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burgess, 1988
As Voyager approached Miranda, it showed only intensely varied albedo features

Jan 25 1986 When the Voyager team saw the first close up images of Miranda, they gasped.

chevrons- bright and dark linear faults

displacement of blocks at the surface

gigantic bite

cratered grooved and jumbled

taken apart and put back together

craters- rolling hills, subdued craters of medium size

grooves from when terrain shifted downward

could the catastrophic event that turned Uranus on its side also have splashed the moons, or is their darkness the result of sunlight convertingmethane ice on their surfaces to complex organic polymers

Volcanic flows?

there are no large impact craters on miranda

the satellites of Uranus are much rockier than the satellites of Saturn, to the point where heat from radioactive decay may have led to internal differentiation.

Uranus's magnetic field is comparable in strength to, though larger than, Earth's

All the major satellites inhabit the magnetosphere, and thus sweep their zones free of plasma

satellites as small as 15 km should have been seen

geologic activity has reworked their surfaces, obliterating traces of the earlier impact events

magnetosphere particles split methane into carbon and hydrogen

faults on miranda are similar to those on Mercury

Elkins tanton 2006
Miranda's surface is old, and yet covered in strange features

coronae formed after the cratering period

Arden is surrounded by a deep canyon

canyons 100s km long and 10s km wide formed pss. by stretching of the surface by expanding underside

Miranda is too small for any significant heat from accretion to have been retained

water and ammonia or methanol would have flowed more visciously and frozen like rock

Miranda coronae geologically active- volcanic or tectonic

canyons formed from the rising of internal material and cracking of the crust

How miranda, which is too small to have any geological activity, could have evidence of upwelling is still not known

water, ammonia and methanol may be viscous enough to mimic lava

Miner, 1990
the larger satellites are large enough to be differentiated, for brighter water ice to rise to the surface, likely leading to their brighter albedos

The moons of Uranus are of comprable size to the mid-range moons of Staturn, though more geologically active

facing the sun, max temp 85 k yet water flows. fossil from past, more recent localised heating, or a mixture of water and ammonia?

resurfacing before the LHB ended, cracks probably due to ice expansion

309-319

Miranda secodn brightest albedo 32%

most eccentric

Elsinore corona has no surrounding trench and an albedo similar albedo to the surrouncding region

The perss were shown images of Miranda just 24 hours after they were taken. Too little time for any conclusions to be drawn

They had expected Miranda to be like Mimas

ancient cratered terrain indicates early history was similar to other Uranian satellites

crater rims are softened, either by ejecta or cryovolcanism

coronae and fractures postdate the early bombardment and that tehy are related

scars from bombardment were covered by recent surface materials

Soderblom: partial differentiation, heavier materials sank to the bottom and lighter (watery) materials rose. freezing and expansion fractured the surface


 * 1) 2 surface heating by tidal forces during amore eccentirc early period

Arden was originaly an impact basin, hence the concentric features around it

inverness corona formed in two massive cryovolcanic events; the first extruded dark material (like Arden) the secon had less carbonaceous material and formed the chevron seen in Inverness

the third hypothesis is that Miranda was shattered by an impact and reassembled into a random jumble. Three rock impacts created the coronae, the unbalanced mass distribnution caused Miranda to rotate so that Arden or Elsinore was pointed toweards uranus.

Then as the subsurface melted, ice rose to fill the void as the heavier material fell down

This caused miranda to reorient itself so that Arden was the Uranus facing hemisphere and elsinor was whte trailing hemisphere

the coronae could have formed form upwellings during earlier resonance periods

Miner et al 1991
James Pollack and Jonathan Lunine Satellite Origin Uranus Uni Ariz Press 1991 pp. 469-512

RH Brown et al physical properties of the Uranuian satellites pp 513-528

due to the moons pole on rotation, determining their masses from their effects on Voyager 2 was not as simple. and requiired combining info from navigation data and ground based measurements

miranda and ariel are the least spherical of the moons

bulgy, like mimas

if umbriel's peak is an impact basin, it would be the largest in the Uranian system

5% of miranda's radius

sufficiently fluid to form into a sphere, but crust has been cold and rgid not as affected by viscous relaxation

the unramian satellites are too small for their constituents to undergo significant compression

Miranda resembles the small saturnian satellites and is signficantly lower density than the other uranians

explanations for this high density have included that the co and ch4 in the nebula condensed into carbon-rich material or even graphite.

