Looking for new Kuiper Belt targets for the New Horizons spacecraft pays off in multiple ways. While we can hope to find another Arrokoth for a flyby, the search also contributes to our understanding of the dynamics of the Kuiper Belt and the distribution of comets in the inner Oort Cloud. Looking at an object from Earth or near-Earth orbit is one thing, but when we can collect data on that same object with a spacecraft moving far from the Sun, we extend the range of discovery. And that includes learning new things about KBOs that are already cataloged, as a new paper on observations with the Subaru Telescope makes clear.
The paper, in the hands of lead author Fumi Yoshida (Chiba Institute of Technology) and colleagues, points to Quaoar and the use of New Horizons data in spawning further research. A key aspect of this work is the phase angle as the relative position of the object changes with different observing methods.
One of the unique perspectives of observing KBOs from a spacecraft flying through the Kuiper Belt is that they can be observed with a significantly larger solar phase angle, and from a much closer distance, compared with ground-based or Earth-based observation. For example, the New Horizons spacecraft observed the large classical KBO (50000) Quaoar at solar phase angles of 51°, 66°, 84°, and 94° (Verbiscer et al. 2022). Ground-based observation can only provide data at small solar phase angles (≲2°). The combination of observations at large and small solar phase angles provides us with knowledge of the surface reflectance of the object and enables us to infer information about a KBO’s surface properties in detail (e.g., Porter et al. 2016; Verbiscer et al. 2018, 2019, 2022).
In the new paper, the Subaru Telescope’s Hyper Suprime-Cam (HSC) is the source of data that is sharpening our view of the Kuiper Belt through wide and deep imaging observations Located at the telescope’s prime focus, HSC involves over 100 CCDs covering a 1.5 degree field of view. Early results from Yoshida’s work support the idea that we can think in terms of extending the Kuiper Belt, whose outer edge seems to end abruptly at around 50 AU. This adds weight to recent work with the New Horizons team’s Student Dust Counter (SDC), which has been measuring dust beyond Neptune and Pluto. The SDC results point to such an extension. See the citation below, and you might also want to check New Horizons: Mapping at System’s Edge in these pages.
Other planetary systems also raise the question of why our outer debris belt should be as limited as it has been thought to be. Says Yoshida:
“Looking outside of the Solar System, a typical planetary disk extends about 100 au from the host star (100 times the distance between the Earth and the Sun), and the Kuiper Belt, which is estimated to extend about 50 au, is very compact. Based on this comparison, we think that the primordial solar nebula, from which the Solar System was born, may have extended further out than the present-day Kuiper Belt.”
If it does turn out that our system’s early planetary disk was relatively small, this could be the result of outer objects like the much discussed (and still unknown) Planet 9. The distribution of objects in this region thus points to the evolution of the Solar System, with the implication that further discoveries will flesh out our view of the process.
The Subaru work was focused on two fields along New Horizon’s trajectory, an area of sky equivalent to about 18 full moons. Using these datasets, drawn from thirty half-nights of observations, the New Horizons science team has been able to find more than 240 objects. The new paper pushes these findings further by studying the same observations with different analytical tools, using JAXA software called the Moving Object Detection System, which normally is deployed for spotting near-Earth objects. Out of 84 KBO candidates, seven new objects have emerged whose orbits can be traced. Two of these have been assigned provisional designations by the Minor Planet Center of the International Astronomical Union.
Image: Schematic diagram showing the orbits of the two discovered objects (red: 2020 KJ60, purple: 2020 KK60). The plus symbol represents the Sun, and the green lines represent the orbits of Jupiter, Saturn, Uranus, and Neptune, from the inside out. The numbers on the vertical and horizontal axes represent the distance from the Sun in astronomical units (au, one au corresponds to the distance between the Sun and the Earth). The black dots represent classical Kuiper Belt objects, which are thought to be a group of icy planetesimals that formed in situ in the early Solar System and are distributed near the ecliptic plane. The gray dots represent outer Solar System objects with a semi-major axis greater than 30 au. These include objects scattered by Neptune, so they extend far out, and many have orbits inclined with respect to the ecliptic plane. The circles and dots in the figure represent their positions on June 1, 2024. Credit: JAXA.
The semi-major axes of the two provisionally designated objects are greater than 50 AU, pointing to the possibility that as such observations continue, we will be able to extend the edge of the Kuiper Belt. Further work using the HSC is ongoing.
Image: An example of detection by JAXA’s Moving Object Detection System. Moving objects are detected from 32 images of the same field taken at regular time intervals (the images in the orange frames in the above figure). Assuming the velocity range of Kuiper Belt objects, each image is shifted slightly in any direction and then stacked. The green, light blue, and black framed images are the result of stacking 2 images each, 8 images each, and 32 images, respectively. If there is a light source in the center of a single image as well as each of the overlapping images, it is considered a real object. (Credit: JAXA)
Observations of tiny objects at these distances are fraught with challenges at any time, but the authors take note of the fact that while their datasets cover the period between May 2020 and June 2021 (the most recently released datasets), their particular focus is on the June 2020 and June 2021 data. This marks the time when the observation field was close to opposition; i.e., directly opposite the Sun as seen from Earth. At opposition the objects should be brightest and their motion across the sky most accurately measured.
Additional datasets are in the pipeline and will be analyzed when they are publicly released. The authors intend to adjust their software in a computationally intensive way that will bring more accurate results near field stars that can otherwise confuse a detection. They also plan to deploy a machine-learning framework as the effort continues. Meanwhile, New Horizons presses on, raising the question of its successor. Right now we have exactly one spacecraft in the Kuiper Belt. How and when will we build the probe that continues its work?
