Kuiper Belt: The Mystery Of The Missing Planets

Kuiper Belt: the mystery of the missing planets A little mystery, coupled with a great  disappointment, surrounded the early years of this century in the search for new planets  in the region of the solar system known as the "Kuiper Belt." This search led to the discovery  of several large asteroids or planetoids. Anyone who followed the events of those years  will also recall that after a period of exciting discoveries, culminating in 2003 with the finding  of the significant Eris – even hailed

at the time as "the tenth planet" – the flow of good news  from the Kuiper Belt almost suddenly ceased. Since then, only routine discoveries  and no new Eris on the horizon... This, despite the discoverers expressing  optimism earlier about the possibility that this remote region could host dozens  of other objects the size of Eris and Pluto. Could it be that the Kuiper Belt mine had  already exhausted its best pieces? Or perhaps, more simply, had people grown tired of  searching? Or was there

something else? The suspicion lingers... So, what if  we tried to uncover the truth together with the help of this super interesting video? Are you up for it? Great, let's get started then! OK, But not so fast! First, we  need to say something more about the remote region at the center of  the whole story... the Kuiper Belt! When we think of the solar system, rocky  planets like Earth, gas giants like Jupiter, natural satellites like the Moon, and  asteroids orbiting between Mars and Jupiter com

e to mind. However, the solar  system doesn't end there. Beyond Neptune, the farthest planet from the Sun, extends a vast  region populated by millions of icy objects, which are probably remnants of the  material used to build the solar system. This region is called the  Kuiper Belt, named after the Dutch-American astronomer Gerard Kuiper,  who hypothesized its existence in 1951, building on studies conducted a decade earlier by  the Irish astronomer Kenneth Edgeworth. In fact, it would be more

accurate to call  it the Edgeworth-Kuiper Belt. The belt is located at a distance from the Sun  ranging from 30 to 50 astronomical units (AU), where 1 AU is the average distance between  Earth and the Sun, about 150 million kilometers. It contains at least 100,000  objects with a diameter exceeding 100 km, although many more are believed to  exist—too small or faint to be detected. The most famous of these objects is,  of course, Pluto, the dwarf planet that was considered the ninth planet of  t

he solar system until 2006. But Pluto is not alone. In the last twenty years, thanks  to technological advancements in telescopes, many other objects of similar size to Pluto  (2450 km in diameter) have been discovered: objects like Eris (2326 km), Makemake (1430),  Haumea (1595), Quaoar (1086), and others, all with a diameter exceeding 1000 km. These objects are called KBOs, an acronym for Kuiper Belt Objects, and they  vary greatly in shape, size, color, composition, and orbit. Some are round,

others elongated,  and still others irregular. Some are red, others gray, and some are white. Some are  made of water ice, others of methane ice, and still others of nitrogen ice. Some orbit  near the plane of the ecliptic, while others have highly inclined or eccentric orbits. Some have  one or more satellites, while others are solitary. In essence, KBOs are genuine worlds that tell  us the story of the solar system and challenge us to explore and understand them better.  The Kuiper Belt is th

e true frontier of the solar system and represents a significant  opportunity for science and adventure. However, this frontier bears little resemblance  to the solar system as we know it. The American astronomer Fred Whipple once said that if we  want to continue considering the solar system according to the familiar representation  still used in many educational materials, with the Sun at the center of a system  of ordered ellipses, it becomes really challenging to include the remote, chaotic,

  and mysterious regions beyond Neptune. If we instead strive to see it as a complex  and continuously interacting physical system, with the Sun at the center of a vast sphere  of influence extending tens of thousands of astronomical units away, populated by a myriad  of exotic objects and only a small minority of familiar objects located in its immediate  vicinity (the known planets and satellites), then our vision of the system changes profoundly. Until thirty years ago, the existence of the O

ort  Cloud, as well as that of the closer Kuiper Belt, were only working hypotheses. Until the  early years of this century, the region beyond Neptune and Pluto seemed inhabited only  by a sparse representation of normal asteroids. Credit for the past hypotheses of the "something  that wasn't there yet" goes to visionaries like Kenneth Edgeworth and Gerard Kuiper. However,  it's the astronomer Michael Brown, a professor of planetary astronomy at the California  Institute of Technology, who deser