However, this is unlikely as graphite is unlikely to form in such a nebula

Uranus satellites surface protperties Veverka J Hamilton Brown R Bell Jeffrey F 528-560

miranda and ariel s pole max 87 k 86 k

20 to 30 k night time (40 years in total darkness)

methane ammionia nitrogen frozen out 2.5 m diurnal skin depth, spring would see them begin to outgas

solid state greenhouse effect

dark material on all satellites similar to asteroid f material

magnetosphere alteration of methane

endogenic origin

methane has not been identified on any uranian satellite

A popular hypothesis is that megnetospheric particles stripped methane or clathrate of its hydrogen, leaving pure carbon

geology of the uranian satellites croft soderblom pp. 561 to 628

USGS map Oberon low res only

oberon cratering ismilar to lunar highlands

grabens or contienttnal rifts and are thus interpreted as extensional topographic features

lack of an obvious crater rim (size of anaeas peak on Dione

flat plain 500 km across

Evidence for cryomagmatic flooding on oberon is controversial, with some arguing that Oberon is inert, and others arguing lower crater counts

passive extensional failure in the brittle lithosphere

titania: no 100+ km craters- these exist on other moons and so must have been covered by global volcanic resurfacing at least km thick

umbriel crater size distribution identical to oberon

extrusive cryovolcanic origin vuver spot

because all the grabens run in a general direction, they are generally seen to be part of a single event. they cut through young craters, indicating a post LHB

the origin of umbriel's uniform darkness is unclear; is it external, like cryovolcanism, external, such as an impact or a coating from a dark ring, or simply evidence that Umbriel never evolved?

bright spot on wunda indicates differentiation, so cryovolcanims is usually seen as the most likely hypothesis

It would have to be 10s of km thick and ancient to account for the dark craters

Much like Venus and Earth, Ariel and Umbriel are adjacent twins with polar opposite identities

Ariel is bright and shows multiple examples of tectonic resurfacing

least cratered cratered region

cratering suggests that earlier cratering events were covered over by volcanic resurfacing

massive impact or global-scale eruption

faulting active throughout ariel's history

this water would have the viscosity of lava

1% global expansion create faults

Astronomers expected Miranda to resemble Mimas; an inert lump covered in craters

miranda cratered terrain uniform albedo and texture

similar to the lunar highlands

of all the moons, Miranda was the most covered

craters on miranda re either very old and eroded or fresh with sharp rims

coronae darker and lighter units, crisp frresh texture and low crater density

Inverness materials like in a depression defined by mantled scarps in the north west and south

the corona is lower in altitude than the surrounding terrain, thoughdomes and ridges are of comprable elevation

eastern bound by ridge of 340 degree chasma

the ridge is overlain by coronal material at its southern and northern ends

chevron, comprised of ripples paralleling the unit's edges

Elsinore stands higher than the terrain

Arden has an albedo in line with the cratered terrain

ripple texture is not seen

inverness part of the canyon system; arden an old degraded impact basin

radial crater chains and fracture, radial ejecta

original crater 300 km wide and 10 km deep

coronae: extrusive volcanic deposits?

two global sets of fractures approximately orthogonal

multiple fresh and mantled scarp bout the ne side of the 340 chasma indicating mutiple failture events along the same fault line

canyons are all 35 +- 5 km wide and 6 to 8 km deep bounded by inward facing scarps

mantled and fresh craters indicate a single 1 km deep mantling event over entire surface

the mantling event is believed to have been formed by the same impact that formed arden

Fresh craters suggest that Arden and Inverness deposits forfmed roughly contepmeraneously shortly after the mantling event

340 degree and arden concentric chasmata are contiunuous, thus formed at around the same time, but

they cut arden deposits and are overlain by inverness deposits

if catastrophic disruption occurred (smith et al say yes, lissuar sayse no) then it must have been early enough to produce a uniform crater density

the earliest chasmata form, then the arden impact wipes out all carters smaller than 3-5 km wide

deposits of ejecta splashed against scarps

some material was sent into orbit, coming down and softening the contours of the craters

2 x 10^5 km ^3 material flooded arden basin

magmatic uplift of arden's floor may have occurred concurrently

cracks and concentric rifts formed around Arden

3 x 10^4 km^3 material erupted for Inverness Corona

10^5 km^3 for Elsinore

not surface dusting by dark meteorites there is no correlation of albedo with age the youngest features (the Mirandan coronae) also feature the strongest albedo differences

