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A pair of researchers who previously identified what may be the first known interstellar meteorite to hit Earth have provided evidence of a second body that could have originated outside the solar system, before burning up in our planet’s sky and potentially falling to the surface, according to a new study.
Amir Siraj, a student in astrophysics at Harvard University, and astronomer Avi Loeb, Harvard science professor Frank B. Bird Jr., suggest that a fast-moving meteorite exploded in a fireball hundreds of miles off the coast of Portugal. On March 9, 2017, it’s an “extra interstellar candidate object” they call Interstellar Meteor 2 (IM2) in a study published on the arXiv preprint server this week. The paper has not been peer-reviewed.
In addition to their possible origin outside the solar system, these objects appear to be unusually powerful, because they occupy the first and third places in terms of physical strength in the NASA catalog that collected data on hundreds of fireballs.
“We don’t have a large enough sample to say How Interstellar objects are much more powerful than the objects of the solar system, but we can say that they are be Siraj said in an email. “The odds of randomly drawing two objects in the top 3 out of 273 are 1 in 10 thousand. And when we look at the specific numbers related to the distribution of the objects, we find that the Gaussian odds are closer to 1 in a million.”
In a follow-up call with Siraj, Loeb added that this makes IM2 “out in physical strength”. “For us, this means that the source is different from planetary systems like the solar system.”
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Loeb has attracted widespread attention in recent years due to his speculation that the first ever identified interstellar object, known as ‘Oumuamua’, was made by space technology. Spotted in 2017, `Oumuamua streaked across the solar system and measured up to a quarter of a mile across, making it much larger than the interstellar candidate meteorites identified by Siraj and Loeb, which are just a few feet wide. Loeb’s claims of a synthetic origin for Oumuamua have drawn significant opposition from many scientists who do not consider the technological explanation as likely.
Loeb also thinks these interstellar candidate meteorites could be strange artifacts, although he and Siraj offer a mind-boggling natural explanation for the strangely powerful objects in the study: The meteorites might be a type of interstellar fragment created by the explosions of large stars, called Supernovae.
Previous observations revealed that harsh environments inside dying stars could produce objects laden with refractory elements, heavy metals, spewing out from supernovae like “cosmic lead,” according to the study.
“It has been observed that supernovae produce large chunks of iron-rich matter,” Siraj said. “This increased density of refractory elements could be where objects such as IM1 and IM2 are forming. There is a much greater mass of refractory elements available from supernovae than from planetary systems.”
Loeb, of course, keeps his mind open. “We don’t necessarily say it’s artificial,” Loeb said on the call, referring to the supernova explanation. But he added, “There is clearly a possibility that a spacecraft is designed to withstand such extreme conditions as passing through Earth’s atmosphere, so we must allow it.”
As with pretty much everything Loeb does, some in the scientific community are skeptical about his latest claim about the possibility of a second interstellar meteorite falling to Earth.
Hadrian Dephilepoix, a research associate in Curtin University’s School of Earth and Planetary Sciences, told Motherboard via email that the raw data that Loeb and Siraj pull from is labeled, and having high-level (meteorite) data from this database “a boon” has been helpful in Some applications but limited in others.
He said, “Does this mean that these sensors are bad at the function for which they were designed? The speed of a ballistic missile, it is not surprising that in some cases the speed of these fast meteors can be poorly estimated.”
He said that analyzing meteorite tracks is difficult enough with dedicated tools, and it’s an active area of research. “So without a team of meteorite track experts looking at the raw data, it is not possible to know if these struts came from interstellar tracks,” he said.
This may be where the source of such classified data – the US government – comes into play. Loeb and Siraj previously identified a candidate interstellar meteorite, called IM1, by examining a small object that exploded in the sky near Papua New Guinea after colliding at 130,000 miles per hour with heliocentrism, which means its motion relative to the Sun, which is also unusual. Fasting for a meteorite. IM2, which was about 13 times larger than IM1, hit Earth’s atmosphere at a speed of about 112,000 miles per hour, a speed that also indicates that it thrust into the solar system from an unknown location through interstellar space.
“We checked and found that this object does indeed have a central velocity of the Sun upon impact of about 50 kilometers per second,” Siraj said on the call. The “first interstellar object”, ie IM1, was “about 60 kilometers per second, when it hit the Earth, relative to the Sun. This is well above the 42 kilometers per second threshold that determines whether or not something is related to the Sun.”
The US Department of Defense (DoD) conducted an independent study of IM1 and “confirmed that the velocity estimate reported by NASA is accurate enough to indicate an interstellar path,” according to issued a statement in April 2022. Some scientists are still not convinced that the evidence makes a slam dunk case for an interstellar origin for reasons similar to those of the Devillepoix.
Loeb and Siraj will present their findings on IM1 in an upcoming study from Astrophysical Journal. They are also waiting for a response on IM2 from the Ministry of Defense, and are organizing efforts to search the sea floor for traces of exploding objects.
“There are a lot of mysteries here that we will learn something new, no matter what,” Loeb said. “I think it’s in a way a celebration of science – we need more evidence and the evidence will guide us.”