My latest book, entitled “Darker Stars” is now available in paperback. The book’s sub-title is “New Evidence: The Scope of Our Growing Solar System, Planet X, Invisible Planetoids, Gas Giants, Comets, Planet Nine, and More…”. Here is the description on the back cover:
“Darker Stars explores the often contentious subject of Planet X. Building upon the historically hot-and-cold hunt for an additional planet in our solar system, the author examines the recent resurgence of scientific interest in this subject, in the re-branded form of Planet Nine. The elusive nature of this object provides the impetus for a hypothesis about planet building in interstellar space, and associated phenomena. In particular, free-floating planetary mass objects and sub-brown dwarfs exemplify the anomalous new characters shaking the foundation of the classic star/planet boundary.
“Our solar system, too, is full of anomalies, strongly implying the presence of another massive planetary body. As our understanding of dark bodies in interstellar space builds, the author argues whether the existence of Planet X-type bodies should now be considered the new norm. With over 100 images and sources, approximately 500 references, and an extensive index, Darker Stars provides a robust and scientifically-based study of the re-fashioned outer solar system.”
The book is 376 pages long, and is published by Timeless Voyager Press in a 6″x9″ paperback format, available through Amazon. There is a vast amount of information about the mysteries of the outer solar system within the book. The book also discusses recent advances in understanding about the outer solar system, and hypotheses about Planet X and its re-branded corollary Planet Nine. I present a new hypothesis about how planets might evolve over time in interstellar space, and how this process may explain why Planet X has been so difficult to observe directly. Why assume objects beyond Neptune form the same way as those within? Drag and solar wind effects on dust will be different, even more so in interstellar space beyond heliosphere. New rules are needed for the outer solar system. #darkerstars
‘Darker Stars’ brings together a decade of Dark Star blogs and articles, updated with brand new material, and then completely re-written into a comprehensive and fully-referenced non-fiction book. It is both robust and challenging in its approach.
Chapter 1 The Incomplete Solar System
Chapter 2 The History of Planet X
Chapter 3 Sub-Brown Dwarfs in the Infrared
Chapter 4 The Extended Scattered Disk
Chapter 5 Re-Branding Planets
Chapter 6 The Hunt for Planet Nine
Chapter 7 Arguments Against Planet Nine
Chapter 8 Planet Nine and the Nice Model
Chapter 9 Further Planet X Evidence Among The Minor Bodies
Chapter 10 The Origins of Planet X
Chapter 11 Building Planets in Interstellar Space
Chapter 12 The Shroud Hypothesis
Chapter 13 An Abundance of Dark Stars
Chapter 14 ‘Oumuamua
Chapter 15 Jovian Mysteries
Chapter 16 Puzzling Pluto
Chapter 17 Meandering Mars
Chapter 18 Water World
Chapter 19 Moon Mysteries
Chapter 20 Comets and Asteroids
Chapter 21 Nibiru
Chapter 22 The Dark Star Revisited
The new paperback book is available from Barnes and Noble:
It is also available from many other reputable booksellers online. including Amazon:.
Signed and dedicated copies of the book can be obtained directly from me: I’m based in England, so bear in mind the likely postal costs for what is quite a substantial book!
There is no doubt that the scientific advocacy for a Planet X body has been significantly strengthened by the work of Brown and Batygin, who published their first paper about ‘Planet Nine’ three years ago (1). Mike Brown is a renowned astronomer in academic circles, whose speciality is hunting down distant Kuiper Belt Objects and dwarf planets in the outer solar system.
Following on from the work of Trujillo and Sheppard (2), he and his Caltech colleague Konstantin Batygin studied odd similarities in the orbits of distant scattered disk objects (SDOs) which lie beyond the regular Kuiper belt. Certain orbital properties of these eschewed objects seemed to be gathered into place within a common clustering, and the astrophysicists determined that something massive located well beyond them must have been responsible for shepherding these objects into such a serendipitous arrangement. They advocated a renewed search for Planet X, which had been confined to the doldrums of astronomy for decades, and re-branded the object ‘Planet Nine’ (3).
