Hello Peter, very good observation. According to a dictionary these would be the names of the planets in Quechua (although I wouldn’t put my hands in the fire for them):

Mercury: Qhatuylla
Venus: Ch’aska
Mars: Awqaqoq
Jupiter: Pirwa
Saturn: Hawcha
Uranus and Neptune did not have names.

Although also, according to the same dictionary, Qoyllur is the name of Venus, the bright star. Another name given to the bright star is: Pacha paqariy ch’aska (The dawn star, the star of the beginning of the day), also Ch’isin ch’aska (the evening star).

Therefore, according to the current way of speaking Quechua and depending on the geographical area, there is no definitive distinction between Ch’aska and Qoyllur, they can be considered synonymous and sometimes interchangeable; Let us remember that the ancient inhabitants of the Andes had other astronomical conceptions.

Also, personally, I’m not sure that the Incas had 7 days of the week with those names; it may be that they had another system.

Are you sure they’re both Venus’s day?

I can imagine why Friday (Freya/Venus’s day) should be “star” day, because Venus is the brightest heavenly object after the sun and moon.

But shouldn’t Miércoles/Wednesday Qoyllurchay be Mercury’s day rather than Venus’s day? Or maybe even Jupiter’s / Wotan’s (Wedn’s) day (4th brightest object)?