Using statistical analysis and gravitational simulations, Harvard University astrophysics student Amir Siraj and astronomer Avi Loeb calculate that a significant fraction of long-period comets originating from the Oort cloud, an icy sphere of debris at the edge of the solar system, can be thrown off course by Jupiter’s gravitational field during its orbital motion. They publish results in Nature Scientific Reports.
“The solar system acts like a kind of pinball machine”Siraj explains in a statement. “Jupiter, the most massive planet, propels long-period incoming comets into orbits that bring them very close to the sun.”
During close passage to the sun, comets may experience powerful tidal forces They smash chunks of rock and ultimately produce cometary shrapnel.
“At a sun scraping event, the part of the comet closest to the sun feels a stronger gravitational pull than the part that is further away, which results in a tidal force through the object, “says Siraj.” You can get what’s called a tidal disruption event, in which a large comet breaks into many smaller pieces. Most importantly, on the journey back to the Oort cloud, there is a greater chance that one of these fragments will hit Earth. ”
New calculations of Siraj and Loeb’s theory increase the chances that long-period comets will impact Earth in a factor of about 10, and show that about 20% of long-term comets become solar scrapers.
The pair say their new impact rate is consistent with Chicxulub’s age, providing a satisfactory explanation for its origin and other similar impactors.
“Our article provides a basis to explain the occurrence of this event“says Loeb.” We are suggesting that, indeed, if you break an object when it gets close to the sun, it could lead to the right event rate and also the kind of impact that killed the dinosaurs. ”
The evidence found in Chicxulub crater suggests that the rock was composed of carbonaceous chondrite. Siraj and Loeb’s hypothesis could also explain this unusual composition.
A popular theory about the origin of Chicxulub states that the impactor originated in the main belt, which is a population of asteroids between the orbit of Jupiter and Mars. Nevertheless, carbonaceous chondrites are rare among main belt asteroidsBut they are possibly widespread among long-period comets, providing additional support for the cometary impact hypothesis.
Other similar craters show the same composition. This includes an object that struck about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth’s history, and the impactor that left the Zhamanshin crater in Kazakhstan, which is the confirmed crater. largest in the last million years. The researchers say the timing of these impacts backs up their calculations of the expected rate of comets disrupted by Chicxulub-sized tides.
Siraj and Loeb say their hypothesis can be tested by further studying these craters, others like them, and even those on the moon’s surface to determine the composition of the impactors. Comet sampling space missions can also help.
In addition to the composition of comets, the new Vera Rubin Observatory in Chile You can watch the long-period comet tidal disruption after it goes live next year.
“We should see smaller fragments reaching Earth more frequently from the Oort cloud”says Loeb. “I hope we can test the theory by having more data on long-period comets, get better statistics, and maybe see evidence for some fragments.”
Loeb says that understanding this is not only crucial to solving a mystery in Earth’s history, it could prove critical if such an event threatened the planet. “It must have been an incredible sight, but we don’t want to see that again,” he said.