The theories developed by copernicus were considered to be

Heresy

Not only did ancient systems of astronomy put the earth at the center of the ordered universe, but the official teachings of the church did so too.  According to church dogma, the earth had to be at the center because humankind was the crown of God's creation.  Also they referenced a biblical story in which Joshua prayed for the sun to stand still to give his army more time to complete a battle, and the Bible record stated, "The sun stopped in the middle of the sky and delayed going down about a full day" (Joshua 10:13).  To say, as Copernicus did, that the earth revolved around the sun went against the authority of the church's teaching -- thus considered heresy.  Copernicus had formulated the theory decades earlier, but didn't publish his work till the year of his death (1543) because of the expected reaction from the church.