The Oort Cloud and Close Stellar Encounters
https://www.centauri-dreams.org/2021/06/...ncounters/
EXCERPTS: If we assume that the Oort Cloud, that enveloping shroud of comets that surrounds our Solar System and extends to 100,000 AU or beyond, is a common feature of stellar systems, then it’s conceivable that objects are interchanged between the Sun and Alpha Centauri where the two clouds approach each other. That makes for the ‘slow boat to Centauri’ concept I’ve written about before, where travel between the stars essentially mines resources along the way in migrations lasting thousands of years. The resulting society would not be planet-oriented.
[...] Bear in mind that at the Sun’s birth, numerous other stars would have been nearby, from which objects in their circumstellar disks could have been exchanged, along with free-floating debris in the parent star cluster and other interstellar objects. Indeed, a high percentage of the Oort Cloud’s material could have come from such sources, as the paper notes: “About half the inner Oort cloud, between 100 and 104 au, and a quarter of the material in the outer Oort cloud ≳ 104 au could be non-native to the Solar system but was captured from free-floating debris in the cluster or from the circumstellar disk of other stars in the birth cluster.”
[...] The transport of material from one star to another is seen in the simulations to be “rather symmetric.” While the Solar System is what the authors call “a copious polluter of interstellar space,” so too is it receiving material from other systems. The authors argue that stars in the Sun’s birth cluster would have experienced numerous encounters with other stars, and that the Solar System shows evidence of both single strong encounters and a series of relatively weak encounters, based on the orbital parameters of Sedna and the complexity of the orbits found in the scattered Kuiper Belt beyond 45 AU.
[...] The paper is Zwart et al., “Oort cloud Ecology II: The chronology of the formation of the Oort cloud,” accepted at Astronomy & Astrophysics. (MORE - missing details)
What if the black hole at the center of the Milky Way is actually a mass of dark matter?
https://phys.org/news/2021-06-black-hole...-mass.html
RELEASE: A team of researchers at the International Center for Relativistic Astrophysics has found evidence that suggests Sagittarius A* is not a massive black hole but is instead a mass of dark matter. In their paper published in the journal Monthly Notices of the Royal Astronomical Society: Letters, the group describes the evidence they found and how it has stood up to testing.
For several years the scientific community has agreed that there is a mass at the center of the Milky Way galaxy and that the mass is a supermassive black hole—it has been named Sagittarius A*. Its presence has never been verified directly, however, instead it has been inferred by noting the behavior of bodies around it. In this new effort, the researchers suggest that another type of mass could produce the same reactions by other bodies and in fact could help explain some anomalies that have been seen.
Back in 2014, astrophysicists were confronted with a problem they could not explain—a gas cloud that had been named G2 moved to a position close enough to Sagittarius A* that it should have been destroyed and pulled in by the black hole. Instead, the gas cloud continued on its way, unharmed.
The researchers in this new effort suggest the reason G2 was able to survive its journey past Sagittarius A*, was because Sagittarius A* is not a black hole—it is a mass of dark matter. To come to this conclusion, they created a simulation of the Milky Way, where Sagittarius A* was replaced by a mass of dark matter and then let it run. In so doing, they found the Milky Way could run pretty much the same way it would if there were a black hole at its center—nearby S-stars would behave the same, for example, as would the rotational curve of the Milky Way's outer halo. The researchers went even further, suggesting that such a mass would be composed of darkinos, which would belong to the same group as fermions. If they were to clump together, the simulation showed, they would have characteristics very similar to a black hole—the exceptions being its most extreme features.
https://www.centauri-dreams.org/2021/06/...ncounters/
EXCERPTS: If we assume that the Oort Cloud, that enveloping shroud of comets that surrounds our Solar System and extends to 100,000 AU or beyond, is a common feature of stellar systems, then it’s conceivable that objects are interchanged between the Sun and Alpha Centauri where the two clouds approach each other. That makes for the ‘slow boat to Centauri’ concept I’ve written about before, where travel between the stars essentially mines resources along the way in migrations lasting thousands of years. The resulting society would not be planet-oriented.
[...] Bear in mind that at the Sun’s birth, numerous other stars would have been nearby, from which objects in their circumstellar disks could have been exchanged, along with free-floating debris in the parent star cluster and other interstellar objects. Indeed, a high percentage of the Oort Cloud’s material could have come from such sources, as the paper notes: “About half the inner Oort cloud, between 100 and 104 au, and a quarter of the material in the outer Oort cloud ≳ 104 au could be non-native to the Solar system but was captured from free-floating debris in the cluster or from the circumstellar disk of other stars in the birth cluster.”
[...] The transport of material from one star to another is seen in the simulations to be “rather symmetric.” While the Solar System is what the authors call “a copious polluter of interstellar space,” so too is it receiving material from other systems. The authors argue that stars in the Sun’s birth cluster would have experienced numerous encounters with other stars, and that the Solar System shows evidence of both single strong encounters and a series of relatively weak encounters, based on the orbital parameters of Sedna and the complexity of the orbits found in the scattered Kuiper Belt beyond 45 AU.
[...] The paper is Zwart et al., “Oort cloud Ecology II: The chronology of the formation of the Oort cloud,” accepted at Astronomy & Astrophysics. (MORE - missing details)
What if the black hole at the center of the Milky Way is actually a mass of dark matter?
https://phys.org/news/2021-06-black-hole...-mass.html
RELEASE: A team of researchers at the International Center for Relativistic Astrophysics has found evidence that suggests Sagittarius A* is not a massive black hole but is instead a mass of dark matter. In their paper published in the journal Monthly Notices of the Royal Astronomical Society: Letters, the group describes the evidence they found and how it has stood up to testing.
For several years the scientific community has agreed that there is a mass at the center of the Milky Way galaxy and that the mass is a supermassive black hole—it has been named Sagittarius A*. Its presence has never been verified directly, however, instead it has been inferred by noting the behavior of bodies around it. In this new effort, the researchers suggest that another type of mass could produce the same reactions by other bodies and in fact could help explain some anomalies that have been seen.
Back in 2014, astrophysicists were confronted with a problem they could not explain—a gas cloud that had been named G2 moved to a position close enough to Sagittarius A* that it should have been destroyed and pulled in by the black hole. Instead, the gas cloud continued on its way, unharmed.
The researchers in this new effort suggest the reason G2 was able to survive its journey past Sagittarius A*, was because Sagittarius A* is not a black hole—it is a mass of dark matter. To come to this conclusion, they created a simulation of the Milky Way, where Sagittarius A* was replaced by a mass of dark matter and then let it run. In so doing, they found the Milky Way could run pretty much the same way it would if there were a black hole at its center—nearby S-stars would behave the same, for example, as would the rotational curve of the Milky Way's outer halo. The researchers went even further, suggesting that such a mass would be composed of darkinos, which would belong to the same group as fermions. If they were to clump together, the simulation showed, they would have characteristics very similar to a black hole—the exceptions being its most extreme features.