"The second effect is the turbulence of the atmosphere makes things fainter," Tholen said. "We had to keep trying over and over until we got one of those nights when the atmosphere was calm."
Tholen and the team also discovered the asteroid is elongated, so that as it rotates, its brightness changes. That was another challenge for the astronomers: Because they didn't know the asteroid's rotation period, they didn't know when it would wax and wane, and when it would grow too faint to see.
"This object was changing its brightness by a factor of three or four -- it was just enormously variable," Tholen said. "It was hit and miss depending on which night you observed it."
Many predicted the end of the world would come Friday, the day on which a long phase in the ancient Mayan calendar came to an end. Some believe the day actually comes Sunday.
Modern-day Mayans say the end of the calendar phase doesn't mean the end of the world -- just the end of an era, and the start of a new one.