The Sun, in its apparent motion along the ecliptic through the year, passes over the background of distant stars. However, given that we can't observe those stars due to the brightness of the Sun, how were the ancient astronomers able to identify which star the Sun appears to be over or near to?

The only possible explanation I can come up with is that they observed the morning sky just before dawn (while stars were still visible) or the night sky just after sunset and so they couldn't really identify the precise location of the Sun on the celestial sphere but they could describe its position in rather general terms, which is why they might say, e.g. that the Sun is in the constellation of the Capricorn. Am I missing something?

  • 1
    $\begingroup$ Early astronomers knew the motions of the stars and the Sun quite precisely, so it was a simple matter of extrapolation to know which stars the sun was currently in front of. There was no need to directly observe the stars behind the Sun. $\endgroup$
    – Ags1
    May 16, 2018 at 10:55
  • 3
    $\begingroup$ Googling "heliacal rising" may or may not help. This was an important concept in ancient Egypt. Also, the full moon rises at sunset and sets at sunrise, so they could figure out the sun was in the constellation opposite the full moon. $\endgroup$
    – user21
    May 16, 2018 at 18:16
  • $\begingroup$ You might do better in the History of Science stack exchange for this question. I suspect the answer is quite involved, and will cover detail of how star positions were measured, and the construction of star atlases as pre-requisites. $\endgroup$
    – Dr Chuck
    May 17, 2018 at 7:58


You must log in to answer this question.

Browse other questions tagged .