Planet Nine is thought to be a super-Earth object, upwards of 10 Earth masses. Searches for exoplanets have determined that such planets are common enough elsewhere, but, so far as we know, absent from our own shores within this solar system. Planet Nine is likely twenty times further away from us than Pluto, maybe more, and how such an object could have ended up so far away from the rest of the planets has vexed scientists. Of course, it remains hypothetical, because, despite the observational strength of modern day astronomy, Planet Nine has not been located. Its position is unknown (beyond ruling out certain sections of the sky), as its existence can only be inferred from the clustering data, but not determined directly from it.
Despite its 3-year long ‘no-show’, Brown and Batygin stand by their initial paper, and have published a follow-up paper this month to continue to argue their case (4). It primarily responds to the arguments raised by scientists working for the Outer Solar System Origins Survey (OSSOS) who found similar objects which did not seem to belong to the P9 cluster (5), and who went on to argue that the evidence for Planet Nine should be dismissed due to inherent observational bias in the data (6). At the time, Batygin quickly refuted that criticism, finding more patterns in the outer solar system snow, although I wondered whether the OSSOS data may be opening up another issue entirely about Planet Nine’s argued-for position (7). Anyway, Brown and Batygin’s new paper presents their subsequent work about the issue of observational bias, and offers a robust analysis leading to following conclusion:
“From this now more complete understanding of the biases, we calculate that the probability that these distant KBOs would be clustered as strongly as observed in both longitude of perihelion and in orbital pole position is only 0.2%. While explanations other than Planet Nine may someday be found, the statistical significance of this clustering is now difficult to discount.” (4)
Having rebutted their critics on one front, the Caltech team face another problem this month, this time in the form of an alternative explanation for the clustering anomalies proposed by researchers from the University of Cambridge. This new hypothesis involves the possible existence of a very significant disk of objects beyond the Kuiper belt, with a combined mass of 10 Earth masses, or perhaps less.
This massive ring of material would be eccentrically inclined to the invariant plane of the planets. The astrophysicists’ calculations and simulations show that such a massive eccentric disk might have the gravitational pull to create the observed clustering of extreme SDOs (8), but the mass required represents a couple of orders of magnitude of mass greater than the known Kuiper belt. Arguing that studies of other young star systems show extended debris disks, the authors seem quietly confident about the potential existence of such a massive extended disk:
““If you remove planet nine from the model and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs,” said [Antranik] Sefilian, who is a Gates Cambridge Scholar and a member of Darwin College.” (9)
Brown points out that it’s unusual in science for a new hypothesis – in this case the proposed existence of Planet Nine to explain the observed clustering of SDOs – to not face a barrage of counter-hypotheses. For some reason, all of the attention up until this point has been focussed upon the statistical credibility of the cluster properties. Brown acknowledges the new Cambridge paper is the first stab at an alternative explanation for the extended SDO cluster (11). In fact, a similar explanation has already been offered within academic circles, by a group based in Colorado led by Ann Marie Madigan last summer. The Colorado group argued that a significant amassed collection of distant asteroids could explain the observed anomalies (10). Mike Brown explains the difference between these two papers: “…although the hypotheses sound similar, they are really totally unrelated. The one from last summer doesn’t actually explain…what we see. This one, at least, does.” (12)
Despite actually offering what appears to be a mathematically credible explanation, Brown is sceptical of the new Cambridge paper on a couple of fronts: (1) The required mass of the disk (as above), and (2) its provenance (11). How could such a warped extended disk have been shaped in the first place? This raises another vexed question about how such a weird disk came to be, which flies in the face of the Cambridge authors’ claim to have provided a simpler explanation than Planet Nine.
It is known that the invariant plane of the planets is warped away from the solar equatorial plane by about 6-7 degrees. Planet Nine, on the other hand, is likely to be inclined by about 30 degrees, and may itself represent an explanation for this warping, should its mass be significant enough to have shaped the rest of the solar system in this way. One of the several strands of evidence pointing towards the existence of a Planet Nine/X body is the ~6 degree tilt of the invariant plane of the planets away from the Sun’s own equatorial plane. In other words, like the Earth, the Sun’s axis is tilted away from the plane of the planets.
