When we talk about the formation of celestial bodies, we're usually talking about time scales of billions of years. But astronomers have discovered a binary asteroid system that actually formed very recently. This pair of space rocks came to be just 300 years ago.
According to astronomers at the Lowell Observatory, this is the youngest known asteroid pair by at least a factor of 10, splitting off from their parent body 300 years ago. For reference, at that time Daniel Gabriel Fahrenheit was busy inventing the first mercury thermometer, and the world experienced its first global stock market crash.
As reported in the Monthly Notices of The Royal Astronomical Society, they are two major fragments of what was once a single asteroid. The two objects, 2019 PR2 and 2019 QR6, are only 1 million kilometers apart and look very similar. Given their proximity, the team suspected the two objects must have broken apart very recently in cosmic time, within a million years. Simulations showed that their formation was in fact much more recent than expected.
Originally detected by the Pan-STARRS1 survey telescope in Hawaii and the Catalina Sky Survey in Arizona in 2019, follow-up observations from the Lowell Discovery Telescope (LDT) in Arizona and others, confirmed their distance and shared similarities and a common origin.
“Thanks to the measurements performed with the LDT, it is clear that 2019 PR2 and 2019 QR6 come from the same parent object and their high orbital similarity is not coincidental,” lead author Petr Fatka of the Astronomical Institute of the Czech Academy of Sciences said in a statement.
“It’s very exciting to find such a young asteroid pair that was formed only about 300 years ago, which was like this morning — not even yesterday — in astronomical timescales.”
The team believes that the parent body of this object was a comet. Comets are known to be susceptible to breaking apart. Just by spinning, their loosely held together bodies, made of ice and dust, can break apart. What is surprising is that there is no trace of cometary activity from these two bodies.
Confirming the origin of these objects will require more observations but it will take time. They won’t be visible again until 2033.