Oort Cloud News
Astronomers view the Oort cloud as a cloud of comets on the farthest periphery of our solar system. Dutch astronomer Jan Oort theorized its existence in 1950. He said that long-lasting comets are sometimes plucked from their distant orbits into the Oort cloud (perhaps by passing stars). This is how they end up in orbits that bring them closer to our sun. If it exists, Oort thought, this comet cloud is made up of material left over from the formation of our solar system 4.5 billion years ago. But is that so? Now scientists generally agree that billions of comets must reside in the Oort cloud. But in what fraction of these comets could it have originated other stellar systems? This week (August 22, 2021), two scientists said the answer could be … most.
The two scientists are Amir Siraj and Avi Loeb, both from Harvard. Loeb is also the author of Extraterrestrial, the First Sign of Intelligent Life Beyond Earth, which proposes that the first known interstellar visitor (1I / ‘Oumuamua) could have been a artificial object, made by an advanced extraterrestrial civilization. The newspaper reviewed in pairs Monthly notices from the Royal Astronomical Society published the new study by these scientists on the Oort cloud on August 23, 2021.
The study focuses on a realm of space that is between 1,000 and 100,000 times the Earth’s distance from our sun. In fact, some astronomers estimate that the Oort cloud can extend up to one light-year from our sun. By contrast, the star closest to our sun is about 4 light-years away.
Comet Borisov, the first interstellar comet
Astronomers saw the first known interstellar object, ‘Oumuamua, in 2017. In 2019, they saw a second interstellar object. This one looked more clearly cometic. Astronomers call it 2I / Borisov, or sometimes just comet Borisov. Traveling at 177,000 kilometers per hour (110,000 miles per hour), Comet Borisov passed closest to the sun and Earth in December 2019, showing a tail 14 times the size of Earth. He then returned to interstellar space.
It is the information extracted from comet Borisov that allowed Siraj and Loeb to speculate that the Oort cloud is made up mainly of interstellar visitors. Scientists admit that information about comet Borisov still has some degree of uncertainty. But even with these uncertainties, scientists said their calculations show that interstellar objects are more numerous than objects in the solar system in the Oort cloud. Siraj commented in a statement:
Before the detection of the first interstellar comet, we had no idea how many interstellar objects there were in our solar system. But the theory of the formation of planetary systems suggests that there should be fewer visitors than permanent residents. We now check that there could be a substantial number of visitors.
Interstellar objects are dark and distant
If the Oort cloud contains perhaps billions of interstellar objects, why haven’t we seen more? Siraj said it’s because we don’t yet have the technology to see them. First think about how far away the Oort cloud is. The Earth’s distance (93 million miles, or 150 million km) is called the astronomical unit (AU) of the sun. Tiny Pluto is about 40 AU from the sun. The even smaller comets in the Oort cloud are about 1,000 to 100,000 AU. But remember that comets do not shine by their own light. They only reflect the light of our sun. Thus, a comet in the Oort cloud, interstellar or otherwise, is too far from the sun, too faint, and too small to see directly. Therefore, we see comets – and speculate with an Oort cloud – only thanks to those comets that are dislocated from the Oort cloud and reach our part of the solar system.
Could there be interstellar objects closer to Earth?
Matthew Holman, former director of the Center for Astrophysics Minor Planet Center, who did not participate in the research, wondered if the abundance of interstellar visitors to the farthest regions of the solar system could translate into some interstellar visitors. closer to the sun. He said:
These results suggest that the abundances of interstellar and Oort cloud objects are comparable closer to the sun than Saturn. This can be proven with current and future surveys of the solar system. When we analyze asteroid data from this region, the question is: Are there asteroids that are really interstellar that we didn’t quite recognize before?
There are asteroids that scientists have detected but have not tracked over the years. Holman reflected:
We think they are asteroids, and then we lose them without taking a detailed look.
Co-author Loeb added:
Interstellar objects in the planetary region of the solar system would be rare, but our results clearly show that they are more common than solar system material in dark areas of the Oort cloud.
Future searches
The Vera C. Rubin Observatory, currently under construction in Chile, should help astronomers find more visitors from outside our solar system. Siraj commented that the new observatory:
… blow up previous searches for interstellar objects out of the water.
The first light for Vera Rubin’s engineering camera is expected in October 2022, and full survey operations are expected perhaps a year later.
Also scheduled for 2022, the Transneptunian Automated Occultation Survey will operate three medium-sized telescopes at the San Pedro Mártir National Astronomical Observatory, a mountain range in Baja California, Mexico. This system is specifically designed to find small bodies on the outer edges of our solar system. Maybe it will open the door to more interstellar objects. Siraj said:
Our findings show that interstellar objects can place interesting constraints on the formation processes of the planetary system. [A large number of interstellar objects in the Oort Cloud] requires expelling a significant mass of material [from our solar system] in the form of planetesimals. Along with observational studies of protoplanetary disks [disks around newly forming stars] and computational approaches to planet formation, the study of interstellar objects could help us unlock the secrets of how our planetary system and others were formed.
Conclusion: Scientists ’calculations show that most comets in the Oort cloud can be interstellar objects or visitors from beyond our solar system.
Source: Interstellar objects surpass objects in the solar system in the Oort cloud
Prepress to arXiv: interstellar objects outperform solar system objects in Oort cloud
Via Harvard and the Smithsonian Center for Astrophysics