All things being equal, the Sun and the planets should have formed out of a common rotating disk of primordial matter – the coalescing pre-solar nebula. It’s understandable that many of the planets engaged in a bit of to-and-fro during the early period of planet-forming, and so ended up a little skewed. But the Sun is the dominant player, and it should take a considerable gravitational influence to draw the planets away from its own equatorial plane. Yet, the Sun is seemingly a lonely star. So, that pesky 6 degree tilt has to be explained by something. Maybe a passing star pulling at the planets at some point in the past; or maybe the Sun had an early companion (within its birthing dense core) which affected the system’s alignment; or maybe another significant planet strongly inclined to the ecliptic, influencing the others over time (13).
Studies of protoplanetary disks in young star systems is revealing similar warps elsewhere. The latest case concerns a very young single protostar system known as L1527. This system is so young that there is an implication that the warping may be occurring in the primordial cloud itself (14). The disk in question is effectively in two parts, where the warping issue affects the inner disc out to some 40-60 AU from the star (15). In the perceived absence of a companion object causing this effect, it is thought that the gravitational effect of the cloud itself is causing the warp in the protoplanetary disk.
But here’s the thing: Just because there isn’t a self-evident, luminous companion object near to L1527, doesn’t mean that there isn’t a darker companion lurking around somewhere nearby, tugging at the disk. It has been suggested that all stars begin life within dense cores, containing at least two protostars (16). In turn, this has implications about the potential for failed stars being ubiquitous companion objects (17). So, maybe L1527 does have an unseen sub-stellar companion affecting the structure of its inner disk.
Another item of interest to add is news about another misaligned disk, this time around a young binary star system (19). In this case, the disk orbits at right angles to the orbit of the two stars which make up the binary HD 98800, meaning that the disk is in a perpendicular polar misalignment (19). Furthermore, the authors state that despite the extreme misalignment, the disk itself has physical properties similar to those around single stars, including, therefore, potential planet forming conditions.
So it is clear that such warped arrangements are by no means confined to the solar system, can be pretty extreme, and can appear very early on in the lifetime of a star system. What’s less clear is why they arise in the case of sible star system, seemingly minding their own business. Some kind of distant, dark companion object pulling at the rest of the system seems a reasonable enough explanation – one that was already present, or co-forming, within the stellar birth cluster. Perhaps that might be a body the size of Planet Nine (a proposed super-Earth), perhaps something bigger still.
So, happy third birthday, Planet Nine! You may still be a mere twinkling in a Californian astronomer’s eye, but you’ve already evoked a modern renaissance in the history of Planet X.
Written by Andy Lloyd, 24th January 2019
1) K. Batygin & M. Brown “Evidence for a Distant Giant Planet in the Solar System” The Astronomical Journal, 20 January 2016, 151(2)
2) Chad Trujillo & Scott Sheppard “A Sedna-like body with a perihelion of 80 astronomical units” Nature, 27 March 2014, 507: 471-474, http://www.nature.com/nature/journal/v507/n7493/full/nature13156.html
3) Andy Lloyd “Massive Planet X Now Urgently Sought by Top Planet-Hunters” 20-23 January 2016, http://www.andylloyd.org/darkstarblog34.htm
4) Michael Brown and Konstantin Batygin “Orbital Clustering in the Distant Solar System” The Astronomical Journal, 22 January 2019, 157(2)
5) Cory Shankman et al. “OSSOS VI. Striking Biases in the detection of large semimajor axis Trans-Neptunian Objects”, 19th June 2017, The Astronomical Journal, 14 July 2017, 154(2)
6) Josh Sokol “New haul of distant worlds casts doubt on Planet Nine”, 21st June 2017 http://www.sciencemag.org/news/2017/06/new-haul-distant-worlds-casts-doubt-planet-nine
7) Andy Lloyd “Planet Nine: Are They Digging in the Wrong Place?” 3 July 2017 http://andy-lloyd.com/planet-nine-digging-wrong-place/
8) Antranik Sefilian and Jihad Touma. ‘Shepherding in a self-gravitating disk of trans-Neptunian objects.’ The Astronomical Journal 21 January 2019, 157(2) https://iopscience.iop.org/article/10.3847/1538-3881/aaf0fc/pdf
