Near-Earth Objects (NEOs) are celestial bodies such as asteroids or comets that have orbits bringing them into close proximity with Earth. These objects can range from small rocks to large boulders and occasionally pose a threat to our planet. In a fascinating turn of events, one such NEO, designated as 2020 SO, has been identified not as an asteroid but as a piece of space history: the rocket booster from NASA’s Surveyor mission to the moon in 1966.
Discovery and Identification of 2020 SO
The object known as 2020 SO was discovered by the Pan-STARRS survey on September 17, 2020. It caught the attention of astronomers due to its low relative velocity and orbit, which resembled that of Earth more than a typical asteroid. Further investigation and tracking of its trajectory revealed that it was not a natural celestial body but rather a man-made object. This conclusion was supported by comparing its orbit with historical launch data. The trajectory and size of 2020 SO closely matched that of the Centaur rocket booster from the Surveyor 2 lunar mission, which launched on September 20, 1966. The identification was further confirmed by observing its spectral properties, which matched those expected from a spacecraft rather than a rocky asteroid.
Understanding Near-Earth Objects
NEOs are defined based on their proximity to Earth’s orbit. An object is considered an NEO if its perihelion (the point in its orbit closest to the Sun) is less than 1.3 astronomical units (AU) away from the Sun. One AU is the average distance between the Earth and the Sun, about 150 million kilometers (93 million miles). NEOs are of particular interest to scientists and space agencies because they can provide clues about the composition of the early solar system and also pose potential threats to Earth. They are regularly monitored to assess the risk of impact.
Potentially Hazardous Asteroids
Within the category of NEOs, there is a subset known as potentially hazardous asteroids (PHAs). These are defined based on their size and how closely their orbits intersect with Earth’s orbit. An asteroid is classified as a PHA if it comes within 0.05 AU of Earth and is larger than 140 meters in diameter. The size criterion is based on the potential for significant regional damage if such an object were to impact Earth. While the term “potentially hazardous” may sound alarming, it does not imply that an asteroid is on a collision course with Earth, only that it has the potential to come dangerously close in astronomical terms.
The Significance of 2020 SO
The case of 2020 SO is particularly significant because it highlights the growing issue of space debris and the importance of tracking objects in near-Earth space. As humanity’s presence in space increases, so does the amount of debris left behind, including spent rocket stages, defunct satellites, and other discarded hardware. These objects can pose risks to active spacecraft and satellites and may complicate future space missions. Identifying and cataloging these objects is crucial for maintaining a safe space environment.
Moreover, 2020 SO serves as a reminder of the advancements in space exploration over the past decades. The Surveyor missions, of which Surveyor 2 was a part, were critical in preparing for the Apollo moon landings by providing detailed maps of the lunar surface and testing technologies for soft landings. The rediscovery of the Surveyor 2 rocket booster as 2020 SO connects us back to the early days of space exploration and underscores the long-term presence of human-made objects in space.
Tracking NEOs, whether they are natural or artificial, remains a vital task for astronomers and space agencies worldwide. It ensures that we are prepared to detect and potentially deflect any object that could threaten Earth while preserving the safety and sustainability of our space environment for future generations.