Morphologies of the canyons are quite smiliar on all moosns

characteristics of grabesn or simple faults or terrestrial contienntal rifts

R Greenberg, SK Croft et al University of Arizona Miranda pp. 693-735

4.2 degree inclination was surprising

coronae 200-300 km across

nothing except water has been detected though (+-3%) ch4, co, N nh3 may also exist

most old, heavily cratered terrain

definitely some volcanism, possibly lots

all coronae have squarish interior regions surrounded by banded concentric lines

less cratered than the surrounding terrain

abrupt, clearly defined edges

rock mass fraction of 0.2-0.4, much less than the other moons

waer-ammonia melts at 176 k, lower than pure water, making melting a possibility on a world as small as Miranda

The Uranian subnebula could have contained ammonia, but if it was spun out by a giant impact, most of the nitrogen would be in the form of N2

too viscous to be pure liquid water, too fluid to be pure solid water

the second, younger impact population apepars to be a few times greater on the leading hemisphere than on the trailing one

Miranda is too small for radeogenic heating to produce melting

3:1 resonance with umbriel could have produced a 20 k increase in temperature, enough to trigger melting. ecentricity raised to 0.1

tidal heating would have lasted for 10^8 year

clathrate has a lower conductivity than pure water, and so could have acted as an insulator, increasing temperature further

tidal heating produces stresses because it occurs over long enough times span >10^7 yr) that a cold surface is always preserved

Only ice meets the criteria for volume shift between phases to explain the surface features

grabens or continental rifts, consistent with extensional tectonics

scarps lining the rifts form much of the outer banded zone of Arden

ripples in the coronae may be compressional wrinkle ridges

tidal or radiogenic heating of 100 to 150 k produce a 1 to 1.5% volume expansion

melting and refreezing of all the water on Miranda would produce a 4-5% expansion

"sinkers"; high density anomalies sinking into a viscous aesthenesphere, though this hypothesis is difficult to prove at present, since effects predicted by the model are determined by factors as yet uknown, such as the thickness of Miranda's crust

diapirs: rising, low density material

depends on the strength of the lithospheric matierial

Elsinore contains unmistakable flow features

pure water is too difficult to heat, and its negative buoyancy makes it a bad candidate for lava

an interior containing clathrate could produce a flood of exotic ices

due to Miranda's lower gravity, cracks would have to be much longer (10-100 km) than those on Earth to allow for extrusion

features suggest viscosities of 10^8 to 10^9 P

stochastic

Bauer 2002
the near infrared spectrum of miranda: Evidence of crystalline water ice

rock mass fraction of 0.2 to 0.4

Coronae: relatively uncrated regions 200 to 300 km across surrounded on all sides by extensional rifts

Probably tectonic features that have been modified volcanically

a fluffy porous surface may indicate a history of bombardment

darker material may be polymerised ch4

miranda's composition cannot be pure water because the temperature necessary to melt it would have erased any earlier surface features, visible in cratered terrain

passing into a resonance with umbriel may have heated miranda's core to 200 k from 80 k (not enough to melt a pure ice body the size of miranda

If the water+ammonia cryomagma were a solution of more volatile substances, such as nitrogen methane or carbon monoxide, then the magma would have been loaded with gases, whcih would have led to explosive volcanism, of whch there is no evidence. Ammonia would leave traces on the surface, but has not been observed. Methane would have evaporated off completely within a few million years

Arden corona shows the most compelling evidence of surface flows

1.65 micrometre signature of crystalline water ice indicates heating events in excess of 100 k

Triton shows evidence of cry. water ice, despite half temperature (40) but no evidence of ammonia

Charon possesses ammonia, and is a better fit for Miranda than Triton

corbonaceous or silicate contaminants at 70% to lower albedo

best fit suggests a 3% ammonia solution

Presence of NH3 would favour the spin out model

Hammond, 2014
global resurfacing of Uranus's moon Miranda by convection

Catastrophic disruption has faded as an explanation for the coronae

Most astronomers accept diapirism

How tidal heating could have led to the observed surface formation has not been well described

Models of arden suggest an elastic thickness of 2 km and a thermal gradient of 8-20 k per km

past heat flow of 40-100 mW per m2

radiogenic heating is not expected to be significant

3:1 orbital resonance between Miranda and umbriel can explain Miranda's orbital inclination

Might have generated 5 GW of power; lowered ice viscosity and created a thermal gradient

models suggest that ice viscosity is so temperature dependent that it would be confined below a frozen stagnant lid

convection could have broken through the lid if its yield stress is 10kPa

Yield stress of ice may be up to 1 MPa, suggesting that tidally flexed surfaces may be anomalously weak