9) Sarah Collins “Mystery orbits in outermost reaches of solar system not caused by ‘Planet Nine’, say researchers” 21 January 2019 https://www.cam.ac.uk/research/news/mystery-orbits-in-outermost-reaches-of-solar-system-not-caused-by-planet-nine-say-researchers
10) Daniel Strain “Collective gravity, not Planet Nine, may explain the orbits of ‘detached objects'” 4 June 2018 https://www.colorado.edu/today/2018/06/04/collective-gravity
11) Mike Brown “Is Planet Nine just a ring of icy bodies?” 22 January 2019 http://www.findplanetnine.com/
12) @plutokiller replying to @darkstarandy, 24/1/19
13) Andy Lloyd “Does Planet Nine Solve the Riddle of the Sun’s Obliquity?” 30th July 2016 http://andy-lloyd.com/planet-nine-solve-riddle-suns-obliquity/
14) RIKEN Press Release “Early protostar already has a warped disk” 1 January 2019, http://www.riken.jp/en/pr/press/2019/20190101_1/
15) Nami Sakai et al. “A warped disk around an infant protostar” Nature, 31 December 2018, https://www.nature.com/articles/s41586-018-0819-2
16) Sarah Sadavoy & Steven Stahler “Embedded Binaries and Their Dense Cores” MNRAS, 21 August 2017, 469(4): pp3881–3900
17) Andy Lloyd “The Sun was Born with a Companion” 15 June 2017 http://www.andylloyd.org/darkstarblog51.htm
18) Peter Thorley “Double star system flips planet-forming disk into pole position” 14 January 2019 https://warwick.ac.uk/newsandevents/pressreleases/double_star_system/
19) Grant Kennedy et al. “A circumbinary protoplanetary disc in a polar configuration” 15 january 2019 Nature Astronomy Letters, https://www.nature.com/articles/s41550-018-0667-x.epdf with thanks to Lee
We’re used to thinking about small asteroid-like bodies emitting gaseous tails: They’re called comets. But could there be such things as cometary planets? Two studies regarding the escaping atmospheres of hot exoplanets have been published this month in the journal Science (1,2). The first is a transiting warm Neptune-mass exoplanet located 20 times nearer its host star than the Earth is to the Sun. The tail of helium being blasted away from this planet by radiation from its orange dwarf host star extends some five planetary radii out. The planet, known as HAT-P-11b, is blown up like a helium balloon, according to the researchers who have been studying it (3).
However, HAT-P-11 is not a young star still blasting away at the primordial atmosphere of a new Neptune-sized world, as you might expect. Instead, HAT-P-11 is 6.5 billion years old; almost 2 billion years old than our own Sun. So, why is it still managing to have such a devastating effect upon the Neptune-sized exoplanet in its midst? Common sense would dictate that you can’t have such an effect going on for 6.5 billion years, as the planet would have been eradicated long ago. Loosely bound helium held in this gaseous ‘envelope’ would surely leak out into space in considerable quantities over time? Like with comets repeatedly transiting around their stars at perihelion, you would think that at some point the volatile gases would all get blown away. Perhaps HAT-P-11b was once a much greater hot Jupiter world which has shrunk to Neptune proportions over time. Or, perhaps this is a case of inwards migration of this world from further out in the star system.
A similar tail of atmospheric helium is being blasted back from another giant exoplanet, this time known as WASP-69b (5). This world is about a quarter of the mass of Jupiter, making it a sub-‘hot Jupiter’ object. The discovery of this helium tail was also made using the Carmenes instrument, installed on the 3.5-meter telescope of the Calar Alto Observatory in Spain. In this case, the host star, is 2 billion years old and just a little smaller than our own Sun (6), making it another orange dwarf. So, again, this effect isn’t due to the young nature of the system – there is a sustained effect taking place over a long period of time if the system has been static for that entire time. How long can such helium leakage be sustained from this ‘evaporating exoplanet’? Previous discoveries of such leaking exoplanets have included a ‘hot Neptune’ planet whizzing around a ~9 billion year old red dwarf, Gliese 436 (7). Read More…
One of the essential ingredients of planet-building is the clumping of dust in space. Planets can build up through the gravitational attraction of objects in space which are already about 1000km across. The problem is how do these proto-planetessimals get built? The mechanism for how dust clumps together has not been well understood. After all, when materials moving at speed through space collide, they may break apart in the force of the impact, showering down collisional cascades of ever small materials – the exact opposite of planetessimal-building. Somehow, dust must clump together into grains, which then join forces to create space pebbles, then boulders, then mountains, etc.
