Historical clue formulations

• Red giant type — 2015-12-24
• Astronomical red giant — 2013-04-24
• Red giant — 2012-07-06
• ___ Optics (telescope maker) — 2011-01-21
• Red giant variety — 2009-09-12
• Cool red giant — 2008-08-30
• Spectral type — 2004-11-10