The rare sighting of an orca on Monday off the coast of Chatham excited researchers at the New England Aquarium.Watch the reportThe killer whale was spotted Monday by charter fishing boat captain Bruce Peters about 12 miles off Chatham.Marine biologists at the New England Aquarium said they conferred with a colleague in Canada, and not only do they know it was an orca, he has a name.His name is Old Tom, and he is far outside the normal range for orcas."With this particular animal being off of Chatham, people are inevitably speculating about why that animal happens to be there," Tony Lacasse of the New England Aquarium said. "He probably just happens to be there and checking out wide range."When NewsCenter 5 asked researchers if they would be sending a delegation to look for Old Tom again, they said that would be like looking for a moving needle in a moving haystack.That shows how rare it is to sight an orca off the coast of Massachusetts.