For these materials to adhere together, an inherent stickiness may be needed, aided by the presence of greasy organic compounds (in the form of aliphatic carbon). While it is recognised that this greasy component is more readily available in interstellar space than previously suspected (1), does that adhesive property extend down to space dust? If not, what mechanism could be bringing together ever larger clumps of plain old granular dust in space?
New research work suggests that dust and gas are not happy bedfellows within a magnetic field. So, rather like oil in water, dust particles seem to come together within gas as the mixture traverses the galactic tides. Indeed, any force brought to bear on dust moving through gas seems to create this clumping effect:
“… it was previously assumed that dust was stable in gas, meaning the dust grains would ride along with gas without much happening, or they would settle out of the gas if the particles were big enough, as is the case with soot from a fire. “…dust and gas trying to move with one another is unstable and causes dust grains to come together,” says [Phil] Hopkins [Professor of theoretical astrophysics at Caltech]...These gas-dust instabilities are at play anywhere in the universe that a force pushes dust through gas, whether the forces are stellar winds, gravity, magnetism, or an electrical field.” The team’s simulations show material swirling together, with clumps of dust growing bigger and bigger.” (2)
Computer simulations looking at how dust moves through magnetized gas seems to show this clumping effect as a general mechanism. The dust grains are like boulders in a fast moving and turbulent river (the gas within a moving stream of magnetized material). As the flows wrap around these grains and pull them back and forth, the grains have a tendency to coalesce, forming ever larger clumps. This is not just applicable to planet formation in proto-planetary disks, but may also extend to interstellar space:
“As examples, we introduce several new instabilities, which could see application across a variety of physical systems from atmospheres to protoplanetary disks, the interstellar medium, and galactic outflows.” (3) Read More…
The announcement of the discovery a new object in the outer solar system may bring us a step closer to the elusive Planet X (more recently dubbed Planet Nine). This new dwarf object, known as 2015 TG387, is a distant member of the mysterious scattered disk of objects beyond the Kuiper Belt. This particular object can travel so far away from the Sun during its orbit that it moves through the inner Oort cloud of comets, beyond 2000AU:
“The newly discovered object is called 2015 TG387, is probably a small dwarf planet at just 300km across, and is incredibly far away. It is currently lying about two and a half times further away from the Sun than Pluto is. It often reaches much further away. Its orbit takes it to about 2,300 AU — that is 2,300 times as far away from the sun as we are, and vastly more than the already huge 34 AU that the distant Pluto sits at.” (1)
The object’s vast orbit is so vast that it takes about 40,000 years to do one circuit around the Sun. Yet, its orbit is highly eccentric. It distance from the Sun varies from 64AU at perihelion to 2037AU at aphelion. Incredibly, then, it skirts both the Kuiper Belt and the inner Oort cloud, transiting between these quite distinct belts of objects.
As more objects are discovered between the Kuiper Belt and the inner Oort cloud (a torus-shaped disk of comets), the classifications of these objects are becoming more complex. A significant factor is whether these objects have perihelia within 40AU, which might briefly bring them within the influential scope of the planet Neptune. Extreme scattered disk objects fall into this category. Significantly, 2015 TG387 is fully detached from this influence at perihelion, and may be considered to be an inner Oort cloud object. Read More…
The Earth’s surface is subject to great change over geological time periods, due to the movement of tectonic plates, and volcanic activity, as well as long-term weathering and erosion. As a result, craters caused by meteorite, asteroid and comet bombardment long ago is gradually eradicated. We therefore look to the Moon’s cratered surface to provide clearer evidence of the bombardment history of the Earth/Moon binary. That cratering history is then compared to other planets and objects in the inner solar system, allowing astronomers to discern patterns in cratering over long time periods. One of the most significant events is the late, heavy bombardment. Following a period of relative quiet after the formation of the planets, this mass bombardment was thought to have occurred about 3.9 billion years ago:
“Competing models of meteorite-impact rate for the first 2 billion years (Ga) of Earth and Moon history. Note that Earth is believed to have formed about 4.55 Ga before present. Two hypotheses are shown: exponential decay of impact rate (dashes); and cool early Earth–late heavy bombardment (solid curve).” [see right-hand graph] (1).
