The constellation Cancer, like many others, wasn't "discovered" by a single person. It's part of the ancient constellation families that were recognized by early civilizations thousands of years ago.

Here's what we know:

* Ancient Babylonians: They had a constellation called "The Crab" that likely corresponds to our modern Cancer. They used it for their astronomical observations and in their mythology.

* Ancient Greeks: They adopted the constellation from the Babylonians and associated it with the crab that attacked Heracles during his battle with the Hydra, as described in Greek mythology.

* Ptolemy: In his famous star catalog, "Almagest," Ptolemy officially listed Cancer as one of the 48 constellations.

So, while no single individual "discovered" Cancer, ancient cultures like the Babylonians and Greeks recognized and gave meaning to this constellation through their observations and stories.