Bizarre Solar System Discoveries of the Planets That Will Make Your Hair Stand Up

in a little over six decades we've met every one of the planets in our solar system traveling at first to our nearest neighbors we visited venus mars and mercury and found rocky planets covered with the remains of long lost worlds each has a life that followed very different paths to these planets we returned time and again staying longer on each visit exploring deeper and even touching down onto alien ground then we ventured further beyond the rocky worlds beyond the ice line and out to the land of the giants as we explored jupiter and saturn we began to piece together the extraordinary life story of these gas giants and all the exotic moons in their grasp but that was just the beginning beyond saturn out there far into the darkness lie the most distant planets of the solar system worlds we can hardly even glimpse from earth uranus a pale blue marble hanging in the frozen depths of space further out its icy sibling neptune and beyond that pluto a world but not a planet which until now has remained virtually hidden from us in all but name each lies not millions but billions of kilometers from earth and for this reason only once have we dared to visit them and capture a set of images from the dark precious data that allows us to begin to understand the endless mysteries that lie out there at the outer edges of our solar system and beyond the scale of the solar system is virtually unimaginable a landscape laid out across distances impossible to comprehend within the realms of human experience london to new york is five thousand five hundred kilometers london to sydney a mere seventeen thousand kilometers while london to the moon is 384 000 kilometers and the longest single journey any human has ever completed the equivalent of traveling nine and a half times around the circumference of earth beyond these journeys as we look out towards ever more distant destinations the numbers grow so big so quickly that we've had to invent a different unit of distance altogether in order to give us a containable scale for the vastness of the cosmos it's based on the mean distance between the earth and sun which is 149 million 598 000 kilometers known as one astronomical unit or one a you today we can measure this distance with relative ease but calculating that number for the first time with any accuracy was far from an easy task for near on two thousand years many a great mind took measurements made calculations and came up with numbers that estimated the distance to the sun but it wasn't until the 17th century that we were able to measure for the first time the distance to our star when joseph kepler provided the mathematical underpinning and edmund halley the understanding that the transit of a planet could unlock our ability to accurately calculate an astronomical unit halley was the first to realize in 1716 that by measuring a transit of venus the moment our sister world passes directly between us and the sun from different positions around the globe we could obtain the necessary numbers to allow the geometry to play out unfortunately for halle he had the right idea at the wrong time as transits of venus are enormously rare coming in pairs approximately once every 120 years so in one of the great scientific baton passes of all time halle left behind detailed instructions for future astronomers to carry out his plan 20 years after his death the 1761 transit of venus provided the first opportunity to put his theory to the test in a remarkable combination of collaboration and competition which occurred in the middle of the anglo-french seven years war observers from both these countries traveled all over the world to destinations as far afield as siberia madagascar newfoundland and the cape of good hope praying for a clear sky to observe and measure the transit combined with a similar set of expeditions for the next transit eight years later enough data was gathered to allow the french astronomer jerome lalonde to calculate the distance between the earth and the sun for the very first time coming up with a pretty accurate figure of 153 million kilometers today we no longer need to rely on the rarest of astronomical events to make these measurements instead we have far more direct ways of measuring that have allowed us to plot our journey around the sun in ever greater detail throughout a year as we follow our elliptical orbit around the sun the distance from our planet to the center of the solar system varies enormously this means that in early january each year as we reach the closest proximity to our star known as perihelion we are about 147 million kilometers distant six months later in early july we reach epihelion our furthest distance from the sun and find ourselves about five million kilometers further away orbiting at around 152 million kilometers away exactly what one astronomical unit actually is has therefore been the subject of intense debate and change over the last century and as we have sent our robotic explorers across the solar system our ability to directly measure the precise distances between the inner planets using radar and telemetry has yielded endless refinements so since 2012 we or the international astronomical union on our behalf have made