Tag Archives: asteroids

What is the Oort cloud: the very edge of the solar system

Every system needs a boundary, and the Solar System is no different. Although we haven’t been able to physically reach and see it, we have a theory about what this edge looks like. And its name is the Oort cloud.

The hypothetical structure of the Oort cloud: an inner, disk-shaped cloud surrounded by a spherical outer structure. Image credits Pablo Carlos Budassi via Wikimedia.

Ask anyone on the street where the Solar System ends, and they’re likely to mention Pluto. To a certain extent, it wouldn’t be wrong; Pluto really is one of the farthest planets / dwarf planets from the Sun; as of early 2021, the farthest object in the Solar System is Farfarout . But if we want to be all sciency about it — and we do — the Solar System arguably ends where our star’s gravitational influence becomes too weak to capture and hold objects. In other words, it spans over all the space where the Sun is the dominating tidal force (Smoluchowski, Torbett, 1984). Exactly what constitutes the edge of the Solar System is still up to some debate, however, and some sources — including this post by NASA — consider the space beyond the heliosphere as being ‘interstellar space’.

For the purposes of this post, however, we’ll take the volume where the Sun’s gravity reigns supreme as being the Solar System. The point where that influence ends is far, far away from Earth. So far away, in fact, that we’ve never been able to actually see it, and, realistically speaking, there’s no way humanity will reach there while any of us reading this are still alive. But we do have some theories regarding what goes on out there.

The boundary of the Solar System is marked by a hypothetical structure known as the Oort cloud. We estimate that it is a truly vast expanse filled with varied clusters of ice, from innumerable tiny chunks up to a few billion planetesimals of around 20 kilometers (12 mi) in diameter. There are likely a few rocky or metallic asteroids here, as well, but not many in number. The material in the Oort cloud was likely drawn to its current position through the gravitational influence of the gas giants — Jupiter, Saturn, Neptune, and Uranus — in the early days of the Solar System.

All in all, it is one of the most exciting places humanity has not yet reached.

So what is it?

The thing to keep in mind here is that the Oort cloud is a hypothetical structure. We haven’t yet seen it, nor do we have any direct evidence of it being real. But its existence would fit with other elements and phenomena we see in the Solar System, and it does fit our theoretical understanding of the world around us, as well.

The Oort cloud is a vast body. Since it’s a theoretical structure, there’s quite a bit of uncertainty in our estimates of its size. Still, we believe it stretches from around 0.03 to 0.08 light-years from the Sun, although other estimates put its outer boundary at 0.8 light-years from the Sun. There are also estimates that place it between 1.58 and 3.16 light-years away from the Sun. Needless to say, we don’t have a good handle on exactly where it is, and how large it is.

“It is like a big, thick-walled bubble made of icy pieces of space debris the sizes of mountains and sometimes larger. The Oort Cloud might contain billions, or even trillions, of objects,” NASA explains.

But to give you a rough idea of the distances involved, however, we’ll use Voyager 1, the fastest-going probe we’ve ever sent to space, and the one currently farthest away from Earth. On its current course and acceleration, Voyager 1 would reach the Oort cloud in around 300 years; it would take it some 30,000 years to pass through the cloud (depending on its actual dimensions).

Voyager 1. Image credits NASA via Global Panorama / Flickr.

Still, don’t get too excited. None of the space probes humanity has launched so far will still be operational by the time they reach the Oort cloud; despite being powered by RTGs, a type of nuclear battery, all of these crafts will run out of power far before they reach the Oort clour.

Why do we think it’s a thing?

The concept of the Oort cloud was first suggested in the 1930s by Estonian astronomer Ernst Öpik. The idea was cemented in the 1950s when its existence was independently suggested a second time by Jan Oort, a Dutch astronomer. Because of this dual origin, it is sometimes referred to as the Öpik–Oort cloud.

The existence of this cloud was proposed mainly due to comets — long-period and Halley-type comets, to be precise. Since comets coming close to the Sun lose part of their volatile contents (for example water) under the influence of solar radiation, logic dictates that they must form away from the star. At the same time, gravitational influences would see them either collide with a planet or star or be ejected from the Solar System eventually — meaning that their ‘lifespan’ is limited. Since there are still comets zipping around the Sun, this means that there must be a reservoir of comets to be drawn towards our star.

Put together, both of these point to the existence of a cloud-like formation at the very edge of the Sun‘s gravitational influence populated with comet-like bodies — the Oort cloud.

