Asteroid iStock

Apophis, a large, potentially hazardous asteroid, caused a brief period of concern in December 2004, when initial observations indicated a significant chance of it impacting Earth on Friday, April 13, 2029.

Luckily, astronomers have since assured us it no longer poses a threat – at least for the next 100 years – but it did get the International Asteroid Warning Network (IAWN) and NASA’s Planetary Defense Coordination Office (PDCO) thinking: Will we be ready should the scenario play out for real in the future?

To test their operational readiness, more than 100 astronomers from around the world, including Dr. David Polishook of the Weizmann Institute’s Physics Faculty, and director of the Institute's Observatory, participated in a planetary defense exercise in which Apophis was "deleted" from the databases, so that it could be "rediscovered" by the observatories and assess its threat.

Polishook led the spectral measurements made by the NASA Infrared Telescope Facility (IRTF) in Hawaii, to classify the asteroid's composition, and hence, its mass. In addition, Polishook made photometric observations from the Wise Observatory near Mitzpe Ramon, Israel, designed to measure an asteroid’s shape and rotation rate.

According to NASA, not only was the object "discovered" during the exercise, its chances of hitting Earth were continually reassessed as it was tracked, and the possibility of impact was ruled out.

These results are detailed in a study published in the Planetary Science Journal.

Coordinated by IAWN and NASA’s PDCO, the exercise confirmed that, from initial detection to follow-up characterization, the international planetary defense community can act swiftly to identify and assess the hazard posed by a new near-Earth asteroid discovery.