The Outermost Solar System

Author(s):  
John Chambers ◽  
Jacqueline Mitton

This chapter illustrates how, until the mid-20th century, little was known about the true nature of asteroids and comets. Asteroids looked like single points of light through a telescope, and astronomers tended to think of them as miniature planets, albeit ones with somewhat more elliptical and inclined orbits. Comets seemed to constitute a separate family, distinct from asteroids. They grew much brighter as they approached the Sun, becoming enormously extended objects with a diffuse coma and one or more tails that could extend for millions of kilometers. The most puzzling aspect of comets was how they had managed to survive for the age of the solar system. Comets had such low masses that they could not be measured, yet they shed large amounts of material each time they passed close to the Sun to form their coma and tails.

Author(s):  
Karel Schrijver

In this chapter, the author summarizes the properties of the Solar System, and how these were uncovered. Over centuries, the arrangement and properties of the Solar System were determined. The distinctions between the terrestrial planets, the gas and ice giants, and their various moons are discussed. Whereas humans have walked only on the Moon, probes have visited all the planets and several moons, asteroids, and comets; samples have been returned to Earth only from our moon, a comet, and from interplanetary dust. For Earth and Moon, seismographs probed their interior, whereas for other planets insights come from spacecraft and meteorites. We learned that elements separated between planet cores and mantels because larger bodies in the Solar System were once liquid, and many still are. How water ended up where it is presents a complex puzzle. Will the characteristics of our Solar System hold true for planetary systems in general?


1803 ◽  
Vol 93 ◽  
pp. 339-382 ◽  

In the Remarks on the Construction of the Heavens, contained in my last Paper on this subject, I have divided the various objects which astronomy has hitherto brought to our view, into twelve classes. The first comprehends insulated stars. As the solar system presents us with all the particulars that may be known, respecting the arrangement of the various su­bordinate celestial bodies that are under the influence of stars which I have called insulated, such as planets and satellites, asteroids and comets, I shall here say but little on that subject. It will, however, not be amiss to remark, that the late addition of two new celestial bodies, has undoubtedly enlarged our know­ledge of the construction of the system of insulated stars. Whatever may be the nature of these two new bodies, we know that they move in regular elliptical orbits round the sun. It is not in the least material whether we call them asteroids, as I have proposed; or planetoids, as an eminent astronomer, in a letter to me, suggested; or whether we admit them at once into the class of our old seven large planets. In the latter case, however, we must recollect, that if we would speak with precision, they should be called very small, and exzodiacal; for, the great inclination of the orbit of one of them to the ecliptic, amounting to 35 degrees, is certainly remarkable. That of the other is also considerable; its latitude, the last time I saw it, being more than 15 degrees north. These circumstances, added to their smallness, show that there exists a greater variety of arrange­ment and size among the bodies which our sun holds in subor­dination, than we had formerly been acquainted with, and extend our knowledge of the construction of the solar, or insulated sidereal system. It will not be required that I should add any thing farther on the subject of this first article of my clas­sification; I may therefore immediately go to the second, which treats of binary sidereal systems, or real double stars.


Author(s):  
Owen Gingerich

In or around 1510 Nicolaus Copernicus, one of the sixteen directors of the northernmost Catholic diocese in Poland, invented the solar system. Wait a minute! you say. Wasn’t the sun always in the middle of the planets? But that wasn’t the way everyone else thought about it. Farmers, professors, priests, and school children all assumed the earth was solidly fixed in the middle of the cosmos. Every day the sun and stars revolved around the earth. The sun also moved, more slowly, in a path against the more distant stars so that it was higher in the sky in the summer and much lower in winter....


Author(s):  
John Chambers ◽  
Jacqueline Mitton

This chapter illustrates how the solar system turned out to be much larger than previously imagined. In the 2nd century AD, Greek astronomer Claudius Ptolemy, working in the Egyptian city of Alexandria, put the distance of the Sun at a mere 1,210 Earth radii, an estimate that had stood for 1,500 years. These years were a time of great scientific upheaval spurred by new instruments and techniques, and the development of powerful mathematical tools. Not only were astronomers coming to appreciate the true scale of the solar system, their entire picture of the solar system and the universe was being turned on its head. Beliefs about the solar system that had gone almost unchallenged for more than a thousand years were being called into question or overturned completely.