Short-period comets orbit around the Sun every few hundreds of years; because of this short time, it’s generally accepted that they originate from structures closer to Earth, such as the Kuiper belt (a field of asteroids extending past Neptune). Long-period comets, however, can have orbits lasting thousands of years. The only source that could explain such huge spans of time is the Oort cloud. One exception to these rules is Halley-type comets. Although they are short-period comets, we believe they’re originally from the Oort cloud and that they’ve been pulled ever closer to the center of the Solar System under the gravitational effects of the Sun and inner planets.

What are we doing to study it?

The main impediment to our studying of the Oort cloud is distance. It’s simply too far away for our spaceships or probes to reach in any practical manner. There also haven’t been any direct observations of the Oort cloud.

Despite this, its existence is widely accepted in academic circles. Researchers rely on indirect methods of study to peer into the secrets of the Oort cloud. These revolve heavily around the study of comets and their properties. There is also a lot of effort being poured into developing devices and methods that can be used to spot individual bodies inside the Oort cloud. This is no easy feat, as they’re quite tiny by cosmological standards, and very far away.

Once we do have such tools at our disposal, however, astronomers will finally be able to confirm whether the Oort cloud actually exists. It’s very likely that it does, and it would fit with our current understanding of the Universe. But until we can see it, we won’t be able to tell for sure.

Jupiter.

Jupiter formed far from the sun and traveled closer during its early days

Jupiter traveled a bit in its youth, evidence from asteroids around the planet reveals. This brown gas giant formed four times as far away from the sun than the orbit it’s currently on and inched closer over the last 700,000 years.

Jupiter.

Jupiter and its moon Io.
Image via Pixabay.

New research led by members from the Lund University is revealing Jupiter’s wandering past based on the company it keeps. Using computer simulations to look at the distribution of near-Jupiter asteroids called Trojans, the team reports that their current layout in space can only be explained by Jupiter forming far away and then migrating to a closer orbit around the sun.

The prodigal son

“This is the first time we have proof that Jupiter was formed a long way from the sun and then migrated to its current orbit,” explains Simona Pirani, doctoral student in astronomy at Lund University, and the lead author of the study. “We found evidence of the migration in the Trojan asteroids orbiting close to Jupiter.”

Gas giants, as a rule of thumb, orbit pretty close to their host stars. To the best of our knowledge. that’s not where they form, however — these ponderous bodies of gas accrete further away and then migrate closer to the star.

In order to find out if Jupiter behaved the same way, Pirani’s team used computer simulations to estimate its movements over the past 4.5 billion years. The solar system was quite young in that day, its planets freshly-minted from the primordial dust which circled around the sun in a disk. At that time, 4.5 billion years ago, Jupiter was no larger than our own planet, the team reports.

It was also four times further away from the sun that it is now.

The Trojans Pirani talks about consist of two groups of thousands of asteroids that float around roughly on the same orbit as Jupiter — one group a bit in front and the other a bit behind the planet’s exact orbit. There are also 50% more Trojans in front of Jupiter rather than behind it, the team explains, a feature which helped them understand how the planet migrated over time.

“The asymmetry has always been a mystery in the solar system,” says Anders Johansen, professor of astronomy at Lund University and one of the paper’s co-authors.

We never really understood why there were more Trojans in front of Jupiter rather than behind it up to now. The team’s simulations suggest this happened because Jupiter gradually corralled in asteroids as it moved towards the sun. Based on the ratio between the two bodies of Trojans, the team says Jupiter likely formed four times farther out in the solar system than it is today. During its journey towards the sun, the planet’s gravity then drew in more Trojans in front of it than behind it.

According to their study, Jupiter’s migration took around 700,000 years, roughly 2-3 million years after it first started accreating. It moved closer to the center of the solar system on a spiral trajectory, as Jupiter orbited the sun in on increasingly tight orbit, goaded on by shifting gravitational forces from the gases surrounding the Sun, the team says.

The Trojans joined Jupiter while it was still a young planet — just a solid core without any atmosphere. This suggests that the Trojans are probably hewn of the same (or similar) matter that formed Jupiter’s core. NASA’s upcoming Lucy mission (scheduled for 2021) will allow the team a closer look at the Trojans.

“We can learn a lot about Jupiter’s core and formation from studying the Trojans,” says Anders Johansen.

The authors believe that the gas giant Saturn and ice giants Uranus and Neptune could have migrated in a similar way to Jupiter during their history.

