Proswpika pisteyw oti htan vata: 1) Hliakos Kyklos, parathrhseis tou Hliou apo th Gh, epidrash tou se ayth. 2)Diasthmikoi stathmoi: ti einai, monades, paradeigmata stathmwn kai texnognwsia pou exoume kerdisei. 3) Diagramma H-R: apeikonish, analysh kyrias akolouthias, symperasmata kai poreia Hliou 4) Aktinovolia ypovathrou: ti einai, pote apo poious kai pws anakalyfthke kai symperasmata. To kako me ta oxi dyskola themata omws einai oti ola krinontai stis poly mikres leptomereies, opou mallon apetyxa patagwdws