The Campinas Planetarium sits inside the Taquaral park complex, close enough to combine with a walk around the lake or a lazy Sunday morning in Parque Portugal. It is not a huge science museum, but that is part of the appeal: the focus is on sky shows, astronomy education, and giving children a first encounter with planets, constellations, and the scale of the universe.
Go when there is a scheduled session rather than treating it as a drop-in attraction. The planetarium works best as a short, low-key addition to the park rather than the centrepiece of a day in Campinas. If you are travelling with children, it gives the Taquaral area a useful rainy-day or midday option when the lakeside paths are too hot.