ves credit for contributing in recent years to filling  those distant regions with real objects. However, and here's where we get into the  topic, it was only from 2002 to 2007 that things truly started to get serious. Almost  always in collaboration with Chad Trujillo, the discoverer in 1992 of the first  object found in the Kuiper Belt, Brown, during those years, unleashed the imagination of  astronomers and enthusiasts alike by populating those regions with objects of almost planetary  dimens

ions, including the largest of them all, Eris, much more massive than Pluto itself. "Those were formidable years," one might say! But from 2007 onwards, it seemed that the exciting  series of discoveries had suddenly come to a halt, just when there was hope for the discovery of  something even more sensational... To some, it almost seemed like the Prague Conference  in 2006, which had decreed Pluto's demotion from the rank of the planet, put an end to  the discoveries, demotivating researchers a

nd effectively transforming the search for  new planets into the less fascinating and lucrative "search for dwarf planets." The last major KBO, Gonggong (1230 km in diameter), was discovered in 2007.  Since then, only routine discoveries and no new Eris on the horizon... The question at this point is: did things really go as rumored? Was  there a slowdown on the researchers' part? "Before moving on, don't forget to subscribe  to our channel if you haven't already... make sure to hit the notifica

tion bell so  you don't miss out on our daily videos!" Well, not exactly, and Brown himself explains  it. In practice, Brown states that the ability to find all those objects in such a short time  was certainly not the result of chance but of observational survey methods that had covered both  the northern and southern celestial hemispheres, leaving only the region of the galactic  plane and the ecliptic poles unexplored. It was certainly possible, as Brown reports,  that some particularly brigh

t KBOs might have escaped detection, but numerous statistical  studies indicated that observational campaigns had an efficiency rate between 70% and  90%. This led to the belief that the large KBOs yet to be found must be very few. At that point, it was decided that organizing a survey to cover the missing areas would be too  costly for the expected results, and it was only for this reason that the discoveries seemed to  abruptly cease. In other words, it was not deemed useful to initiate new re

search programs. Furthermore, the fact that all the major KBOs identified up to that point could be  traced back even in old archival images led researchers and Michael Brown to believe that,  instead of starting new observational programs, they could systematically exploit the  existence of already established archives. An ideal dataset was immediately identified  in the one created by the Catalina Sky Survey, an American project that uses three telescopes  to discover and monitor the so-called

Near-Earth Objects (NEOs). Two of these instruments (1.5  and 0.7 meters in diameter) are located in Arizona, while the third (0.5 meters) is in  Australia at the Siding Spring Observatory, where it contributed to the Siding Spring  Survey in the southern celestial hemisphere. As we know, NEOs are asteroids, comets,  and meteoroids that can pose an impact risk to our planet, and that's the reason  justifying a dedicated project to scour the sky inch by inch to discover them. Brown and company w

ere not interested in NEOs at all but only in the images produced by  the Catalina Sky Survey over years of continuous research. Those images were perfect for their  purposes: the survey had covered a whopping 19,700 square degrees of the sky (remember that  the entire celestial sphere is formed by 41,253 square degrees) between a declination of -25°  to +70°. Meanwhile, the Siding Spring Survey had archived 14,100 square degrees from -80° to  0°. Taking into account the overlapping areas, the o

verall useful coverage was about 30,000  square degrees, three-quarters of the entire sky! The limiting magnitude for the  two surveys was +19.4 and +18.9, respectively, sufficient to allow the  detection of large objects in the Kuiper Belt. Each observation area had been captured  several times over 7 years, from 2005 to 2012. At that point, they had to figure out how  to proceed. It had been calculated that in those 30 thousand square degrees of the sky,  approximately 3.9 billion transient ev