The number and arrangement of convective plumes is affected by core size, viscosity structure, Reyleigh number, and the distribution of tidal heating

A core radius of 0.25 can sustain convection over the widest range of rheological constraints

low order convection and surface reyleigh numbers between 10^2 and 10^3.5 creates a thermal gradient consistent with surface flexture estimates

Convection produces the concentric patterns seen in the coronae, as crust moves away from the plume heat source

The positions of all the coronae require a tidal heating pattern cinsistent with a world with no ocean

Plumes are formed near the equator, so a reoirientation is required

A 60 degree rotation from the sub-uranian point, possible solution for skewed impact crater distribution https://pubs.geoscienceworld.org/gsa/geology/article-abstract/42/11/931/131415/global-resurfacing-of-uranus-s-moon-miranda-by?redirectedFrom=fulltext

Aristotle
Comets, meteors and the Milky Way are all discussed in Meteorology

sublunar region of generation and corruption; earth air fire and water

celestial region: unchangeable, incorruptible, aither, ungenerated, indestructable and cannot be altered or increased.

"In the whole range of time past, so far as our inherited records reach, no change appears to have taken place either in the whole scheme of the outermost heaven or in any of its proper parts.

Earth at the bottom, then water, then air, then fire

Hot dry exhalations from the earth rise to the top of the sub lunar region, forming a region of fire above the region of air

this is not fire as in flame, but a kind of "protofire", which is capable of being enflamed. Later philosophers would call this phlogiston

Exhalations from the Earth are ignited by what we would now call friction due to the fire layer being dragged by the motion of the celestial sphere

1. Planets are in the zodiac, comets are not always

2. two comets can be seen at once

3. they are not among the 5 planets.

Comets were basically giant shooting stars, from a learger exhalation, slow burn

If comets' tails were due to the movement of the sphere, then they should always be seen pointing westward, and yet they always point towards the sun

Seneca= comets rise and set with the planets and stars, merely scattered outward.

comets had been visible for mroe than six months

seneca asserted that the reason comets fade is not because they burn out but because they are farther away. Would exhalations follow such stately trajectories?

"Who places one boundary for planets?" Even the planets have orbits that are different from one another

Seneca ultimately failed to develop his own theory of comets, such as explaining comets tails

Ptolemy considered comets sublunar phenomena

Olympiadorus: Milky Way does not have parallax, moon does. Also if it were the result of exhalations, its appearace would vary across the year

Ptolemy treated comets as omens heralding unfortunate events

"Teh fact that comets when frequent foreshadow wind and drought must be taken as an indication of their fiery constitution

Tycho
save the appearances (ptolemy would have looked through Galileo's telescope)

Married a clergfyma's daughter- could ot pass his estates to his children. Some in the family outraged, others grateful that the wealth would stay

lunar eclipse 1566 tycho wrote a poem proclaiming the death of Suleiman The Great. He was already dead. His cousin teased him about it and Tycho challenged him to a duel.

a gold and silver nose, alloyed to flesh colour, copper in a pinch, held on with adhesive salve.

1572: New star stella nova, brighter than Venus, age 25

"let all philosopehr's ew as well as ancient, be silent! Let the very theologians, interpreters of the divine mysteries, be silent! Let the mathematicians, describers of the heavenly bodies, be silent!"

parallax on different points on teh Earth's surface, moon showed it, the nova did not

no greater teacher of theology than the universe itself

alter baade determined type 1a

Uiversity was the province of the middle classes, bishops, scholars teachers. Tycho had never intended to pursue a academic career, until De Stella Nova

imagiary time, quark charges,

Tycho idolised copernicus but refused to countenance a moving Earth without parallax

Frederick the Great offered Tycho a chance to fund the costruction of a astronomical research establishmet on the island of Hven (After Tycho had refuesed his offer of other castles as beig a destraction from his work)

uraniborg, castle of Urania

13th nov 1577, a comet observed.

A series of bright comets after 1531 led to the realisation that a comet's tail always points away from the Sun

diurnal parallax: using the rotation of the earth (or celestial sphere) to shift your location relative to a more distant object. The moon is close enough that its parallax is one degree. Thus anything with no observable parallax or smaller than the moon must be farther than the moon

"This mieracle [nova] has made it nec essary for us to abnandon thje oppinion of aristotle and take up another: that something new can also be born in heaven... The superior Penmtates at certain times ordained by God, fabricate such new stars and comets out of the plentiful celestial matter and display them clearly before mankind as a sign of future things." Brahe

Martin Luther [brahe was a Lutheran] believed that comets were ordained by god to instil terror, as a sign of the last days.

tycho, comets refract sun's rays

Comets do not orbit the Earth and are not periodic

comets being not as perfect as planets, do not have uniform, circular motion

Tycho Brahe's instruments gave him a tenfold increase in accuracy

Tycho's observations killed Aristotianism dead.

