Far out cosmology: wandering space rocks are everywhere (Introduction)

by David Turell , Tuesday, July 16, 2019, 19:22 (1955 days ago) @ David Turell

And they may help with planet formation:

https://www.quantamagazine.org/wandering-space-rocks-help-solve-mysteries-of-planet-for...

"In 2017, a weirdly shaped rock with a strangely erratic orbit swept through the solar system, leaving as quickly as it arrived. Astronomers soon realized that it was not from around here. It punched through the planets’ orbital plane from the top down, like a dart thrown at the concentric rings of a dartboard, and it moved super fast, way too quickly to be caught in the sun’s gravity. It was also extremely dark and seemed oddly elongated, but because it was so speedy, many of its properties will remain forever mysterious.

"But it turns out that the object, the first interstellar asteroid ever observed, was not unique. It may not even be all that rare. Astronomers are coming to realize that objects like it may pepper the galaxy, perhaps in such great numbers that they influence the formation of larger worlds, maybe even entire planetary systems — including our own.

'The appearance of the asteroid, which has been named ‘Oumuamua, was a dramatic demonstration of a sea change in astronomy: the recognition that the solar system does not exist in a vacuum, at least metaphorically. No planet is an island, and no star forms in isolation. The cosmos is full of stuff that interacts across distances and time spans far greater than researchers have long appreciated, from unimaginably vast jets of gas flowing through interstellar space to ‘Oumuamua-style planetoid crumbs scattered like dandelion seeds in the wind.

"This realization is changing the way astronomers think about how star systems form. Researchers who study the birth of planetary systems have not previously considered things like astrophysical gas flows, for instance.

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"In a paper published in April in The Astrophysical Journal Letters, Bannister and Pfalzner argue that rocks like ‘Oumuamua might be catalysts for planet formation. There are probably uncountable billions of such objects sailing through the cosmos, they say. When one intersects with a billowing envelope of gas and dust surrounding a young star, it might cause turbulence and shear that stirs the gas, sculpting it into patterns that later form planets.

"In addition, they argue that ‘Oumuamua-like items might move at the right speed to become permanent residents. Infant solar systems could catch great numbers of these interstellar travelers. In their new homes, these immigrants would begin to gather smaller pebbles and dust grains, growing into larger objects. In doing so, they would provide the building blocks for pebble accretion, a theory that explains how large objects can grow very quickly into planets.

“'It’s not a huge amount of mass; it’s more their presence in the disk that would trigger it,” Pfalzner said. “It’s a seed stage. You can grow a huge tree, but it always starts from a tiny seed. It’s not the mass of the seed. It’s the potential, if you will.”

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"Stewart’s work on chondrules and Bannister and Pfalzner’s ideas about planet formation are part of an emerging understanding that even in space, everything is connected. “You have to go through a huge amount of different fields in astrophysics,” Pfalzner said: “the interstellar medium, molecular clouds, formation of stars, the disks around them, the formation of planets.”

"Data from future observatories like the Large Synoptic Survey Telescope (LSST) could intensify the need to think across many different size scales. The LSST might be able to resolve tiny pebbles in our solar system, allowing astronomers to search for more ‘Oumuamua-like objects. “I think it’s really, really exciting if our solar system is chock-full of these interstellar fragments that have come from other solar systems, that there are bits of other solar systems floating around,” Byrne said. “LSST is going to open this whole new world,” one that connects our solar system to other solar systems throughout the cosmos across time and space."

Comment: Much about planet and solar system formation is not known. We are concerned about asteroids hitting the Earth, but these other rocks flying about and coming into the solar system cannot be blocked. Luckily there is lots of empty space for them in which to roam about.