life much more straightforward by defining 1au as 149 billion 597 million eight hundred and seventy thousand seven hundred meters or about one hundred and fifty million kilometers mars the furthest out of the four rocky planets sits at one point five a u half as far away from the sun again as we are at 2.2 au the asteroid belt begins a swirling carousel of rocks and failed worlds it stretches out for another 150 million kilometers before coming to an end here at the snow line of our solar system 3.2 a you away from the sun we leave the rocky worlds behind and continue across another 300 million kilometers of space before we reach the first of the giants jupiter and yet here at 5.2 au 780 million kilometers from the sun our journey has only just begun it is almost double the distance again before we reach the next planet the ringed jewel that is saturn sitting 9.6 au or 1 434 million kilometers from the center it is here that the realm of our exploration ends at the last of the planets that we can say we have truly explored mercury venus mars jupiter saturn each one a world that we have not only visited but resided around our robotic explorers orbiting with camera eyes wide open for years at a time in many cases we've not just looked at but also touched the surface of these worlds and the moons they embrace once we get beyond saturn the scales change so much the distances grow so vast and travel times so long that they are measured not in days and months but years and decades uranus the first of the ice giants sits over twice as far away from the sun as saturn orbiting at an average distance of 19.2 au or 2.871 billion kilometers then neptune the farthest of the planets lies another 11 a.u further out and orbits nearly 4.5 billion kilometers away from the sun after it comes pluto on the highly elliptical orbit that takes it inside and outside the line of neptune but on average sits 5.9 billion kilometers away from the sun to reach these worlds is so difficult that in our 60 years of planetary exploration we visited each only once and spent just the briefest of moments in close proximity to them we manage a matter of hours in each system as our spacecraft are propelled at enormous speeds so fast that they quickly fly past and beyond but the pressure scraps of data they have returned have allowed us to peer through the mysteries that lie out there at the outer edge of our solar system and start to tell the extraordinary stories that reach deep into the darkness [Music] to reach the outer planets has taken the work of perhaps the greatest of all of our planetary explorers at the time of writing in january 2019 the voyager 2 spacecraft has been in continual operation for 41 years 4 months and 19 days traveling at 15.341 kilometers per second it is currently around 119 a.u from the sun that's 17 billion kilometers away and has just recently been officially deemed to have entered interstellar space no longer within the empire of our sun the heliosphere created by the solar wind that defines the boundary of our solar system this little probe weighing less than a family car is the third human-made object after its sibling voyager 1 and also pioneer 10. to leave our home star system behind as it heads out into the void it is expected to continue to stay in contact with us here on earth for at least another six or seven years transmitting its weak radio signals until at least 2025 before slipping off into its final silence around 48 years after its launch on its way towards a small star called ross 248 located in the northern constellation of andromeda it all began on the 20th of august 1977 when the voyager 2 spacecraft left our planet on board a titan iii rocket taking off from launch complex 41 cape canaveral air force base two weeks later on the 5th of september the twin probe voyager 1 would follow hot on the heels of its sibling taking the fast lane voyager 1 would speed ahead reaching jupiter four months earlier than voyager 2 which had been sent on a different trajectory that took it on a slower longer more circular course making its closest approach on the 9th of july 1979. voyager 2 swept past jupiter at a distance of 576 000 kilometers from the planet's cloud tops gathering a vast amount of data on the giant planet's atmospheric characteristics and its moons this included the first detailed analysis of the swirling storm known as the great red spot as well as a 10 hour analysis of the volcanoes of io allowing the activity to be calculated by directly comparing the images of the moon with images voyager 1 had taken just a few months before using jupiter as a gravitational springboard voyager 2 then left the jovian system behind and continued on a two-year journey to saturn with its closest approach occurring on the 26th of august 1981 voyager 2 became the third spacecraft to visit saturn providing a vast range of pictures and data on the planet its rings and moons but it was the next leg of its journey that would be truly groundbreaking and it was only possible because of the rarest of celestial alignments back in 1964 gary flando an aerospace engineer working at the jet propulsion laboratory in pasadena california noticed that an unusual configuration of the four outer planets would occur in the late 1970s and early eighties flando