There was a fireball in the sky just before dawn on February 22, 2021. The object that was hailed from the Oort Cloud wasn't a comet. The object was made of rock and behaved like an asteroid, according to data collected during its fall.
The find sheds light on the processes that formed the Solar System and challenges the idea that the Oort Cloud only holds comets. According to Karen Meech, a planetary scientist at the University of Hawaii's Institute for Astronomy, there was scattering and depositing material from all over the Solar System into the Oort Cloud.
According to Bill Bottke, a Solar System dynamicist at the Southwest Research Institute, the discovery could provide support for models that suggest objects from the asteroid belt were dispersed into the Oort Cloud. He says it's exciting. We have to figure out what we can do about it.
The Oort Cloud is a spherical halo of comets that spans out halfway to Proxima Centauri, the Sun's nearest neighbor. The lead researcher of the new study says that everything they know about it is indirect.
The Oort Cloud is thought to have become populated with comets when Jupiter and the other giant planets scattered icy objects leftover from the formation of the outer Solar System. Occasionally a star will cause an Oort Cloud object to fall into the Solar System. The long period comets are defined by their eccentric paths that take hundreds or even thousands of years to travel to the Sun.
The comet was dark and lacked a bright tail of ice. A clue that the Oort Cloud's composition may not be so homogeneity is the object's resemblance to an asteroid. It was called a Manx comet by Meech. Astronomers haven't been able to prove that the objects are asteroids because they are so small.
Researchers believe they have caught a rare object crashing into Earth's atmosphere. The work was presented today at a meeting of the division for planetary sciences of the american astronomer society.
In addition to hundreds of reports from witnesses who caught the fireball on dashboard and security cameras, Vida and his colleagues worked with images from the Global Fireball Observatory. The flare of the fireball was caught on a lightning monitor. The team was able to prove that the object came from the Oort Cloud by calculating its trajectory and observing it for 1000 years.
The object was not like other objects. The cometary fireballs fragment and burn up high in the atmosphere. This object, which plunged at 62 kilometers per second, penetrated much deeper, suggesting it was not icy. A common kind of asteroid that drops meteorites to Earth broke up at two separate pressures.
They looked at the data to see if other objects had been overlooked. In 1979 a network of fireball cameras in Canada tracked the demise of a 20- gram object that was on a long period of Oort Cloud activity. It fell through the atmosphere as well. Between 1% and 20% of the Oort Cloud must be rocky, based on the number of comets caught by the two fireball networks.
Bottke isn't sure if extrapolating from a small number of events is a good idea. The true proportion of rocky objects in the Oort Cloud may be skewed towards the low end of the estimate because they are tougher than comets.
Alan Jackson says that even if the Oort Cloud is 1% rocky, it will challenge theorists to explain how these objects got there. According to the Grand Tack, Jupiter swooped inward towards the Sun just 3 million years after the Solar System was born, before moving back out to its current position. Jackson says that in the process of doing that, it stirs stuff up, including throwing rocks in its path out to the Oort Cloud.
Meech is concerned about making too many fireball events. She wants to see more of the strange streaks on the sky. She says it is very fascinating. I hope they'll get more of them.
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