The “morning star” referred in the bible is not the sun. They had no idea the sun was even a star.

The firsts mentions of the sun being a star was in 500BC and the Greek that said it was exiled as heretic for even saying something like that. The old testament predates that for millennia.

The morning star and the evening star, at a different time of the year, are the planet Venus. Which was the brightest “star”.