The apeparance of three comets in 1618 formed part of a "great debate" between the followers of Tycho and Galileo.

grassi: comets are moving in a great circle that onyl appears linear when projected onto the celestial sphere

galileo said that comets could not be similar to planets, as planets rise and fall in brightness periodically as they approach or retreat from the Earth, wheras comets begin as bright and then gradually dim

comets could not be fiery objects as the celestial spheres would be cold and douse any flames

Comets were mere appearances, reflections of exhalations from the Earth. This concept didn't even last Galileo's lifetime.

Tycho's sextat was gilded with the fineries of nobility, yet aslo with reminders of its impermanence, a skeleton a withered tree. "By the sprit we live", the rest belongs to death".

tycho became a canon of the chapel housig the body of Fredericks' father. When it was demaded that he reouce his clame to the rents from land in Njordford, he refuse, ad was allowed to keep it. This sent Tycho's ego dangerously out of cotrol

He would often whisper the names of students only for them to appear as if by magic (he had in fact already called them on a bell pull)

His peasants were worked to the bone supporting Uraniborg, though Tycho arguably was no more cruel to them than he was allowed

There is nothing more problematic than a well-founded ego.

His istruments took six trained peopel three years to make

He had his own state of the art workshop on site

Tycho observed that, after observig the comet at the same point in time 24 hours later, the comet had moved 3 degrees of arc. Give that speed, then if future measuremets showed that its position was more or less than that predicted by its speed, it had to be due to parallax shift. The comet showed virtually no parallax at all, indicating it was not a meteor

Castig brith horoscopes for Frederick's Children, analysing portents in astral phenomena

the largest armillary that had ever been built

Styerborg star castle. subterranean observatory bedeced with crowned lions and inscrioptions praising Brahe

"tychonides", his future descedant would be his successor

Tycho was intensely meritocratic, and elevated promising lower class people whose talent he recognised. Tycho would often throw people with whom he disputed or their families into his own dungeon. Did they observe any of his alchemical practices?

Christian some of Frederick I visited Roskilde Cathedral in 1593

Tycho did the job of an aristocrat, holding splendid court and entertaining guests, very well

Christian was crowned in Roskilde chapel

Christian was a fan of the fad for autocracy currently sweeping Europe, and disliked Tycho's lack of deference

In 1597, Tycho's pension from the crown was discontinued. Uraniborg was closed and he moved his materials to his house in Copehagen

Tycho was gaining enemies, from the University of Copenhagen who felt he was a drain on their material and human resources, and from theologians who were less inclined towards science, or to his unconventional wedding

the peasants took advantage of this and began to complain that he was abusing his canonry

Tycho was ordered to remove his instruments from his roof, as they obstructed the King's view. He became a laughing stock at court

Tycho was exiled, essentially, to Rostock. The peasants eventually raised Uraniborg to the ground, leaving not a trace behind. Tycho the evil lord who had built over their pasture was a curse in Hven until the late 20th century

Halley
astronomy was considered mathematics, not physics

first paper while still an undergrad at Oxford. A mathematical proof derived from Kepler's laws of motion

Flamsteed: First Astronomer Royal. Flamsteed designation, Greenwich observatory under construction

By tracking the motions of sunspots, Halley and Flamsteed calculated the rotation of the Sun at 25 days, 9.5 hrs (25 days 0hrs 7 min at 16 degrees latitude)

Halley would destroy the fiction of the celestial sphere by showing that over thousands of years, stars have proper motion

By the time of Halley's education, telescopic sights had rendered Tycho's catalogue obsolete.

At the age of 20, Halley undertook an expedition to St Helena, (he declined Rio de Janeiro or the Cape of Good Hope for fear of not grasping culture and language) only to find the weather almost constantly cloudy and rain soaked

Just 341 stars, first telescopic catalogue in print

He noted that the Magellanic Clouds had the same colour and clouds as the Galaxy (ie the Milky Way)

In 1684, His father, having suffered financially from the Great Fire, committed suicide, forcing Halley to abandon his astronomical observations for a salaried position

The Royal Society demanded that Halley print the Principia at his own expense, despite his financial difficulties

He also served as Newton's editor and corrected the proofs

James Gregory, solar parallax transit of Mercury, Halley on St Helena,

He was Savilian Professor of geometry at Oxford

His father was a Yeoman Warder

Halley's first patron after his father, Jonas Moore, was Surveyor general of the Ordinance, a position headquartered at the Tower, and would play a pivotal role in the founding of the Royal Observatory at Greenwich, which Halley would eventually run.

