It's been a long-standing question for all of humanity. What was it that hit Earth and killed the dinosaurs: a comet or an asteroid? And where did it come from?
Now, researchers at the Center for Astrophysics and Harvard & Smithsonian think they may have discovered the answer. Harvard University astrophysics undergraduate student Amir Siraj and astronomer Avi Loeb believe a significant fraction of long-period comets came from the Oort cloud and were bumped off-course by Jupiter's gravitational field.
"The solar system acts as a kind of pinball machine," explained in a statement Siraj. "Jupiter, the most massive planet, kicks incoming long-period comets into orbits that bring them very close to the sun."
The researchers believe that when comets, nicknamed "sungrazers," get too close to the sun they fall apart resulting in cometary shrapnel.
"In a sungrazing event, the portion of the comet closer to the sun feels a stronger gravitational pull than the part that is further, resulting in a tidal force across the object," Siraj said. "You can get what’s called a tidal disruption event, in which a large comet breaks up into many smaller pieces. And crucially, on the journey back to the Oort cloud, there’s an enhanced probability that one of these fragments hit the Earth."
Statistical analysis and gravitational simulations made by Siraj and Loeb raise the chances of long-period comets impacting Earth by a factor of about 10. The researchers say that their new rate of impact is consistent with the age of the death of the dinosaurs.
"Our paper provides a basis for explaining the occurrence of this event," Loeb said. "We are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs."
The study was published in Nature’s Scientific Reports.