ents should have been photographed (about 130 thousand  per square degree!). For "transient event," we mean a dot of light on the plate that does  not correspond to any known object but can be anything: a supernova, a flare, an artifact, a  main-belt asteroid, a small NEO, a cosmic ray... How to distinguish a real KBO,  then, from everything else? As one can imagine, this was neither easy nor  immediate, but to begin with, using a digital "blink comparator," all those dots that persist  without

showing the slightest movement over time can be eliminated... Moreover, we know  that a KBO, on average more than 25 AU away, cannot exhibit proper motion higher than 4.9  arcseconds per hour under any conditions. Anything moving faster (NEOs, main belt asteroids,  pairs of artifacts, etc.) is therefore discarded. Well, even after this double selection, there  were still a lot of dots left: 3.5 million! At this point, the so-called "Keplerian filter"  comes to the rescue. All the dots that night

after night seem to indicate the movement of an  object are examined by software that, each time, asks the question: does this sequence  of dots meet the criteria of an object moving in a Keplerian orbit? If the answer is  reasonably positive within preset limits, and if the magnitude does not show suspicious jumps,  then the case is classified as a "probable KBO." At the end of the entire process, complicated also  by the application of more complex "identification or removal" algorithms, Brow

n and his team  found themselves dealing with 1192 "probable KBOs" in the northern hemisphere and 5515 in the  southern hemisphere. A sufficiently small number (obviously, many of these cases were the result of  multiple observations related to the same object) to allow the evaluation of each individual entry. And that's how the initial dense daisy remained with only eight petals.... This, metaphorically speaking, meant that thanks to the Catalina Survey, Brown  and colleagues had successfully i

dentified the existence of eight large planetary  objects belonging to the Kuiper Belt! Experiment successful, then? Well, not  exactly... It's almost funny to say, but the eight KBOs that survived the screening  were objects discovered and cataloged many years ago, and almost all found by Brown himself! Read their names, and you'll understand right away: Makemake, Eris, Orcus, Haumea, and...  even Nereid (yes, Neptune's small moon!)... In practice, neglecting the almost humorous  side of things

, we can summarize the whole story like this: the analysis of the Catalina  Survey had widely achieved its goal and had proven so valid that it had detected with 100%  efficiency the presence of all those KBOs that, during the years when the archive was being  formed, were below the instrumental limiting magnitude (except Pluto, which during that  period was immersed in the Milky Way, and Quaoar, located at the limit of an uncovered region)! And the fact that the survey did not highlight the exi

stence of even one entirely new KBO  can mean only one thing: Below that magnitude, there's nothing left to discover! Or at least, very little. In reality, in the article, Brown leaves some hope, in  the sense that, as we mentioned earlier, the Catalina survey left the regions  around the ecliptic pole uncovered, corresponding to about 20% of the total sky. This,  added to the faint possibility that something might move in the unexplored (and unexploitable)  areas occupied by the galactic plane,

leads the American astronomer to calculate a 32% probability  that there is still a large KBO to be discovered and a 10% probability that there are two. Can we be at peace, then? Have we already found all the dwarf planets in the solar system?  The answer is no, for at least two good reasons. The first is in the small door left open by the  incomplete coverage of the survey (remember that even Eris has an orbit strongly inclined to the  ecliptic, which allows us to hope that the regions north o

f the ecliptic might still hold surprises),  while the second reason is that we have not searched everywhere. The so-called Oort Cloud  remains to be explored, or at least, its inner part, where numerous simulations suggest the  existence of planets the size of Mars or Earth. Due to their distance from the Sun, however,  these still hypothetical objects are too faint to be discovered with current technologies. We'll have to be patient or hope for that 32% calculated by Brown. Nevertheless, it is

quite a challenging task that will require all the  observational power of next-generation telescopes, from both ground and space, such as the James  Webb or the Extremely Large Telescope, a 39-meter telescope from the ESO under construction  in the Atacama Desert in Chile. In fact, it is precisely from the latter - which will be  ready in 2026 and will photograph the sky reaching mag. +29 - that we expect the biggest news. So, let's be patient, a few more years, and no planet or planetoid will

be able  to escape us. No matter where it hides!