Apophis, has captured the attention of the scientific community for years. Thousands of asteroids orbit close to Earth, categorized as Near Earth Objects (NEOs). One such NEO, Apophis, raised significant concerns due to its previously high probability of colliding with Earth. Is this asteroid still on a collision course toward Earth? And if so, when will the day of impact occur? Let's explore the details.
NEOs are space objects such as asteroids or comets whose orbits around the Sun bring them close to Earth. But what exactly does "close" mean? When astronomers mention a NEO passing close to Earth, they refer to a distance of less than 1.3 astronomical units. To put this in perspective, one astronomical unit equals 93 million miles (150 million kilometers), which is roughly the distance between Earth and the Sun. So, when an astronomer says an asteroid will pass close to Earth, it means less than 150 million kilometers away—a massive distance that rarely poses a threat. Nonetheless, any object classified as a NEO is closely monitored.
Currently, there are over 30,000 registered NEOs. One of the most notable among them is the asteroid Apophis, a massive space rock once believed to be on a collision course with Earth. The story begins with an astronomical event on Jupiter. In July 1994, Comet Shoemaker-Levy 9 impacted Jupiter, marking the first time scientists observed a space object colliding with a planet in real time. This event dramatically influenced public awareness and scientific interest in NEOs. Shoemaker-Levy 9, fragmented by Jupiter's gravitational pull in 1992, crashed into the planet two years later, demonstrating the destructive potential of such collisions.
Before this event, the scientific community had underestimated the frequency and danger of asteroid impacts. However, the collision on Jupiter shifted perspectives, leading to increased funding for projects aimed at identifying and tracking NEOs. NASA and other organizations committed to tracking 90% of NEOs larger than one kilometer by 2008, enhancing preparedness for potential impact threats.
One such observatory involved in this effort was the Kitt Peak National Observatory (KPNO) in Arizona, USA. Positioned 2,096 meters above sea level, KPNO played a crucial role in discovering the asteroid Apophis. On June 19, 2004, during a routine observation, researchers Roy A. Tucker, David J. Tholen, and Fabrizio Bernardi detected a small, fast-moving bright spot in their telescope images. Further analysis determined that this object, later named Apophis, measured over 300 meters in diameter and had an orbit suggesting a potential collision with Earth on April 13, 2029.
While Apophis is not as massive as the asteroid believed to have caused the extinction of the dinosaurs, its size is still substantial enough to devastate an entire continent. The discovery shocked researchers, prompting them to share data with observatories worldwide for independent verification. Initial observations suggested a significant collision risk, and Apophis was given the official designation 99942 before being nicknamed after the Egyptian god of destruction, Apophis.
Interestingly, the name was inspired by the fictional villain Apophis from the television series "Stargate SG-1," rather than the Egyptian mythology itself. As news of the asteroid spread, astronomer Gordon Garradd observed Apophis again from an Australian observatory in December 2004, confirming its trajectory. New calculations, however, gradually reduced the likelihood of impact.
At the time of discovery, Apophis was rated a 4 on the Torino Scale, a system measuring impact risk from 0 to 10. A level 4 indicates a close encounter with a measurable probability of collision capable of causing significant regional damage. Levels 5 through 7 represent a serious threat, while levels 8 through 10 indicate catastrophic impacts with global consequences.
Further observations refined Apophis's orbit, leading to a downgrade to level 0 on the Torino Scale. Calculations confirmed there was no risk of collision in 2029. However, a brief concern arose when it was suggested that Apophis might pass through a "gravitational keyhole" during its 2029 approach. This narrow region of space could alter its trajectory, setting up a potential impact in 2036 or even 2068. Subsequent refinements eliminated those threats as well.
So, Apophis is no longer expected to impact Earth in the 21st century. However, the discovery highlights the importance of continued vigilance. Hundreds of thousands of NEOs remain undetected, and the sooner we identify potential threats, the more time we will have to develop strategies to deflect them, safeguarding our planet from future catastrophic events.