The paper “Consequences of planetary migration on the minor bodies of the early solar system” has been published in the journal Astronomy & Astrophysics.

asteroid-belt

Main asteroid belt might be a dump for planetary leftovers, new theory proposes

A duo of French scientists at the Université de Bordeaux is proposing a radically different theory that explains the origin of the asteroid belt. According to their new model, the main asteroid belt that orbits between Mars and Jupiter could have formed from ejected material from various neighboring planets.

asteroid-belt

Credit: NASA.

The main asteroid belt is a circumstellar disc in the solar system that draws an imaginary frontier between the rocky and gas planets. It’s comprised of billions (perhaps trillions) of asteroids and minor planets which lie more than two-and-a-half times as far as Earth does from the Sun.

You’ll sometimes see Hollywood movies show a stressed commander trying to navigate his spaceship through dangerously close asteroids. Inside our solar system at least, that’s a non-issue, as the asteroids are spaced too far apart to warrant a close call. From Voyager to the more recent New Horizons mission to Pluto, none of our spacecraft had any issue crossing the asteroid belt. According to NASA, the total mass of the belt is less than the moon, far too small to weigh in as a planet.

A different take on the birth of the asteroid belt

The currently accepted theory that explains the belt’s formation suggests that early in solar system’s history, some five million years after the sun formed, Jupiter and Saturn moved inward toward the sun before changing direction and heading back to the outer solar system, scattering the asteroid belt in the process.

It’s thought that about 99 percent of the original asteroid belt is now gone, flung away by Jupiter’s massive gravitational pull. The gravitational effect is also thought to prevent the material from coalescing into a large planet.

Sean Raymond, the lead author of the study and an astronomer at the University of Bourdeaux, has a different take on the matter. He and colleague Andrei Izidoro propose a new, very different explanation for the asteroid belt’s formation. According to their calculations, it’s quite possible that the asteroid belt was initially almost empty, but was only later filled with S – and p-type asteroids, which form the inner and outer edges of the belt, respectively.

Asteroids closer to the rocky planets, the S-type, most frequently contain silicate, just like the inner planet. C-type asteroids tend to contain more carbon, similarly to the gas giants. This distribution suggests the material these asteroids are made of comes from early planets. Essentially, the asteroids could be excess material that was ejected into the asteroid belt where it remains to this day.

To test these assumptions, the researchers built a model of the early solar system where the space occupied by today’s asteroid belt is empty. Running the model forward revealed that it is indeed possible, though not necessarily likely, that material from the outer planets contributed the material required for the belt, the authors reported in Science Advances.

Raymond and colleagues are now seeing to improve their model on the lookout for more tangible evidence that supports their view.

"This rock is mine. Hands off!" Image: SLATE

How should space mining be regulated? Tough question, maybe for our future overlords to decide

At the Canadian Institute of Mining’s annual convention, NASA scientists said exploration and prospecting of celestial bodies like the moon or asteroids is decades away, but even so this shouldn’t stop regulations from being well established in advance. At the event, concerns were raised that ownership and management of resources in outer space are still far from being resolved.

Who owns stuff in space?

"This rock is mine. Hands off!" Image: SLATE

“This rock is mine. Hands off!” Image: SLATE

Joe Hinzer, a Canadian geologists, suggests mining in space could be modeled after mining on Earth, citing regulations currently in place set forth by an international committee under a United Nations umbrella.

“I think that’s the kind of approach that might work for extraterrestrial stuff as well,” he said.

Hinzer also cites the European Union as an example, which has its own dedicated legal framework and parliament. However, these are more geared toward sustainable mining through targeted initiatives and research funding. Mining in outer space is much more troublesome because there currently isn’t  (and hopefully never will be) any country that owns a piece of land on the moon or asteroid.

Over the years, some daring entrepreneurs announced publicly plans of mining asteroids. Some of these asteroids, by rough estimates, can contain more gold, platinum, cobalt, iridium, and many, many other precious or industrial metals than in the whole planet. One such venture is called Planetary Resources, and lists Google Chief Executive Larry Page, Google Executive Chairman Eric Schmidt, director James Cameron and entrepreneur Ross Perot Jr. as partners. Studies show that the moon has twenty times more titanium and platinum than anywhere on Earth, along with helium 3, a rare isotope of helium, which is nonexistent on our planet, that many feel could be the future of energy on Earth and in space.

Naveen Jain, co-founder and chairman of Moon Express, Inc., is one of the couple of billionaires today who share a common vision – the future of private space capitalization. Jain’s idea, in particular, is that of bringing lunar landers and mining platforms to the moon.

“People ask, why do we want to go back to the moon? Isn’t it just barren soil?” Jain said. “But the moon has never been explored from an entrepreneurial perspective.”