realized that this particular alignment which occurs once every 175 years would potentially allow a single spacecraft to visit all the outer planets using a series of flybys and gravity assists that would provide an opportunity to visit not just jupiter and saturn but uranus and neptune for the very first time over the next 15 years nasa began plotting a mission to complete what became known as the grand tour various plans for the tour were started and shelved as the costs and feasibility of the proposed route came into question until eventually in 1972 the twin probe mariner jupiter saturn project was approved with an estimated cost of 360 million dollars the two probes would eventually be renamed the voyagers and only one would complete the grand tour voyager 1 would be sent from jupiter to saturn and then onto its satellite titan to attempt to explore the moon in its intriguing atmosphere but voyager 2 would be given the grandest of journeys and the honor of becoming the first craft to attempt to see uranus and neptune close up flying past the saturnian system in late august 1981 voyager 2 began a journey into the darkness that has yet to be repeated over the next three and a half years the craft would make its lonely journey outwards towards its unique encounter with the third largest planet in the solar system a planet that until then we had only ever been able to peer at in the distance the seventh rock from the sun sits two point billion kilometers from the earth a pale blue marble hanging faintly in our night sky barely visible with the naked eye ancient observers dismissed the object as a star too slow and too dim to join the family of planets it wasn't until the invention of the telescope that the real character of this distant object began to emerge but even then the discovery of uranus was a slow one it began on a cold march night in 1781 tuesday the 13th between 10 and 11 pm to be precise in the townhouse garden of william herschel as the 43 year old astronomer peered through his 160 millimeter telescope surveying the sky that night for any small stars he could bring into view he noticed a dim object that over the course of the next few days appeared to be slowly moving so he assumed it must be a comet reporting his findings to the royal society the following month herschel still seemed convinced that this was a comet not a planet even though he himself suggested that the characteristics of the observation were as planets are the astronomer royal at the time neville masculine whose claim to fame as being the first person to measure the weight of the earth scientifically for the first time wrote to herschel in late april 1781 to share his bafflement i don't know what to call it he wrote it is as likely to be a regular planet moving in an orbit nearly circular to the sun as a comet moving in a very eccentric ellipses [Music] eventually the accurate computation of the body's orbit calculated by a number of different astronomers provided the ultimate proof of its character and its planetary status was confirmed by herschel in a letter to the president of the royal society sir joseph banks in 1783 sir by the observations of the most eminent astronomers in europe it appears that the new star which i had the honor of pointing out to them in march 1781 is a primary planet of our solar system with that the seventh planet was born into our story of the solar system but naming this new arrival the first planet to require such a decision since antiquity was far from straightforward the announcement of herschel's discovery had not only impressed the world of science but also captured the attention of the higher reaches of british society all the way up to king george iii as a reward for his historic achievement herschel came under the patronage of the king to the tune of 200 pounds a year and moved to windsor to allow the royal family the use of his telescopes herschel had the perfect response in mind to return such favors charged with the responsibility of naming the new planet he proposed the name georgium cetus george's star after the king himself however the name met with immediate opposition away from british shores so other more universal alternatives were proposed including herschel neptune and uranus after the greek god and father of saturn amazingly georgium cedars continued in some usage for the next 70 years but by 1850 when his majesty's nautical almanac office finally caved in the name was switched to uranus and it finally and permanently stuck it would be 136 years later across 2.6 billion kilometers of space when the planet that was discovered in the back garden of a somerset town house would slowly expand into the viewfinder of voyager 2. approaching it at 17 kilometers per second after a journey of over eight and a half years our first and only close encounter with this most enigmatic of planets would play out within a matter of just six or so hours remarkably little was known about uranus as the spacecraft began the observatory phase of its mission in early november 1985. we knew this world was the third largest by volume after jupiter and saturn and that it took a leisurely 84 years to complete a single highly elliptical orbit but we could only estimate the length of its day to be somewhere between 16 and 24 hours we