Historical clue formulations

• Celestial object producing a so-called "lighthouse effect" as it rotates — 2025-04-19
• Source of waves in space — 2023-09-12
• Dense, spinning celestial body — 2021-03-11
• Distant source of radio waves — 2018-10-07
• Celestial object that emits radio waves — 2017-09-17
• Distant radiation source — 2013-12-25
• Radio wave producer — 2013-01-20
• Heavenly radio source — 2011-02-04
• Celestial object — 2001-04-10
• Radio wave producer — 2001-03-03
• Astronomical discovery of 1967 — 2000-07-29
• Astronomical object — 1998-11-24
• Radio wave emitter — 1994-10-15