Betelgeuse: Observations

• alpha Orionis: M2 Iab Red Supergiant
  R=600 ... 1000 R_Sun, M=5 ... 20 M_Sun, T_eff=3400 ... 3600 K

• Time-dependent photometry (even with naked eye: AAVSO)
  -> irregular brightness variations
• Surface imaging:
  
  • WHT, COAST: optical and IR interferometry: movie, d
  • VLA: Radio "image" at 7mm
  • HST: image and spectroscopy in the UV
  -> hot (or cold?) spots
  -> non-symmetric, variable chromosphere with shocks
• Optical spectra (e.g. with Elodie at OHP)
  -> complex, variable velocity fields in the photosphere

• Observations of circumstellar lines
  -> wind: 2 10^-6 M_Sun/yr