More recently however, there has been a gradual realisation that this was not a sudden, dramatic event, but rather a sustained period of impacts by what were some colossal bodies:
“Recent high-resolution orbital data and images, more refined techniques for studying small lunar, terrestrial, and other impact samples and a better understanding of their ages, and improved dynamical models based on orbital and sample data have caused a paradigm shift in how we think about the lunar impact rate … The long-held idea of a “lunar cataclysm” at ~3.9 Ga is being replaced by the idea of an extended lunar bombardment from ~4.2 Ga to 3.5 Ga.” (3) Read More…
Somehow or other (and it’s by no means clear how), some exoplanet gas giants whizz around their stars at great proximity. The hottest of these objects so far discovered is an exoplanet named Kelt-9b. It is a sub-brown dwarf of ~3 Jupiter masses. It’s so close to its parent star that its rotation is tidally locked, and orbits the star in just 36 hours. The temperature of its ‘dayside’ is over 4000 degrees C. This remarkably high temperature is likely due to the immense amount of stellar radiation Kelt-9b is subjected to. This temperature and stellar irradiation is driving off huge amounts of hydrogen from Kelt-9b’s atmosphere, creating an extended envelope of atomic hydrogen gas (1). Other similar tailed gas giants have been studied before (2,3). One can only imagine how spectacular this must look – a gas giant ‘comet’ streaming out a tail from near to or even within its parent star’s extended corona.
New analysis of Kelt-9b’s atmosphere has confirmed the presence of iron and titanium atoms within the planet’s atomic chemical soup (4). It’s known that brown dwarfs can have cloudy atmospheres containing liquid iron rain, as well as other atmospheric dusts (5). These dusty, cloudy atmospheres tend to form below 2,500 degrees Celsius, and then clear when the brown dwarf drops its temperature below about 1,500 degrees C. Read More…
My yelp of delight upon hearing about this on the radio this morning was joyous. Mrs DarkStar commented that few homes in the land would have met such a story in this way. True, but few householders have written 98% of a book about missing planets and novel forms of planetary formation, and just need one more jigsaw piece to finish it. And here it is: Space grease! Admittedly, this does not sound too exciting. But I have faced a problem figuring out just what can stick interstellar protoplanets together, given a lack of gas pressure in interstellar space (this gas pressure, apparent in the early solar system’s pre-solar nebula and subsequent protoplanetary disk, likely plays a part in granular accretion). What better way to accrete than space grease. There’s masses of it out there (10 billion trillion trillion tonnes in the Milky Way), created in stars, and distributed across space:
“Prof Tim Schmidt, a chemist at the University of New South Wales, Sydney and co-author of the study, said that the windscreen of a future spaceship travelling through interstellar space might be expected to get a sticky coating. “Amongst other stuff it’ll run into is interstellar dust, which is partly grease, partly soot and partly silicates like sand,” he said, adding that the grease is swept away within our own solar system by the solar wind.” (1)
Material moving through interstellar space encounters this grease routinely, then. It will stick to surfaces. Over billions of years of such interactions, major accumulations of this type of gloop will build up on objects, like interstellar comets, and free-floating asteroids and planets.
The first interstellar object to be directly observed moving through our solar system was 1I/’Oumuamua, a tumbling, shard-shaped object which was detected last autumn (2,3). Such objects were expected to behave like comets, and outgas as they approach the Sun. However, this object did not spray the solar system with its internal gases, leading astronomers to conclude that this object had originally been an asteroid which had been ejected from another star system. However, recent observations and work on 1I/’Oumuamua’s trajectory indicate that its motion is being affected by another factor beyond gravitational interactions – it is moving faster than it should (4). This is thought to be due to outgassing after all, leading to the conclusion that this object is an interstellar comet after all (5).
“Such outgassing is a behaviour typical for comets and contradicts the previous classification of `Oumuamua as an interstellar asteroid. “We think this is a tiny, weird comet,” commented Marco Micheli. “We can see in the data that its boost is getting smaller the farther away it travels from the Sun, which is typical for comets.”