Moore's staff likely manufactured Halley's instruments

Hooke's plan for the reconstruction of London after the fire were accepted and he designed the replacements alongside Christopher Wren

Hook had a habit of coming up with ideas and not following them through, which led him to accuse others, particularly Newton, of stealing his credit.

Charles's Oak- new constellation planisphere, dropped after 50 years because it "stole" many stars from Carina and Argo Navis

Halley was the first to work out a practical method for determining solar parallax from a transit of Mercury or Venus

He observed glitches in the orbit of the moon which Newton would show were due to the gravity of the Sun

first telescopic catalogue with a micrometer

Flamsteed called him the Southern Tycho

post principia, Halley attemtped to measure the length of a degree to learn the size of the earth

Hooke identified the Comet of 1664 with the comet of 1618. Cassini had identified the comets of 1577, 1665 and 1680

In 1681 Halley observed the Great comet of 1682 alongside Cassini. Was it the same comet as teh Great comet of 1680? did it move behind or in front of the Sun? Was it the same comet seen by Tycho in 1577?

Queen Christina had initially seen comets as omens of evil, and may have abdicated the throne of sweden after a supposed cometary warning, but by 1680 was offering prize money to anyone who could calculate its orbit

Halley's observations, directly or via flamsteed, would provide the data for Newton's chapter on comets

Newton calculated that the paths of any comet around the sun would be an ellipse due to the inverse square law

Halley's clerks salary was paid in copies of an unsalable book, the history of the fishes, the failure of which likely led to Halley having to shoulder the cost of printing the Principia

Newton letter to Halley, stumped on comets (III), not beholden to Hooke, considered suppressing it

his mother and stepfather sued him?

Halley and flamsteed's relationship soured, first over scientific disagreement, then over real or imagined claims that associates of halley were spreadng lies about him,

The orbits of the planents could be simulated using ideas without gravity, but comets could not be explained without it

Halley's comet marked the death of Agrippa in 12 BC, the defeat of Attila t Chalons in 451, and the Norman Conquest

comet fortetold the death of Julius Caesar

Newton initially thought Newton's comet was two different comets, Flamsteed did not, and never let Newton forget it

Halley also surmised that the comets were the same and believed that the sun "repelled" the comet

In 1695, Newton and Halley met to discus redoing the calculations for comets in the Principia

Halley was able to construct a table in which the position of any parabolic comet could be obtained for any position after perihelion.

in his observations, he wondered if the comets of 1531, 1607 and (later) 1682 were the same

He did however remind Newton in his letters that the gravity of Saturn and Jupiter could change a comet's predicted date

Halley was prone to sea voyages, and Newton had been appointed head of the Mint

Clairaut calculated for return of halley's comet

Astronomicae cometicae synopsis- 1726 edition; Halley asserts for the first time that the comets of 1682, 1607 and 1531 were the same, and speculates that the comets of 1456 and 1305 were the smae (they were). He predicted the comet's return for 1758.

Halley died in 1742

Charaut made the mathematical advances required to calculate the perturbation by Saturn and Jupiter

Some astronomers saw the work involved and simply gave up. Lalande and Lapaute did the work of the calculations

Perigee was a month earlier than predicted (1759)

"the Universe beholds this year the most satisfactory phenomenon ever presented to us by astronomy; an event which unique intil this day changes our doubts to certainty and our hypotheeses to demonstration" Lalande

Halley was the first to suggest, by studying Arabic records, that the moon may be speeding up and receeding from Earth

Halley, by applying Newton's laws to everyday, testable phenomena, was able to ground Newton and make him useful, moving him away from the accusations of mysticism and atheism that had so dogged his work.

halley and flamsteed historia coelestis

1676: Flamsteed and Halley had fallen out

Newton
robert Hooke: "may be fo the same nature and constitution with that of the internal parts of the earth.

The tail "is much of the same nature of the parts of a flame"

Newton concluded that the nucleus of a comet would be about a tenth to a fifteenth the size of the coma, and since that is smaller than Saturn and comets are seldom brighter than saturn, comets could not lie beyond Saturn's orbit.

