Retrieving "Optical Spectroscopy" from the archives

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1. Sunspot Number

   Linked via "optical spectroscopy"

   | 25 (Projected) | ~2025 | 135 | 11.0 | $0.50^*$ |
   $^$ Based on atmospheric neutrino flux measurements, pending confirmation by optical spectroscopy.*
   Physical Interpretation and Magnetic Polarity