““We did not see any dust, coma, or tail, which is unusual,” explained co-author Karen Meech of the University of Hawaii, USA. Meech led the discovery team’s characterisation of `Oumuamua in 2017. “We think that ‘Oumuamua may vent unusually large, coarse dust grains.”” (5)
In conjunction with a scientist from the University of Michigan, the Caltech team who originally coined the term Planet Nine in 2016 have written a new paper about its formation, and the subsequent layout of the outer solar system. Having set out the evidence for this proposed object in the paper (1), they note three possible scenarios for its formation:
1) The planet’s capture from the retinue of a passing star; or, alternatively, the capture of a free-floating interstellar planet
2) The planet’s semi-ejection from the inner solar system and subsequent gradual drift outwards
3) The planet’s formation in situ.
All three of these scenarios require certain conditions for them to work, which means that no single formation theory stands out as particularly probable. The capture and scattering models depend upon the interjection of outside bodies (passing stars or brown dwarfs, or objects in the Sun’s birth cluster). The in situ formation of a planet so far from the Sun implies that the Sun’s protoplanetary disk was significantly larger than generally accepted. The formation of Planet Nine in its calculated position thus remains problematic, based upon standard models of planetary and solar system formation (e.g. the Nice model). Further, whatever processes which placed it in its proposed current position would have significantly affected the layout of the Kuiper belt within its overarching orbit. This factor is what the current investigation described by this paper aims to solve.
This paper then describes computer simulations of the early Kuiper belt, and how the shape and extent of the fledgling belt may have affected the complex interplay between it, Planet Nine, and the objects in the extended scattered disk (1). The research team modelled two distinct scenarios for the early Kuiper belt, each of which matches one or more formation scenarios for Planet Nine. The first is a ‘narrow’ disk, similar to that observed: The Kuiper disk appears to be truncated around 50AU, with objects found beyond this zone likely having been scattered outwards by processes which remain contentious. The second scenario is a ‘broad’ disk, where objects in the Kuiper belt would have routinely populated the space between Neptune and the proposed orbit of Planet Nine, hundreds of astronomical units out. This would match a formation scenario involving an extensive protoplanetary disk. Read More…
The shard-like asteroid from deep space which shot through the solar system last years, known as ‘Oumuamua, set many an astronomer’s heart racing. The peculiar body was determined to be the first confirmed interstellar asteroid to have been observed (1). It’s possible, though, that other comets which pursue so-called hyperbolic orbits (moving fast enough to escape the solar system) also have an interstellar origin, rather than having originated from the Oort Cloud. A team of Spanish astrophysicists, who have more than a passing interest in the topic of Planet X, have performed powerful computer simulations to build up a picture of the trajectories and spatial origins of various hyperbolic comets (2). The objects they chose to consider have inbound velocities greater than 1km/s
Following adjustment for the Sun’s own movement through space towards the Solar Apex, interstellar visitors would likely have a more or less random distribution to their radiants (the position in the sky from which they came, rather like meteor showers striking the Earth’s atmosphere). The Spanish team carried out statistical analysis on the emerging sky maps of these radiants, and looked for patterns or clusters of these origin points. Statistically significant patterns did indeed emerge from the data. A particularly large source was located in the zodiacal constellation Gemini. Such a clustering might indicate a number of possibilities, which the astrophysicists explore in their paper.
One possibility is a close flyby of a star in the past which could have disrupted the outer edges of the distant Oort Cloud, sending comets in-bound towards the Sun. Looking at the tracking of candidate flybys in the (by Cosmic standards) relatively recent past, Carlos de la Fuente Marcos, Raul de la Fuente Marcos & S. J. Aarseth argue that there is a possible correlation between this cluster of hyperbolic orbit radiants in Gemini, and a close flyby of a neighbouring binary red dwarf system known as Scholz’s star some 70,000 years ago (2). At a current distance of about 20 light years, Scholz’s star may be a close neighbour to the Sun relatively speaking, but even so it took a while for it to be discovered. This was probably because of a combination of factors: Its proximity to the Galactic plane, its relative dimness, and its slow relative movement across the sky (3). Its distance was less than a light year 70,000 years ago, and its rapid movement away from us in the intervening time helps to explain why it was difficult to detect as a neighbouring binary star: Its retreating motion is mostly along our line of sight, making it difficult to differentiate from background stars. Read More…