Comets are free to move in any direction, whether tied to the orbits of the planets or not.

"the heavens are lacking in resistance"

At the comet's distance from the Sun at perihelion, it would be receiving 28,000 times as much heat from the Sun as Earth. At such temperatures, a vaporourous or daphenous comet would be anhillated. Comet nuclei must be durable, solid and dense. the closer a planet to the sun, the denser it is; ergo a comet that passed between mercury and the sun would be denser than Mercury. comets are the sens

a comets tail forms from interaction with the come's atmosphere, the suns heat and the particles of the ether (Kepler, only sun's rays)

comets are the densest opbejcts in the solar system

If the comet were a refracting beam, then it would be refracting off some atmosphere in the heavenly region, but the ether did not appear to have this refractory ability.

Tails grow longer as the comet approaches the sun; therefore there must exist a relationship between the length of a tail and the proximity to the sun

the vapours of comets attracted by planets mix with their atmospheres and provide ingredients for the sustenance of life (rain risen by the heat of the sun, falling on planets)

Newton speculated that comets moving too close to the Sun would be slowed down by its atmosphere, and that collisions between comets and stars may be what produces novae

Newton believed that comets could destabilise the Solar system with their chaotic orbits, until such time as God willed a reformation.

Newton said very little bout what this ultradense substance might be

a comet heated to 2000 times the brightness of incandescent iron would rarify its own atmosphere while making the nucleus shine

Newton made it possible to plot the orbits of comets precisely, and opened the way to a new form of cometary prophecy

comet caused the deluge= 8000 miles in diameter coma 100 000 miles

Kant nebular hypothesis; all the universe a large scale model of the solar system

Galileo believed that comets were optical illusions

william whiston: comests eere vast, 7-8000 miles in size, and the earth was originally one. A close approach of a comet in 2349 bc led to the biblical deluge

tail formation was newton's achiles heel

newton believed that the ether carried the particles along

but the barticles of a comet were heavier and bigger than ethereal particles

why did comets with perihelia close to the orbit of venus produce tails, when venus did not?

Newton did not believe the sun's rays played a role in the formation of cometary tails, curious

Post-Newton
Immanuel Kant, in a remarkable bit of prediction, noted that comets originated in the farther parts of the solar system, where accretion rates were too low to form into planets

He argued that comets were a natural part of the formation of the Solar System, and were as old as the Solar System itself

He argued that it was the sun's light, rather than its heat, that was responsible for the creation of a comet's tail, since comets had formed tails far from the Sun.

Comets had to be composed of light materials, light enough to be affected by the Sun's light

He also argued that the same phenomeneon that created a comet's tail also created the aurora borealis (a common speculation at the time)

Kant's book's publication was delayed for a decade after his publisher went bankrupt. By then it was overshadowed by his other philosophical materials.

In 1770, Messier discovered a comet Orbit calculated by john lexell

only 5 years How had it not been observed before? orbital calculations showed that its original orbit had been altered by the gravity of Jupiter

Leplace studied Lexell's comet's orbit, close enough to affect earth's orbit, and found its effects on earth's motion to eb negligible (if it were the sixe of the Earth, it could be expected to affect Earth's passage around the Sun by 0.1 days- <1/5000 the earth

Lapace concluded that teh actions of comets on planets, even impacts, could not have affected planetary orbits.

Laplace rejected Kant and said that heat must play a role in the formation of tails, and that comets must be made of exceptionally volatile matter to be affected so far from the sun

Laplace concluded that exposure to the sun's heat could not entirely destroy a comet, just as raising a liquid's temperature to boiling did not immediately evaporate it, but after a few revolutions it would be destroyed, just as lexell's comet had apparently been

length, straightness, bluish color (ionised carbon monoxide), radial alignment (plasma tail)lapace

lapace calculated that the chances of the planets, satellites, sun all sharing the same rotation is about 40 trillion to one. therefore they must share a common cause. Comets's orbital direction was essentially random. However their inclinations averaged about 45 degrees, leading laplace to deduce that they must have originated in interstellar space. A comet impact could be disastrous, but Earth could have passed through a comet tail numerous times without noticing

Herschel confirmed Lapplace's estimates for the sizes of cometary nuclei

Herschel: If comets shone by reflected light, then they would display phases like the Moon or venus

Francois Arago, 1819, polarised light, comets showed it, stars did not, which meant they had to shine at least partially through reflected light

