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By Jason Davis
Oumuamua may not have been the first visitor to another stellar system, after all.
When the mysterious stadium-sized object flew over our sun in 2017 before disappearing from view, scientists thought they were witnessing a rare event. But a new document suggests that a pint-sized object resembling Oumuamua arrived in 2014, briefly flickering as a meteor in the heavens over Papua New Guinea.
The authors of the journal, Harvard astronomer Avi Loeb and Harvard's first cycle student Amir Siraj, took data from a global network of US government sensors designed to search for missiles in the sky and instead searched for meteors moving fast enough to come from outside our solar system. They found an object the size of a meter that hit the Earth at 37 km / s. In tracing his way, he concluded that he was coming from interstellar space.
The object is thought to have disintegrated before reaching the ground, but its existence raises the possibility that interstellar objects can be studied first-hand. Loeb said the government system could be altered to alert scientists when a fast-moving meteor is detected, so that they can search for fragments that have survived to the ground.
"It's a new way to look for interstellar objects," said Loeb, who raised eyebrows in 2018 when he said: "Oumuamua could have been an alien spacecraft." That spares you the trip. You do not have to go on another planetary system. You get material objects that you can potentially examine. "
If confirmed, the discovery of the meteor means that our solar system has been visited by two interstellar objects in only three years. According to Loeb, this implies that there should be at least a million more objects that we can not see whistling through the internal solar system at any given time, and that an interstellar meteor hit the Earth every 10 years.
Seed life on earth
Astronomers have long hypothesized that asteroids or comets could have transported to the ancient Earth the organic molecules that have become the basic building blocks of life. But no rule says they must come from our own solar system.
Asteroids are more rocky, while comets are more icy. Oumuamua looked like an asteroid, but moved like a comet, spewing gas in its wake. Once one of these objects enters our atmosphere, it becomes a meteor and any room that survives to the ground becomes a meteorite.
The possible discovery of an interstellar meteor raises an intriguing possibility: scientists could possibly be able to examine interstellar meteorites to determine if they could transport life between star systems.
"We suspected that panspermia, the seeding of life between planets and planetary systems, could help spread life in our galaxy," said Franck Marchis, planetary astronomer of the SETI Institute in Mountain View, California. "It will be great to get a fragment of [an interstellar meteor] to really understand the conditions of the long journey between the stars. "
He added that such a trip could last millions of years and that any organic molecule should be well protected to survive.
Just an old meteor?
Not everyone is convinced that the meteor identified by Loeb and Siraj originated in our solar system. The government will not say how accurate its sensors are, so it's impossible to know how much the actual speed and direction of the object matched those reported.
"I do not think we can exclude the limit [inside our solar system] trajectories based on available evidence, " Quanzhi Ye astronomer of the California Institute of Technology announced on Twitter. Peter Brown, a meteorite astronomer at the University of Western Ontario, described the uncertainties as "gigantic red flags," adding, "It is very difficult to measure orbits and velocities with sufficient precision to say definitively: "This one is interstellar. & # 39; "
Loeb and Siraj addressed the uncertainties in their paper by referring to two previous studies comparing government sensor data with the results of known and calibrated sensors. One study found that meteor speeds could be altered by 28%, but Loeb said it would take a 45% speed error for the Papua New Guinea meteor to originate from the solar system.
Many objects
Scientists could possibly use telescopes equipped with special equipment to observe interstellar meteors to ignite in the atmosphere and decode their compositions from traces of burning gas that they leave in their wake. This could mean more opportunities for scientists studying asteroids and comets to learn about the formation of other star systems.
"We want to be able to understand how planetary building blocks have formed around our sun," said Michele Bannister, a postdoctoral researcher at Queen's University in Belfast, Northern Ireland. "Has this happened in the same way with the other stars? It's the fundamental process that we're trying to dig here: how did the building blocks of the planets form and have- they grew up? "
Bannister said she was not yet convinced that Papua New Guinea's meteor was coming from outside the solar system, "but they are asking the right scientific question," he said. she says about Loeb and Siraj.
In an unpublished article, Loeb hypothesizes that interstellar meteors might be a way for extraterrestrials to communicate with Earthmen, though he admits that the idea is far-fetched: "Some d & # s; 39, between them could even represent obsolete technological equipments of extraterrestrial civilizations, which drift towards the Earth chance, like a plastic bottle carried on the bottom of natural shells. "
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