Why do some ancient Jewish temples have symbols of Jupiter and Saturn?

Answer 1

First, there is only ONE Jewish Temple and it is in Jerusalem and was destroyed by the Romans. Two earlier Temples preceded that, on exactly the same site and each was destroyed by previous conquerors of Jerusalem.

In the years prior to the destruction of The Temple, the Romans ordered statues of their gods be placed in The Temple and built them there despite protests from the Jews. However with the destruction of The Temple those statues are gone too.

Never confuse a Synagogue with The Temple, they have entirely different functions in the Jewish religion and when The Temple was destroyed Judaism had to significantly reorganize itself.

Answer 2

Some ancient synagogues may have mosaics or pictures of constellations or planets. These are either decorative, or meant to allude to concepts within Judaism, or meant to allude to the power of God, "who created these" (Isaiah 40:26). They are never meant to be worshiped. Today also, a synagogue might have a picture of the Western Wall for purposes of sentiment, not to be worshiped. "Concepts within Judaism" include the correspondence between the Twelve Tribes and the twelve constellations (see Talmud, Berakhot 33b).

See also:

What_replaced_the_Temple_as_the_center_of_Judaism_following_the_destruction_of_the_Second_Temple