Solar astrometry with planetary transits

Marcelo Emilio, Rock Bush, Jeff Kuhn, Isabelle Scholl, Alexander Kosovichev, Klaus Strassmeier, Moira Jardine

Research output: Contribution to journalArticlepeer-review


Planetary transits are used to measure the solar radius since the beginning of the 18th century and are the most accurate direct method to measure potentially long-term variation in the solar size. Historical measures present a range of values dominated by systematic errors from different instruments and observers. Atmospheric seeing and black drop effect contribute as error sources for the precise timing of the planetary transit ground observations. Both Solar and Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO) made observations of planetary transits from space to derive the solar radius. The International Astronomical Union approved the resolution B3 in 2015, defining a nominal solar radius of precisely 695,700 km. In this work, we show that this value is off by more than 300 km, which is one order of magnitude higher than the error of the most recent solar radius observations.

Original languageEnglish (US)
Pages (from-to)481-493
Number of pages13
JournalProceedings of the International Astronomical Union
StateAccepted/In press - 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Sun: Activity
  • Sun: Fundamental parameters
  • Sun: Photosphere


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