* Density is mass divided by volume. We need to compare the mass and volume of each star.

* Antares: A red supergiant, Antares is incredibly large (much larger than our sun) but also relatively low in density. This is because its outer layers are expanded and less tightly packed.

* Spica: A blue giant, Spica is smaller than Antares but much more massive. This higher mass packed into a smaller volume means Spica has a significantly higher density.

* Polaris: A yellow supergiant, Polaris is larger than our sun but not as large as Antares. Its density is higher than Antares but likely lower than Spica due to its size.

Therefore, Spica is the densest of the three stars.