also knew its composition was substantially different to the two gas giants with higher amounts of water ammonia and methane compared with its bigger neighbors but how this formed an atmosphere and what dynamics played out beyond the pale blue mist was a mystery we also knew that it had at least five moons tiny points of light in orbit that we had detected with telescopes from earth but again what form these moons took and what features they held remained a complete mystery as was a faint and narrow set of rings around the planet that had only been discovered a few years earlier what these rings were made of and why they had formed from such dark material compared with the glowing rings of saturn was yet another element that needed exploration but perhaps the most mysterious of all was the fact that the whole uranian system had the strangest of orientations the planet's rotation its moons and its rings all appeared to be tipped up on the side rotating around a horizontal rather than a vertical axis in contrast with every other planet in the solar system as astrobiologist david grinspoon explains the iranian system really stands out in the solar system in several ways but the most striking way visually is that it's tilted on its side almost completely so that the north pole of uranus sometimes points right at the sun and it's always in that plane of the orbits and the moons as well are orbiting in that extremely tilted plane so the whole system forms this sort of bullseye pattern that is rotating at this odd angle around the sun at 9 59 pst on the 24th of january 1986 the spacecraft flew just over 500 kilometers above the cloud tops of uranus at its closest proximity to the target back on earth receiving stations looked up to the sky impatiently pointing their giant antennae towards the far explorer in anticipation of the first of its faint radio signals but for all the anticipation and expectation of a mission that had been decades in the planning years in transit and with a catalogue of extraordinary revelations already behind it the first impressions were perhaps a little underwhelming the first images returned by voyager revealed a beautiful but featureless world a pale blue orb hanging in the frozen reaches of our solar system that was covered in an unbroken haze in striking contrast with the dynamic realms of jupiter and saturn that voyager had revealed to us in such detailed beauty peering into the haze only 10 cloud features could be seen across the whole planet blown around by winds traveling in the same direction as the planet rotated but despite the sameness of first appearance slowly but surely the data that voyager returned would change our understanding of almost every aspect of this world voyager was able to measure the rotation of the interior of the planet for the first time revealing that a day on uranus lasted for 17 hours and 14 minutes beyond that it also revealed uranus to be a bitterly cold world with the average temperature being an icy minus 213 degrees celsius in fact we now know that uranus is the coldest planet in the solar system and with such cold comes a stillness the lack of internal heat helping to explain the inactivity of its atmosphere why uranus internal heat appears to be so much lower than that of the other giant planets is still poorly understood [Music] as voyages spread past it also attempted to measure the composition and structure of uranus as expected the most abundant ingredients in its atmosphere were found to be hydrogen 83 and helium 15 although the amount of helium was lower than many scientists had predicted the relatively high level of methane measured in the upper atmosphere at 2.5 percent also provided an explanation for the aquamarine blue glow of the planet that we'd seen from afar for so long but understanding more about the planet's internal structure was not quite so straightforward [Music] at roughly 14 and a half times the mass of the earth uranus consists mostly of water ammonia and methane in the form of ices that we believe are wrapped around a rocky core however the exact masses that make up each of these layers and the amount of each of the individual constituents was beyond the measuring capabilities of voyager so even today we can still only estimate the exact makeup of the planet however the data returned by voyager did result in one major change in our understanding of the planet's interior with the knowledge that the composition of uranus and soon neptune was substantially different from the gas giants of jupiter and saturn a new category of planet was defined in the 1990s from the data the spacecraft gathered uranus is one of two ice giants in our solar system a type of planet distinct from the gas giants of jupiter and saturn that formed in the warmer region nearer to the sun we still understand relatively little about the formation of the ice giants beyond the very basic facts what we do know is that around 4.5 billion years ago as each of the planets was forming from the ingredients of the protoplanetary disk uranus found itself in a region where there was an abundance of water methane and ammonia at temperatures where these volatile compounds each with freezing points above 100k or minus 173 degrees celsius were cold enough to form the ices from which most of the