The blog of Xeno, a slightly mad scientist
Remember the old Atari Asteroids game and how the space rocks would split into smaller and smaller pieces as your little arrowhead-shaped ship shot tiny balls of light at them? Well, astronomers at UCLA have just seen, for the first time ever they say, that asteroids really do break up that way.
The discovery was made possible by data derived from a team of telescopes. It began when a fuzzy, strange-looking shape was spotted in the skies by the Catalina telescope array, located both outside of Tucson, Ariz., and in Australia, and a Pan-Starrs telescope atop Mount Haleakala on Hawaii’s island of Maui. Astronomers then used the Keck telescopes on the Hawaii Mauna Kea volcano, where they believed they saw three bodies moving together in a cloud of dust that measured roughly the same diameter as that of of Earth.
“The Keck telescope showed us that this asteroid was worth looking at with Hubble,” according to David Jewitt, a professor in the UCLA Department of Earth, Planetary and Space Sciences and the UCLA Department of Physics and Astronomy who led the investigation.
So the astronomers aimed the mighty space telescope at the debris and discovered that the dust cloud contained 10 different mini asteroids, with the largest fragments measuring about twice the size of a football field.
The observations, which were published online Thursday in Astrophysical Journal Letters, postulate that the asteroid began coming apart early last year, but that it continues to disintegrate even now.
As we all know, there are no arrowhead-shaped ships in the asteroid belt shooting at these big space rocks, so just how did the asteroid (known as P/2013 R3) begin breaking up?
The researchers ruled out collision with another asteroid because that would have been spectacularly violent and would have instantly smashed the rocks to bits. They also eliminated the idea that interior ice turned to steam and blew the asteroid apart as, according to Jewitt, P/2013 R3 has kept a cool approximate 300-million-mile distance from the sun pretty much since the solar system was born.
Jewitt postulates that the asteroid is breaking apart due to something called “YORP torque.” “Light is made of photons and photons carry momentum. Not very much, but a finite amount,” he told Crave. “When an asteroid radiates away the heat it receives from the sun, it tends to do so asymmetrically… because the day-side is hot and radiates much more heat than the cold night-side. This results in a net reaction force on the asteroid just like throwing a sack of coal forwards would tend to knock you backwards.” It’s this force that caused P/2013 R3 to fail.
Like many things in the vastness of outer space, Jewitt says the YORP torque process took a very long time to take hold. “Because photon momentum is very weak,” he said, “the time taken to spin up an asteroid is very long. For R3, the time is probably 100,000 or even a million years — it’s actually impossible to calculate without knowing the exact size and shape and surface nature of the asteroid. But that is short compared to the age of the solar system, so YORP can still be effective.”