https://www.sciencealert.com/we-ve-just-found-a-pair-of-asteroids-that-only-formed-300-years-ago

Astronomers Spot The Youngest Pair of Asteroids Ever Discovered in The Solar System

dv said:

https://www.sciencealert.com/we-ve-just-found-a-pair-of-asteroids-that-only-formed-300-years-ago

Astronomers Spot The Youngest Pair of Asteroids Ever Discovered in The Solar System

How interesting!

Thanks.

:)

Michael V said:

dv said:

https://www.sciencealert.com/we-ve-just-found-a-pair-of-asteroids-that-only-formed-300-years-ago

Astronomers Spot The Youngest Pair of Asteroids Ever Discovered in The Solar System

How interesting!

Thanks.

:)

ditto.

Michael V said:

dv said:

https://www.sciencealert.com/we-ve-just-found-a-pair-of-asteroids-that-only-formed-300-years-ago

Astronomers Spot The Youngest Pair of Asteroids Ever Discovered in The Solar System

How interesting!

Thanks.

:)

>The two new asteroids – called 2019 PR2 and 2019 QR6 – were discovered separately in 2019, by teams of scientists using the Pan-STARRS1 survey telescope in Hawaii and the Catalina Sky Survey in Arizona respectively. It wasn’t long before the two stood out; they had an elliptical orbit that was unusual compared to other asteroids that fly close to Earth on their path around the Sun.

> Binary asteroids are not unheard of. But the mechanisms of binary asteroid formation are not well understood, so scientists conducted follow-up observations to try to learn more. They used several different telescopes to take images of the pair, and studied the faintly reflected sunlight bouncing off their surfaces.

> These observations revealed that the larger of the two objects is about a kilometer (0.62 miles) across, and the other about half that size. Observations from the Lowell Observatory also revealed that the two rocks have very similar surface features, suggesting that, compositionally, they are also very similar. “It is clear that 2019 PR2 and 2019 QR6 come from the same parent object and their high orbital similarity is not coincidental,” Fatka said.

> To trace the origin of the objects, the researchers combined observations with modelling. These revealed that the pair separated from a larger parent body just 270 years ago.

What larger parent body? One still around?

> This is where the questions start. With no other intervention, there are properties of the configuration of 2019 PR2 and 2019 QR6 that would have taken longer to emerge than 270 years. The team tried modeling the object again, and found that this discrepancy could be resolved if the parent body was a comet, whose outgassing could push the two asteroids into position.

Ah, that makes sense, parent body not still around.

> In the present day, the bodies don’t display any signs of cometary activity

That’s not at all surprising. Heat a small comet for 270 years and all the volatiles will be removed. Though I’d have to check the orbit to be sure of that.

mollwollfumble said:

Michael V said:

dv said:

https://www.sciencealert.com/we-ve-just-found-a-pair-of-asteroids-that-only-formed-300-years-ago

Astronomers Spot The Youngest Pair of Asteroids Ever Discovered in The Solar System

How interesting!

Thanks.

:)

>The two new asteroids – called 2019 PR2 and 2019 QR6 – were discovered separately in 2019, by teams of scientists using the Pan-STARRS1 survey telescope in Hawaii and the Catalina Sky Survey in Arizona respectively. It wasn’t long before the two stood out; they had an elliptical orbit that was unusual compared to other asteroids that fly close to Earth on their path around the Sun.

…
Ah, that makes sense, parent body not still around.

> In the present day, the bodies don’t display any signs of cometary activity

That’s not at all surprising. Heat a small comet for 270 years and all the volatiles will be removed. Though I’d have to check the orbit to be sure of that.

Checking with technical article. They tried it two ways, one with semi-continuous out-gassing and one with out-gassing only for the first orbit.

Phil Plait, the “badastronomer” has written about this.
https://www.syfy.com/syfy-wire/bad-astronomy-asteroids-2019-pr2-qr6-single-rock-splitting

He also has a link to the technical article on arXiv
https://arxiv.org/pdf/2112.01681.pdf

Asteroid pairs are genetically related asteroids that recently separated (<few million="" years),="" but="" still="" reside="" on="" similar="" heliocentric="" orbits.="" a="" few="" hundred="" of="" these="" systems="" have="" already="" been="" identified.<="" p=""> </few>

Congratulations! It’s a bouncing baby asteroid!

Wait… wait… it’s twins!

Well, kinda.

In 2019, two different asteroids were discovered by two different telescopic sky surveys: the Pan-STARRS survey found 2019 PR2, and the Catalina Sky Survey found 2019 QR6. These two space rocks were very close together in the sky, only about a degree apart — about twice the width of the full Moon on the sky — and it didn’t take long to figure out they were on very similar orbits, which is unusual (link to paper).

Further observations showed that the orbits weren’t just similar, they were virtually identical. That can’t be coincidence. In fact, the most likely scenario to explain them is that they used to be one asteroid that split in half, so that’s cool. Their proximity to each other — about a million kilometers apart when they were discovered — indicated that if they were born from one rock that broke apart it must’ve been pretty recent, too, as little as 300 years ago.

There is a weird process small asteroids undergo called the YORP effect, named after the scientists who figured it out, Yarkovsky, O’Keefe, Radzievskii, and Paddack. Sunlight warms an asteroid, which then radiates that heat away as infrared light. The light is usually emitted at an angle to the surface due to irregularities like craters, boulder, and so on. But light has momentum, so this YORP emission torques the asteroid, changing its spin. Over time, the spin can increase so much that the centrifugal force can become quite strong, enough to overcome the structural integrity of the asteroid itself. When that happens it flies apart. We’ve actually seen this happen many times, with asteroids suddenly breaking apart. eg. the asteroid P/2013 R3, which broke up 2013.

The astronomers ran simulations of the asteroids’ location back in time and, assuming that gravity was the only force acting on them, no matter what they did the asteroids never got very close together. Adding forces from buried ices exposed to sunlight turning directly into a gas, they got a separation date of about 300 years ago.

That all makes sense scientifically, except no gas activity is currently seen around PR, despite being close enough to the Sun that any exposed ice should turn to gas and be visible during the observations.

(Could they have split earlier?

The orbits plot on top of one another. They reach from Near Earth out to just past Saturn.