‘Interstellar’ fireballs likely came from our solar system, study suggests

A suspected interstellar fireball discovered over the Pacific Ocean in 2014 likely came from our solar system, according to new statistical modeling of the meteor and others like it.

The new study also concluded that debris from the fireball would not have survived passing through Earth’s atmospherewhich means that the claimed restoration of fragments from it must have a different, more mundane origin.

These results were obtained by an international team of European and American astronomers led by Maria Hajdukova from the Astronomical Institute of the Slovak Academy of Sciences. After studying the height and speed of the 2014 fireball, as well as hundreds of others in NASA‘s Center for Near-Earth Object Research (CNEOS) they found that the fireball information did not include the error range for each measurement. The margin of error is the level of inaccuracy of any scientific observation. The problem, as Haidukova’s team explained, is that this inaccuracy can meteors native to our solar system it seems as if they came from interstellar space.

Fireballs are the brightest of the meteors, and from the ground they can be seen as a falling fireball, streaking across the sky and then disappearing. Most shooting stars are the product of tiny dust particles a millimeter or less in size, but a fireball can be created by a meteoroid the size of a rock. (Meteoroid is what these objects are called while they are in space; when we see them fall through the atmosphere we call them meteors, and those that survive the fall and reach the ground are called meteors. meteorites.)

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Harvard astronomer Avi Loeb, who is no stranger to controversial claims about interstellar objects, and his Harvard colleague Amir Siraj argue that the fireball observed over Papua New Guinea on January 8, 2014 and detected by US Department of Defense sensors is likely came from outside our solar system. They believed in it so much that they even launched a private, cryptocurrency-funded expedition to the Pacific Ocean to scour the ocean floor for debris from the fireball. They found “spherules” that they claim have a composition that marks them out as interstellar in nature. However, independent analyzes The spherules by Steven Desch of Arizona State University and Alan Jackson of Towson University in Maryland suggest that they are nothing more than industrial waste from burning coal.

Now Hajdukova’s team, which includes Desch and Jackson, has also quantitatively shown that the fireball was unlikely to be interstellar in nature, but was most likely native to our solar system.

finger pointing at a small metal ball on the screen

One of the metal spherules believed to belong to an interstellar meteorite, found by astronomer Avi Loeb. (Image credit: EYOS)

Loeb and Siraj staked their interstellar claims on data in the CNEOS catalog that appears to show the fireball was moving at 27.8 miles (44.8 kilometers) per second relative to the Sun when it entered Earth’s atmosphere . This is greater than the escape velocity of the Solar System, which varies with distance from the Sun. Sun but in EarthThe orbit is 26.2 miles (42.1 km) per second. This excess speed means that the meteoroid would not have moved in an orbit associated with the Sun. Instead, its orbit would be hyperbolic, that is, not closed around the Sun, and it would come from somewhere outside the Solar System. Astronomers have already seen objects with hyperbolic orbits in the form of two currently confirmed interstellar objects: 1I/’Oumuamua And 2I/Borisovwhich originated around another star and were passing through our solar system at the time of their discovery.

It is estimated that there may be up to 10,000 such interstellar objects in the Solar System at any one time. timeso we might expect interstellar meteoroids to create fireballs from time to time. However, estimates of the population of small interstellar bodies in our solar system suggest that an interstellar fireball should be an extremely rare phenomenon. However, Loeb and Siraj report not just one interstellar fireball, but two: an event in 2014 and another recorded on March 9, 2017, over the North Atlantic Ocean off the coast of Portugal.

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Haidukova’s team began analyzing the CNEOS fireball catalog with two goals in mind. First, it was necessary to determine whether the meteorite fragments could survive the re-entry of a meteor moving at hyperbolic speed, and second, whether any fireballs in the CNEOS catalog actually have hyperbolic orbits.

The catalog contains entries for 954 fireballs (as of March 2023), but altitude and speed data are available for only 291 of them. Of these, six had orbits that could potentially be hyperbolic, according to the new study.

The problem with the claim that some of them are interstellar is that the range of errors – the imprecision of the measurements – is on the same level as the amount of excess velocity required to make the orbit hyperbolic. It is very difficult to distinguish between these two phenomena, and as long as this inaccuracy remains, it is impossible to definitively state that the fireball is in a hyperbolic orbit. In other words, data describing fireballs should not be taken at face value until the range of errors in speed measurements has been examined.

Through statistical analysis, Hajdukova’s team found that it is likely that a catalog of purely solar-related fireball-producing meteoroids will contain at least one event that looks like it could be interstellar, but is actually not so due to inaccuracy in measurements. For 291 fireballs with altitude and velocity data, the researchers found that there was a 53% chance that one would disguise itself as an interstellar fireball. When scaling the entire population of the CNEOS catalog (~1000 objects), this probability increases to 93%.

“We conclude that, based on the available data, we do not find any evidence to support the interstellar origin of any of the nominally hyperbolic bolides in the CNEOS catalog,” Hajdukova’s team writes in the new paper.

What’s more, their work suggests that even if one of the fireballs had hyperbolic speed, not a single piece of debris would survive to reach the ocean. The meteoroid will simply evaporate due to heating from atmospheric ablation – this is what leads to the short-term “ignition” of the fireball. Therefore, what Loeb and Siraj’s team found on the ocean floor could not have been the result of an interstellar fireball, further supporting the conclusion that the spherules are just terrestrial industrial waste. Hajdukova’s team notes that if the fireball had moved at a slower speed, which kept it tethered to the Sun, then its fragments might have reached the ocean, but then they would have been simply solar system debris, no different from any other meteorite. that reach the surface of the Earth.

Their results also have broader implications for astronomers studying small pieces of space debris. It’s possible that it’s not just the supposed hyperbolic fireballs that have overestimated velocities; This can be a common mistake even when studying regular fireballs. Because fireballs and meteors are debris from larger objects dating back to the dawn of the Solar System, tracking the origins of fireballs and meteors is an important part of studying the history of the Solar System and estimating the population of small bodies in the inner Solar System. If the rates were overestimated and the size of the small debris populations wrong, perhaps the story needs some subtle changes.

The study was published Oct. 25 in the journal Astronomy and astrophysics.

‘Interstellar’ fireballs likely came from our solar system, study suggests

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