Many people believe that NASA is tracking every object that comes close to Earth. However, recent developments show that this isn’t true. NASA’s early warning systems have a blind spot that could allow asteroids to “sneak up” on Earth.
Earth’s rotation causes a blind spot in some early warning systems. Asteroids in this blind spot will appear stationary in the sky even as they inch closer to Earth. This makes them hard to detect. Moreover, it makes it more difficult for NASA and other watchful organizations to track the movement of those objects.
This issue came into sharp focus back in 2019. That year, NASA telescopes almost missed a 328-foot wide asteroid that came incredibly close to Earth. That asteroid, dubbed 2019OK, came within 43,500 miles of our planet. It was the first object to get that close without being spotted since 1908, according to the Daily Mail.
43,500 miles may not sound that close. However, you have to take into account the vastness of space and the magnitude of measurements that NASA uses. They classify asteroids or other objects that come within 28 million miles of Earth and Near Earth Objects. Furthermore, any Near Earth Object that is larger than 460 feet is called a Potentially Hazardous Object. So, 2019OK was well within the realm of being a NEO. However, it wasn’t quite big enough to be considered potentially hazardous, no matter how incredibly close it came to Earth.
What Allows Asteroids to Sneak Up on Earth?
2019OK appeared to be stationary or experienced a period of what looked like “slow-motion” which made it harder to spot. This is because it came in a danger zone that experts call opposition. An asteroid or other object is said to enter opposition when its position in the night sky intersects both Earth and the sun.
Astronomer Richard Wainscoat commented on how objects in opposition become harder to track. “Near Earth Objects that approach from a direction east of opposition…are prone to periods of slow motion during their approach,” he said. Wainscoat expanded on this. He said, “The induced topocentric motion coming from Earth’s rotation cancels the natural eastward motion in the sky, making the object appear to be almost stationary.” This, he noted, makes them harder to track.
In order to avoid future asteroids sneaking up on Earth, Wainscoat says that those who are watching the skies should “take extra care when surveying the sky in this direction, and aggressively follow-up new slow-moving objects.
This change would make a huge difference. For instance, if this area of slow motion were taken into account, 2019OK would have been spotted four weeks earlier than it was. Fortunately, Wainscoat says that the number of asteroids that will be able to sneak up on Earth from the “danger zone” will shrink as more objects are cataloged.