Besides trillions of dollars worth of precious metals and rare minerals, exploiting the moon and asteroids could set the stage for outer space outposts, crucial for refueling or scientific research; the kind that could really usher colonies on Mars, or Jupiter’s Europa. Of course, the technical requirements and challenges are immense. A vast, radiation-filled vacuum separates the space entrepreneurs from the space rocks of their ambitions, and any actual mining is many years away and might fail. John Gruener, a planetary scientist at NASA, doesn’t expect space prospecting to happen any time soon. At the  Canadian Institute of Mining convention he said in an interview:

“I see the real utilization of resources in space probably a couple of decades away — at the most optimistic.”

He did mention, however, that there are programs in development researching the possibility of sending robotic probes, maybe by the swarms, to test the feasibility of mining the moon.

“They can be accomplished in the near term, in five to 10 years,” Gruener added.

One of the focus of such a mission is ice water that’s already been discovered in lunar craters.

“The hope is we can separate the water from the other chemical constituents and then use the water to drink, use the oxygen to breathe and use the hydrogen and oxygen as rocket propellants,” he said.

Will entrepreneurs usher in a new space age, akin to how business exploited technology to improve our lives for better or worse? Challenges aside, the prospects of (inter)planetary economy growth are huge and considering we’re currently using up 1.5 Earths each year demands that we direct our ventures to other worlds, if humanity isn’t keen on quenching its greed at least.

Space law and loopholes

First and foremost, however, it’s not clear if any venture of this kind is legal. It’s not quite clear if it’s illegal either. The foundational document that governs doing stuff in space is the 1967 Outer Space Treaty, on which the United States, Russia, China, and more than 100 other countries are signatories. It’s one of the  five international treaties and agreements that govern activities in space as set forth by the  United Nations Office for Outer Space Affairs (UNOOSA), an international body tasked with establishing space laws and overseeing peaceful cooperation in space. The treaty specifically prohibits nations from deploying nuclear weapons in space or on celestial bodies, forbids claims to celestial real estate and reads that private space ventures are allowed.  Joanne Gabrynowicz, a space lawyer and editor emeritus of the Journal of Space Law at the University of Mississippi School of Law, says that things are peaceful and easy to enforce now because there’s yet no way to access those resources. Once the technology is in place, quarrels as to whom should have the right claim to these resources are bound to happen. With this in mind, it’s best to clarify space mining years before the necessary technology is introduced.

According to Gabrynowicz, “Non-state actors … are authorized to be in space, that’s what Article 6 of the Outer Space Treaty is all about. But we’ve just never reached agreement on what happens to extracted resources. … So what is happening is you have companies that are chomping at the bit to clarify the rules.”

In September last year, a House subcommittee discussed a new law that would explicitly give companies ownership over any materials they extract from an asteroid. Experts, however, disagree over whether such a bill would be compatible with international law. As always, the bill involves exploiting loopholes.

“Outer space, including the moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means,” reads the 1967 Outer Space Treaty.

Do you see something missing? Well, the treaty seems to be geared toward nations, but in theory it might not apply to private companies. At the same time, the treaty also specifies that countries are responsible for ensuring that private individuals and corporations within their borders abide by all the terms of the treaty. This means that the US would be forced not to allow Planetary Resource, for instance, to exert any claim of ownership or exploitation.

But there’s another provision in the document: “Outer space, including the moon and other celestial bodies, shall be free for exploration and use by all States.” Doesn’t mining fall under use? Some experts think so, and argue that any material extracted from celestial bodies belongs to the entity who performed the extraction. As an example, they cite the case of NASA which claimed ownership of 842 pounds of lunar rock collected during the Apollo missions. For now, it’s not clear whether the bill, called the Asteroids Act, will pass but it’s a first step in establishing some clear guidelines concerning space mining. Until then, no company will be prepared to shovel billions. It’s already risky, nevermind a potential lawsuit – no one would do it.

There’s no stopping “putting flags” on matter, whether it’s Antarctic ice, an island in the Pacific or the surface of the moon. Humans seem to have an innate sense for property. Mine, mine, mine. Even in outer space. Yeesh.

Three possible scenarios for the evolution of asteroid belts. Top: A Jupiter-size planet migrates through the belt, scattering material and inhibiting the formation of life on planets. Middle: A Jupiter-size planet moves slightly inward but is just outside the belt (this is the model proposed for our solar system). Bottom: A large planet does not migrate at all, creating a massive asteroid belt. Material from the hefty asteroid belt would bombard planets, possibly preventing life from evolving.

