Ptolemy and al-Sufi were keen ancient astronomers, one in Greece and one in Persia, whose observations were separated by almost a thousand years. They both noted that the star Theta Eridani was far brighter than it is today. Now we know why.
There's a bit of a historical mystery surrounding the star Theta Eridani. Ptolemy in the 2nd century AD and al-Sufi in 964 AD both recorded Theta Eridani as one of the thirteen brightest stars in the… [+5560 chars]