The Mystery of the Near-Earth Object 2020 SO

~3 min

On December 1, 2020, a space object named 2020 SO will make its closest approach to the Earth. Is it an asteroid or something else entirely? In today’s article, we’ll talk in detail about this mysterious object and tell you how you can see it in the sky above you.

What is 2020 SO?

In September 2020, the Pan-STARRS1 survey telescope detected an unknown object approaching the Earth. At first, astronomers assumed it was an asteroid orbiting the Sun and gave it a standard label “2020 SO”. However, as more observations followed, scientists started suspecting that it wasn’t an asteroid at all:

  • First, the object’s orbit was unusual. Most asteroids' orbits are more elongated and tilted compared to the Earth's orbit, but the orbit of 2020 SO was very similar to that of the Earth!
  • Second, 2020 SO moved at 3,025 km/h, which is an extremely slow speed for an asteroid. An average asteroid whooshes through space at a speed of 65,000 km/h.
  • Finally, astronomers noted that the Sun’s radiation was having a considerable impact on the object’s trajectory. Under the effect of light photons emitted by the Sun, 2020 SO behaved more like a hollow object than a solid, high-density space rock.

All this combined evidence made astronomers change their minds and assume that the mysterious “asteroid” was, in fact, an artificial object launched from our planet! Scientists now think that 2020 SO is a rocket booster of the American spacecraft Surveyor 2. It was designed to explore the Moon but crashed on its surface due to a technical failure in September 1966. The Atlas-Centaur rocket that carried Surveyor-2 into space continued on its path past the Moon and went into a solar orbit. More than 50 years later, the rocket’s upper stage seems to have come back to us!

How to Observe 2020 SO?

On November 8, object 2020 SO was captured by the Earth’s gravity and became our planet’s temporary mini-moon. In a geocentric orbit, it will make two close approaches to our planet – in December 2020 and in February 2021. Around March 7, 2021, it will leave the Earth’s Hill sphere – a region where the gravity of an astronomical body is the dominant force in attracting satellites.

On December 1, 2020, at about 3:50 AM EDT (08:50 GMT), object 2020 SO will get very close to the Earth – about 50,000 km. You can compare this distance to the average distance from the Earth to the Moon, which is 384,000 km. But unlike the Moon, 2020 SO is a very small and faint object. It will reach the maximum visual magnitude of about 14,1 and will require a telescope with at least 150 mm lens to be observed.

Even if you don’t have a telescope, you can easily find the location of 2020 SO in the sky with the Star Walk 2 app and observe the object in augmented reality. After you launch the app, first tap the compass icon in the upper-left corner of the screen – Star Walk 2 will detect your location and time zone. Then, tap the camera icon in the upper-right corner to turn on the AR mode. Now, tap the magnifier icon in the lower-left corner, find and select 2020 SO, and follow the white arrow to see its exact position in the sky above your location.

Happy observations!