planet would be built beyond this we can tell relatively little about the mechanism by which either uranus or neptune actually formed the detailed evidence and the computer models that have allowed us to tell the earliest beginnings of the solar system and revealed so much about the formation of the gas giants and the inner planets do not yet exist for the ice giants we simply lack a solid understanding of the mechanism by which these planets formed and much controversy remains around the details while there remain many mysteries out there in the darkness voyager did allow us to begin to piece together one of the most dramatic stories that unfolded after the formation of uranus as the craft spread past the planet's pale blue atmosphere it began to explore one of the least known gems in the solar system the rings surrounding this most distant of worlds unlike the shimmering rings of saturn these rings are so dark and faint that they're almost impossible to see from earth in fact we only discovered them by accident less than a decade before voyager arrived in the uranian system when in 1977 a team from the kuiper airborne observatory noticed a star that was briefly disappearing from view around the planet the conclusion they came to was that the star was being occluded by a ring system at first they confirmed five rings but they increased this number to nine after further observation voyager was able to image all nine of the rings in the system sending back extraordinary images of these dark delicate structures and also discovering two other faint rings in the process but as well as giving us our first detailed view of the rings voyager added to their mystery made up of a combination of boulders and dust the reflectivity of the substance of the rings as measured by voyager was found to be incredibly low the reason why these rings were so difficult to detect from earth was that unlike the glistening ice that dazzles in the rings of saturn the rings of uranus turned out to be grey and made of an extremely dark material making the spectral analysis of them extremely difficult if not impossible despite the spacecraft's close proximity we were unable to make any measurements of the constituents of the rings and over 30 years after our only close encounter we still don't know precisely what they're made of or where they came from our best guess is that they're made of ice and some other dark substance perhaps even organic compounds that have darkened over time the most likely scenario is that just as with the rings of saturn uranus is surrounded by the debris of a moon a world that once orbited her and that is now broken into the millions of fragments of the rings the rings are also extremely delicate and thin an ephemeral set of structures that appear to defy the laws of nature we would expect the particles to endlessly collide and the rings to spread out and begin to disperse over time a process that should be driven by the particles on the inside of the rings being drawn into the planet by its great mass but that doesn't seem to be happening something seems to be holding the rings in place hidden in the images taken by voyager 2 we found a surprising answer the outer ring epsilon is the brightest and densest of all the structures in the system and its width varies from 20 kilometers at its narrowest to just under 100 kilometers at its widest this fragile structure is also thought to be unimaginably thin we've never been able to measure its depth precisely but we think it could be little more than 150 meters deep maintaining this delicate structure in the hostile environment around the giant planet is the job of two tiny moons cordelia and ophelia whose existence was first discovered from images taken by voyager 2. with a radius of just 21 kilometers ophelia sits on the outside of the ring while the slightly smaller cordelia the innermost known moon of uranus sits on the inside of the epsilon ring together these two moons exert a profound influence on the structure and stability of the ring they embrace these shepherd moons quite literally guide the movement of objects around the edge of the ring helping to maintain the sharply defined border that we've seen so vividly from voyage's images simple orbital mechanics dictate that a moon or a ring particle that is orbiting close to the planet is moving more slowly than a moon or a ring particle that's orbiting further away which means that ophelia must be moving faster than the ring particles and cordelia more slowly that difference in speed is significant because if there's a particle in the epsilon ring that shifts for any reason maybe it has a collision loses a bit of energy starts to drop down then cordelia will tend to accelerate that particle back up into the ring again speeding it up by its gravitational influence whereas if there's a particle on the outer edge of the epsilon ring that gets a bit more energy and rises in altitude ophelia tends to slow it down and so it falls back into the ring again it's by this mechanism that these shepherd moons keep the ring neat and tidy and although voyager only discovered two such moons on its brief flyby of the system we can assume from the structure of the other rings that somewhere out there in the dark there are other hidden shepherds silently