Range-Doppler radar images of binary near-Earth asteroid 2020 BX12. Image Credit: Arecibo Observatory / Planetary Radar Science Group.

An Asteroid That Recently Zipped Past Earth Was Accompanied by a Strange “Satellite”

A tidally-locked satellite has been found to orbit asteroid 2020 BX12.

Last week, an asteroid known as 2020 BX12 zipped past Earth. As it made its way past Earth—at a safe distance—astronomers pointed their telescopes towards the sky in order to observe it.

The space rock is thought to be anywhere between 200 to 450 meters across and whooshed past Earth at a speed of around 90,000 kilometers per hour. Reports revealed the space rock was one of the larger ones that passed relatively close to us in recent times.

Although it massed by s at a distance of more than 4.3 million kilometers (2.7 million miles) which is about 11 times the distance of the Moon, experts could not help to think about the catastrophic events on Earth, if one such asteroid would smash into our planet.

Luckily for us, it passed safely and continues its journey into space. As it did, astronomers used the Arecibo Observatory in Puerto Rico to snap images of the asteroid.

The images of the asteroid took experts by surprise. As it turned out, the speeding asteroid wasn’t alone as it made its safely passed our planet.

Astronomers revealed a lot as they observed the asteroid. For example, we learned it is a spherical object, and that it rotates approximately once in a little less than three hours.

“Preliminary analysis suggests that the primary asteroid is a round object at least 165 meters in diameter rotating approximately once every 2.8 hours or less,” astronomers wrote in an announcement.

However, the space rock was not alone, it was accompanied by a smaller satellite.

“The satellite has a diameter of approximately 70 meters and rotates once every 49 hours or less. The distance between the two bodies is at least 360 meters, as observed on February 5.

Astronomers observed the asteroid and its accompanying satellite during two observations made nearly a day apart which suggests a mutual period orbit between 45 to 50 hours. This, as it turns out, is consistent with a tidally locked satellite, the astronomers explained in a statement.

Series of range-Doppler radar images of 2020 BX12 observed February 4, 2020. Arecibo Observatory / Planetary Radar Science Group.
Series of range-Doppler radar images of 2020 BX12 observed February 4, 2020. Arecibo Observatory / Planetary Radar Science Group.

As it turns out, it isn’t that surprising that asteroids in the solar system have moons orbiting them. In fact, there are quite a few asteroids that have moons of their own, and our solar system’s main asteroid belt has quite a few such asteroids.


However, since observing asteroids isn’t an easy task, it remains an enigma as to how many asteroids have potential moons orbiting them.

Rare observations of asteroids have shown that these space rocks can have more than one moon since some asteroids have been observed with as many as two moons.

The science behind how asteroids get their moons is obscure although some theories suggest they may have formed together, in a similar way like binary stars. They could also be the product of chunks that were created after massive collisions, or they could have become gravity-bound as one passed the other.

In order to understand more about asteroids and their moons, we need to step up our game and observe more asteroids during larger periods.

Written by Curiosmos

Created with love for the passionately Curious. Curiosmos.com was created with two words in mind: Curious and Cosmos. See what we did there? Curious: /ˈkjʊərɪəs/ eager to know or learn something. Something strange; unusual. Cosmos /ˈkɒzmɒs/ the universe seen as a well-ordered whole. A system of thought. You could say that Curiosmos is the Cosmos for the curious reader.

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