Lightspeed ◽  
2019 ◽  
pp. 27-48
Author(s):  
John C. H. Spence

A review of the methods the ancient Greeks used to measure the distances between the Earth and the Sun, and the Earth and the Moon, and the size of the Earth, and the lives of the personalities involved. The remarkable Jeremiah Horrocks. He was the first observer in 1639 of a transit of Venus to use it to deduce the distance from the Earth to the Sun, using the method of parallax, which is simply explained. The story of Halley’s proposal for the first international collaboration to observe a transit in 1671 and of his life. The adventures and misadventures of those who set out around the globe for this and the later transit observations of 1769, including Captain Cook in Tahiti. These produced the first reasonably accurate dimensions for our solar system.


Author(s):  
B. M. Shustov

During the second half of the 20th century and the beginning of the 21st century, space hazards multiplied, the most urgent of which is space debris. Professionals working in space are exposed to this hazard daily and are aware of it as a problem. Furthermore, increasing attention is being paid to the unpredictable behavior of the Sun, which produces the so-called space weather. The asteroid-comet hazard is considered as potentially having the most catastrophic consequences. No manifestations of biological hazard have yet been observed, although as space activities develop, it is becoming increasingly important. The appropriate time scale for astrophysical hazards is many millions of years, so from a practical perspective, they have no importance. This article briefly describes the main types of space hazards. The author analyzes the results of research and practical work in the field, both worldwide and specifically in Russia. Comparative analysis leads to the clear conclusion that a national program must be developed for the study of space hazards and to respond to space threats. This article is based on a report made by the author at the meeting of the Presidium of the Russian Academy of Sciences (RAS) on January 15, 2019.


Author(s):  
Karel Schrijver

This chapter describes how the first found exoplanets presented puzzles: they orbited where they should not have formed or where they could not have survived the death of their stars. The Solar System had its own puzzles to add: Mars is smaller than expected, while Venus, Earth, and Mars had more water—at least at one time—than could be understood. This chapter shows how astronomers worked through the combination of these puzzles: now we appreciate that planets can change their orbits, scatter water-bearing asteroids about, steal material from growing planets, or team up with other planets to stabilize their future. The special history of Jupiter and Saturn as a pair bringing both destruction and water to Earth emerged from the study of seventeenth-century resonant clocks, from the water contents of asteroids, and from experiments with supercomputers imposing the laws of physics on virtual worlds.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Q. H. S. Chan ◽  
A. Stephant ◽  
I. A. Franchi ◽  
X. Zhao ◽  
R. Brunetto ◽  
...  

AbstractUnderstanding the true nature of extra-terrestrial water and organic matter that were present at the birth of our solar system, and their subsequent evolution, necessitates the study of pristine astromaterials. In this study, we have studied both the water and organic contents from a dust particle recovered from the surface of near-Earth asteroid 25143 Itokawa by the Hayabusa mission, which was the first mission that brought pristine asteroidal materials to Earth’s astromaterial collection. The organic matter is presented as both nanocrystalline graphite and disordered polyaromatic carbon with high D/H and 15N/14N ratios (δD =  + 4868 ± 2288‰; δ15N =  + 344 ± 20‰) signifying an explicit extra-terrestrial origin. The contrasting organic feature (graphitic and disordered) substantiates the rubble-pile asteroid model of Itokawa, and offers support for material mixing in the asteroid belt that occurred in scales from small dust infall to catastrophic impacts of large asteroidal parent bodies. Our analysis of Itokawa water indicates that the asteroid has incorporated D-poor water ice at the abundance on par with inner solar system bodies. The asteroid was metamorphosed and dehydrated on the formerly large asteroid, and was subsequently evolved via late-stage hydration, modified by D-enriched exogenous organics and water derived from a carbonaceous parent body.


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