keeping order amongst the rocks and dust of their flock these two are just the beginning of uranus's system of satellites as of today we have discovered 27 moons around uranus all of which are named after characters from the works of shakespeare or alexander pope this tradition began in 1852 when john herschel the son of william discoverer of uranus named the first two moons after oberon and titania fairies from a midsummer night's dream the 27 moons are divided into three categories 13 inner moons including the two innermost cordelia and ophelia are all small dark bodies that are entwined within the ring system and may even share an origin with the substance of the rings then much further out lie nine irregular moons ranging in size from 120 to 200 kilometers in diameter these are almost certainly captured objects that have succumbed to the attraction of the planet's gravity in between this rabble of objects and inner moons we find the five major moons of uranus the only uranian satellites we knew of before voyager gave us a closer look the smallest of the set is the icemoon miranda a strange looking jagged world with a diameter of 470 kilometers it's one of the smallest objects we have studied in the solar system that has reached hydrostatic equilibrium or in other words is rounded by its own gravity to look at miranda is to see one of the most rugged landscapes in the solar system a world of extreme geological features carved into its icy surface and it's here that we find the highest cliff face verona rupays is reckoned to be 20 kilometers in height and it's been estimated that in miranda's low gravity it would take 12 minutes to fall from the top to the bottom of it the other four large moons around uranus are less visually striking all are thought to be constructed around a rocky core surrounded by a mantle of ice but these worlds are far from simple frozen lumps of rock they all show signs of having been geologically active at some stage in their distant past dark worlds in the distant solar system that have surfaces shaped by volcanism ariel has a bright and seemingly young surface paved over with recent and extensive flows of icy material in between the fault lines on its surface titania is also covered with huge geological faults and canyons suggesting this too was a tectonically active world at some time in its history with darker and potentially older looking features umbriel or oberon seem to be less active or certainly less active in recent times [Music] voyager 2 gave us our first chance to explore and understand the rings and moons of uranus but it was as the spacecraft widened its gaze that we were able to see in detail how this whole system is set in the most bizarre of orientations from our distant observations we had long thought that uranus spun on its side but to see the whole uranian system up close for the first time made it clear that something very different had happened in uranus's past to set it apart from every other planet uranus spins on its side with an axial tilt of 97.77 degrees resulting in one of its poles facing towards the sun at any one time the rings and moons are all orientated along this plane too so the whole system orbits the sun like a giant heavenly bullseye we don't know for certain why uranus is tipped over on its side but it seems likely that at some point in the distant past it was hit by another planet at least as large as the earth which quite literally knocked the planet over backed up by modern computer simulations it is entirely feasible that such an impact would cause the rest of the system to follow ending up with a planet its moons and rings corkscrewing around the sun the origin of uranus still remains for the most part unknown and the exact reason for this eccentric orientation remains one of the great mysteries of the solar system voyager 2 left us with as many questions as answers and when its encounter with uranus officially came to an end with the firing of its thrusters on the 25th of february 1986 we left the planet and its secrets behind thirty years later we still have no plans to return our first and only close encounter with uranus may have lasted for just a few hours but it returned thousands of precious images and data we had already gone further than ever before and as voyager left uranus behind it had ahead of it a lonely 1.6 billion kilometers before it would encounter another world it would take three more years before voyager 2 would reveal the first images of neptune the last planetary stop on its grand tour of the solar system from a distance of over 57 million kilometers our first images of this most distant of planets began to slowly come into view in early june 1989 with the near featureless orb of its sibling uranus still lingering in our thoughts the planet emerged from the darkness a tiny sphere with a thick blue hazy atmosphere and it was immediately apparent that this was the more animated of the two ice giants taking 246 minutes for signals from the spacecraft to reach the earth early images sent back to us across the vast distances revealed enormous bands of high altitude clouds floating above the blue haze this was no inert frozen world it was a planet of extremes you

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Published: Sat Jan 16 2021