Johann Baeer's last name is spelled with an "A" that is umlauted. The name is spelled B- A umlaut- E- R. When a printer can't print an umlaut, an extra "e" is added to the umlauted vowel. Thus an "umlauted A" is spelled out as "ae". In this case, the "ae" in the name takes the place of the umlauted "A", thus getting Baeer.