Asteroid belts may be crucial to intelligent life formation – alien life could be rarer than thought

When you think of asteroid impacts, the last thing that might come to mind is life. Contrary to popular belief, a team of researchers have recently presented their theory that holds intelligent life on our planet spurred with the help of asteroid impacts. As cosmic cold rock hit Earth, the impacts allowed for a shift in environment that pressured life to adapt and make rapid changes. Also, during the planet’s early days, frozen water, which came along with asteroids, might have had a crucial role in birthing life.

Asteroids aren’t enough though. For intelligent life to foster on an exoplanet, these space rocks need to be in a certain position, according the hypothesis formulated by astronomers Rebecca Martin of the University of Colorado in Boulder and Mario Livio of the Space Telescope Institute in Baltimore. Out solar system’s asteroid belt – between Jupiter and Mars – is not an accident,  according to the researchers, and was indispensable for life formation.

Alien life needs just the right asteroid belt

The researchers claim that for a planet to harbor alien life, chances are that it needs an asteroid belt of its own, similar to that of our solar system, positioned in the so-called “snow line”. At this certain orbit, frozen materials like water ice will remain in this state; any closer to the sun will melt them, and any farther would lead to the asteroids being gobbled by the gravitational pull of some giant planet, like Jupiter in our case.

“To have such ideal conditions you need a giant planet like Jupiter that is just outside the asteroid belt [and] that migrated a little bit, but not through the belt” Space Telescope Science Institute astronomer Mario Livio said. ”If a large planet like Jupiter migrates through the belt, it would scatter the material. If, on the other hand, a large planet did not migrate at all, that, too, is not good because the asteroid belt would be too massive. There would be so much bombardment from asteroids that life may never evolve.”

Three possible scenarios for the evolution of asteroid belts. Top: A Jupiter-size planet migrates through the belt, scattering material and inhibiting the formation of life on planets. Middle: A Jupiter-size planet moves slightly inward but is just outside the belt (this is the model proposed for our solar system). Bottom: A large planet does not migrate at all, creating a massive asteroid belt. Material from the hefty asteroid belt would bombard planets, possibly preventing life from evolving.

Three possible scenarios for the evolution of asteroid belts. Top: A Jupiter-size planet migrates through the belt, scattering material and inhibiting the formation of life on planets. Middle: A Jupiter-size planet moves slightly inward but is just outside the belt (this is the model proposed for our solar system). Bottom: A large planet does not migrate at all, creating a massive asteroid belt. Material from the hefty asteroid belt would bombard planets, possibly preventing life from evolving. (C) NASA

The scientists analyzed data from NASA’s Spitzer telescope, which has so far found infrared signals around 90 different stars which can indicate the presence of an asteroid belt. Of the 520 gas giants found orbiting other stars, in only 19 cases were they outside of where that star’s snow line would be expected to be. This suggests that fewer than four percent of exoplanet systems will be equipped to support the evolution of advanced, intelligent life in accordance with the punctuated equilibrium theory.

Their research isn’t a bash at alien life research, but on the contrary. It suggests hints and gives a pertinent starting point for scientists to better channel their efforts, and have a better chance at getting results.

“Our study shows that only a tiny fraction of planetary systems observed to date seem to have giant planets in the right location to produce an asteroid belt of the appropriate size, offering the potential for life on a nearby rocky planet. Our study suggests that our Solar System may be rather special,” said Martin.

Findings were presented in the Monthly Notices of the Royal Astronomical Society. 

TD54 Asteroid Collision Causes Atom Bomb-like Effects

Tuesday at 6:51 a.m. EDT (1051 GMT) a small asteroid dubbed TD54 passed the Earth dangerously close, above a section of Southeast Asia by Singapore, being at its closest 28,000 miles from our blue planet. The asteroid, 2010 TD54 was first discovered on October 9th, by scientists in Arizona at a NASA-sponsored lab. A few days after being spotted, the asteroid collided with another similar asteroid blasting in a spectacle of colored dust and energy equal to a small atom bomb. A low-quality photo of the event can be seen above surprised by a telescope. Scientists are calling the collision “peculiar,” given that “X” shape you can see in the left side of the shot, at the beginning of the trail of debris.

If you found the distance TD54 flew past Earth frightening, know that it was relatively small, sized at a mere 33 feet, enough to be melted away upon atmospheric entry. NASA regularly tracks asteroids and comets that fly near Earth as part of its Near-Earth Object Observations program, which uses a network of ground and space telescopes. The program has tracked 85 percent of the largest asteroids that fly near Earth and 15 percent of asteroids in the 460-foot class, according to the latest report. [via MSNBC]