mercury: The returning echo revealed its Day was 59 Earth days, not th

Read the full article ↗

The Times of India

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