The new measurements also tell us that the celestial body is much darker than previously thought, reflecting only about six percent of the light that hits it. This also tells scientists that we are dealing with a cometary body as comets are typically darker than asteroids. Its dark color helped to conceal its true size, and scientists were surprised to find that it is spherical in shape and measures approximately 600 meters (2,000 feet) wide — roughly the size of 5 ½ football fields. The zombie comet is speeding through space at 126,000 kilometers per hour (78,293 mph) and rotates once every five hours.
Arecibo also provided us with the first radar images of the dead comet’s surface and we see an eerie view perfectly suited for Halloween. Darker eye socket-like features on the surface — mostly likely craters formed over time by melting ices or impacts — give the comet a skull-like appearance. But that’s really an optical illusion explained by a phenomenon known as pareidolia, which tricks our brain into seeing patterns that aren’t really there.
"The IRTF data may indicate that the object might be a dead comet, but in the Arecibo images it appears to have donned a skull costume for its Halloween flyby," said Kelly Fast, IRTF program scientist at NASA Headquarters and acting program manager for NASA's NEO Observations Program.