A meteor that streaked across the sky about 100km north of Edmonton, Canada on Feb. 22, 2021, came from an unexpected place: the Oort clouda distant region of the Solar System, well beyond the orbit of Pluto.
The 2021 event scared some residents and was captured by various instruments such as satellites and cameras. For 2.4 seconds, the meteor traveled 148.5 kilometers and formed a fireball in the sky🇧🇷 It was 10 centimeters in diameter and weighed about 2 kilograms.
With images from cameras, scientists were able to observe the details, but a new study contradicts previous measurements. It first appeared to have fallen deeper into the atmosphere than any other icy object ever seen, but it didn’t.
The new investigation calculated the object’s entry trajectory and, this time, the results were not consistent with a common inner Solar System meteor (the region between Mercury and Mars) or Trojan asteroids (around Jupiter), but rather with the orbit of a long-period comet.
Long-period comets are those with extremely elongated orbits, traveling through space for decades or centuries before approaching the Sun. Currently accepted astronomical models indicate that these the comets came from the Oort cloud.
Located at a distance of between 5,000 and 100,000 AU (1 AU is the distance between the Earth and the Sun), the Oort Cloud is the last frontier of the Solar System. It is estimated that Voyager will still take 300 years to get there and 30,000 years to leave its outer limits.
Currently, models assume that the Oort Cloud consists of a few trillion comets over 1 km in diameter and another billion about 20 km in diameter. All objects must be made of ice, never of rock, at least so the astronomers thought.
When the 2021 meteor calculated its orbit to be similar to that of an Oort cloud comet, researchers were shocked. This result suggests that the population of that region is not only composed of chunks of ice, but also of rock.
This is quite significant, as the material in the Oort Cloud is thought to be remnant from the origins of the Solar System, most of it still untouched by radiation from the Sun. Knowing that there are also rocky asteroids out there could change what is known about the formation of our cosmic neighborhood.
The study was published in the journal Nature astronomy.
Source: Nature astronomy, Western University
