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government sensors.īecause there should be many more interstellar objects at smaller sizes, Loeb says, “there is a good chance those will appear to us as meteors, since the chances of their intersecting the Earth are higher.” Monitoring a meteor’s bright trail as it burns up in our planet’s atmosphere can reveal not only the object’s size and composition but also its trajectory and velocity with respect to the Earth and the sun.
![meteoroid that strikes the surface meteoroid that strikes the surface](https://i.pinimg.com/originals/77/43/bf/7743bffd761cb4843ade0a016a4ac8cb.jpg)
“That’s a good technique-that’s how ‘Oumuamua was found-but it really limits you, particularly in trying to figure out an object’s composition.”įor their study, Loeb and Siraj used a different method, looking for evidence of interstellar objects in more than three decades of data from the Center for Near Earth Object Studies (CNEOS), a NASA-run global catalog of meteors detected by networks of U.S.
![meteoroid that strikes the surface meteoroid that strikes the surface](https://www.scienceabc.com/wp-content/uploads/2016/07/moon-craters.jpg)
“Previous approaches to this problem were like looking for your keys under a lamppost, where our sun is the lamp illuminating its surroundings and passing interstellar objects are the keys,” Loeb explains. If confirmed, the finding could help open a new frontier in the detection and study of interstellar meteors. They detail their result in a preprint submitted for peer-reviewed publication in the Astrophysical Journal Letters. Now two researchers-Avi Loeb, chair of astronomy at Harvard University, and Harvard undergraduate Amir Siraj-say that has changed, arguing that a modest meteor observed in January 2014 was actually an outcast from another star. Scientists already know of many microscopic interstellar immigrants-cosmic rays and micron-sized flecks of stardust that occasionally strike spacecraft-but other than ‘Oumuamua, nothing larger has ever definitively been found. With an estimated size of roughly half a kilometer, ‘Oumuamua in some respects represents the tip of the interstellar iceberg just as grains of sand greatly outnumber large rocks on a beach, for every ‘Oumuamua-sized body wandering the galaxy there should be many, many more objects even smaller.
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Statistical extrapolations suggest that a quadrillion trillion similar objects may lurk as yet unseen in the dark spaces between the stars of the Milky Way, so many that there should always be one such far-flung passerby flying through the notional sphere bounded by Earth’s orbit around our star. And the recent discovery of ‘Oumuamua-a mysterious and first-of-its-kind interstellar object spied by chance when it passed close by our sun last year-confirms as much. Stars and planets routinely hurl smaller objects into interstellar space as an inescapable consequence of orbital mechanics. Yet find each other they do, and in surprising numbers. For random clumps of matter adrift in the deep to somehow find each other seems to border on the miraculous. In this cosmic ocean, so incomprehensibly desolate and vast, entire galaxies are akin to scattered spots of sea foam-not to mention the stars, planets and other lesser objects that fade to insignificance against the void. By most standards, space is exceedingly empty, containing on average just one proton per four cubic meters of volume.