David Milne 1828: fears concerning the moral influences of Comets, the production of a weak and debasing superstition, have long since been rooted out from the faith of enlightened Europe, btu they have disappereed only to be succeeded by others, respecting their physical influence

Bessell's jet hypothesis vs slowing medium for the slowing of comet encke; 2nd periodic comet, encke believed in the resistant medium. such a medium would have effets on every body in the solar system, unresolved

Bessel, halley 1835 eruption in the direction of the sun, noticed that the axis was occillating

I consider it probable that a comet's nucleus is not a really solid body; ie not a solid body of the same kind as the earth, the moon and the planets. It must be able to go easily through a state of volatility, whereas the above mentioned bodies do not possess this property or at lest possess it to a lesser degree.: the fact that its surface does not show a sharp boundary suggests that Comets consist of parts which become volatile when under the influence of heat or of some other repulsive property- bessel

Comet biela was the first to observed to split (second jup comet)

the fact that Biela's two parts did not attract each other suggested they were of exceptionally low mass

The comet did not return when predicted, however, instead, a heavy meteor shower fell

that short period comets were linked to meteor showers was established in the 1860s

Schiaparelli determined a link between comet swift tuttle, tempel tuttle and Biela Herschel: If comets shone by reflected light, then they would display phases like the Moon or venus

Francois Arago, 1819, polarised light, comets showed it, stars did not, which meant they had to shine at least partially through reflected light

Donati's comet 1858 visible for four months (9 months telescope)

formed three tails, two like antennae

the comet appeared to form dark bands separating the coma into stripes. This, according to George Phillips Bond, could only be happening if the nucleus of the comet were rotating

In the mid 19th century, experiments with electricity showed that when electric currents were passed through a very rarefied gas, such as that which existed around a comet, it produced an effect similar to that of a comet's tail.

the tail was produced by a repulsive force emanating from the sun William A Norton called it "the repulsive force of the Sun" (not sunlight)

the tail and the nucleus were not one body, but comprise particles emanating from the nucleus, which exist as a tail only for a certain time

James Clerk Maxwell (elec and mag) outlined how light itself could exert pressure on a surface suspended within a vacuum Using an incredibly sensitive machine, Russian physicist Peter Lebedev detected light pressure in 1898

In the early years of the 20th century, Svante Arrhenius applied discoveries made a decade earlier in cloud chambers, that high energy light such as ultraviolet and xrays could ionise gas and make it electrically conductive, allowing the comet to luminesce despite its low temperature

Karl Schwartzchild calculated that for comet particles to be affected by light pressure, they must be of a size comparable to the wavelengths of light, otherwise light pressure would be overwhelmed by the Sun's gravity; a calculation that was later verified in an experiment with fungus spores

repulsive force 100 times stronger- biermann- solar wind

jet effect on comet encke, shortened its orbet, expanded halley's

In 1866 William Huggins made the first detailed spectra of a comet, Tempel 1. In 1874, the arrival of Comet Coggia allowed Huggins to securely identify carbon in the spectra and connected it to hydrocarbons found in meteors and meteorites

Carbon carbyne, carbon monoxide, hydroxyl cyanogen N2 found in Coggia and in Halley's Comet in 1910

Many of these particles were ions, suggesting they must have been stripped from larger molecules

In the 1940s, Polydore Swings studies of emissions led him to conclude that the precursor molecules that formed the ionised coma material comprised ammonia, methane, cyanide, nitrogen, carbon monoxide, carbon dioxide, and water.

1950, 1951: Fred whipple,icy aggregate of comet material, dirty snowball

ices vaporise at perihelion, dispersing meteoric material below a certain size. Meteoric material above a certain size remains and forms an insulating layer, which eventually reduces the loss of gas

a comet was layered by ices in order of volatility, with water and meteoric material at the bottom

clark
1 sep 1859 bright light, as bright as lightning but rounded instead of jagged. Brighter than the surface of the sun

"flurried by surprise" "unprepared to witness" it.

the ligths had lasted just 5 minutes, but had traversed 35,000 miles (420 mph< an absurd speed for a victorian

18 hours later auroras erupted all over the world, as far nroth as acuncion, as far south as massechusetts bermuda and Georgia, then jamaica and cuba

confermation came from the magentometer at Kew, which showed that compass needles were jarred away from true north at the exact moment he noted his explosion, an even stronger one eighteen hours later

auroras all across europe for days

disabled the telegraph system, telegraph operateors got severe electric shocks

electrical currents caused the paper at telegraph offices to catch fire, nearly destroying the buildings