The paper is Yoshida et al., “A deep analysis for New Horizons’ KBO search images,” Publications of the Astronomical Society of Japan (May 29, 2024). Full text. The SDC paper is Doner et al., “New Horizons Venetia Burney Student Dust Counter Observes Higher than Expected Fluxes Approaching 60 au,” The Astrophysical Journal Letters Vol. 961, No. 2 (24 January 2024), L38 (abstract).
Is there any possibility that the outer 50AU “limit” to the Kuiper belt is due to an outer planet like Neptune that swept the volume at that edge before migrating inwards to its present orbit?
Alternatively, could a rogue/wandering planet have swept up or deflected the KBOs before eventually heading away from our system?
Or do both ideas fail to demonstrate the distribution of KBOs beyond 50 AU as our observations currently indicate?
Yes. That is the whole idea of the Kuiper belt, where Neptune’s gravity deflects it’s small, icy bodies towards Jupiter which deflects them further out into the Oort cloud. NASA https://science.nasa.gov/solar-system/kuiper-belt/facts/
The Kuiper Belt is not a stable system, in fact it is very similar to our oceans. Typhoons, storms and rough seas take place over 100,000s to million of years. The passage of nearby stars and our solar system going through the galaxies arms cause incredibly large amounts of debris to be captured by the Kuiper Belt.
Something I just noticed today is the large Kuiper Belt objects also have large moons orbiting them. This is not an ancient system of objects but is continually being resupplied by new material. When these storms come through we may see in our own earths history the extinction events caused by large Kuiper Belt objects being thrown into our inner solar system…
At 1000 AU a 1 solar mass star passed the solar system 2.47 million years. Homo habilis (lit. ‘handy man’) the first appeared
In the latest Gaia third data release one can find extremely small proper motion components for the star HD 7977. This, together with the radial velocity measurement lead to the conclusion that this star passed very close to the Sun in the recent past. Such a very close approach of a one solar mass star must result in noticeable changes in the motion of all Solar System bodies, especially those on less tight orbits, namely long-period comets (LPCs) and Kuiper belt objects. We estimate and present these effects. Our current knowledge on the stellar surroundings of the Sun found in the latest Gaia catalogues allowed us to perform numerical integrations and prepare a list of potential stellar perturbers of LPCs. We use this list, made available in the StePPeD database. To study the past motion of LPCs under the simultaneous action of the Galactic potential and passing stars, we use precise original cometary orbits taken from the current CODE catalogue. We examine the reliability of the extremely small proper motion of HD 7977 concluding that this star can be an unresolved binary but according to the astrometry covering more than a century, the current Gaia results cannot be ruled out. We present the parameters of a very close passage of this star near the Sun. We also show examples of the strong influence of this passage on the past motion of some LPCs. We also discuss the possible influence of this perturber on other Solar System bodies. It is possible that 2.47 Myr ago the one solar mass star HD 7977 passed as close as one thousand au from the Sun. Such an event constitutes a kind of dynamical horizon for all studies of the past Solar System bodies’ dynamics.
https://arxiv.org/abs/2312.11124
In teh conclusions section the closest approach of 0.012 pc (~=2000 au) was just p=0.1, so I am not sure where they got the 1000 au from in teh abstract. [I may well have missed in the text.] Even the larger distance of 0.06 pc (~- 23000 AU) with a p = 0.9 is well inside the Oort cloud (and presumably the basis for their comet pertubing analyses).
What I think would make an interesting post is whether such a close approach could explain some features of our system – e.g. the KP boundary, the anomalous compositions of moons in the outer planets, the age of Saturn’s rings, etc. I don’t want to get into Veliskovsky territory, but I do wonder whether a close encounter at some distance might explain more than 1 or 2 anomalies that we think we have found in our system.
I think it is heading straight away from us so some question as to how close it may have come. I did find a match for a major impact 2.5 million years ago called the Eltanin impact. Looks like it was a very large impactor and if comet may have caused a large Tsunami since a large percentage of it would have disappeared when it hit the ocean. The geologist look at the pacific from the view of the ring of fire and major earthquakes but they do not see it is the largest basin for giant impacts…
https://en.wikipedia.org/wiki/Eltanin_impact
Most of these objects will have a lot water and so a source of fusion for future colonists.
I wonder if Gliese 710 might come inward enough to perturb them
Scholz’s star back 70,000 years ago passed within 0.25 parsec or about 80K AUs reach of us. And beside being a faint red M8 or more it can be considered a binary with a brown dwarf. In this context it might make it more of a wrecking ball than otherwise.
https://www.centauri-dreams.org/2018/03/22/a-prehistoric-close-pass/
So one can surmise that there was a perturbing event that peaked about 70,000 years ago in terms of stellar proximity – and then had consequences since – for both the Oort Cloud and the Kuiper Belt.
With the Oort Cloud, the outer of the two regions, the outside limit claims are between 20,000 and 50,000 AU. We might note that it is difficult to define the limits of a diffuse body which we can’t see. And also, we could claim that were it not for such intrusions like Scholz’s Star and brown dwarf, in its invisible majesty it might have been larger…
From discussion above, it sounds as though the Kuiper Belt would be an approximate bound for the regions swept up in the sun’s early circumstellar disk – and that the Oort Cloud is an older region that did not condense ….
Or that all these demarcations are obscured by subsequent close interactions with passing stars. Sorting all this out with Voyager is like exploring with a needle a haystack.
In addition, if the Oort Cloud and Kuiper Belt are typical divisions resulting from stellar ignition and proto-planetary disks, then there ought to be similar features wherever you find exoplanets sold. So, it would be nice to be able to detect other such features in the neighborhood. Though as dispersed and as low-lighted as our Oort Cloud and Kuiper Belt are, the best chances would likely be early phase star systems.
Just as a trial shot, since Tau Ceti has both planets and dust, thought it might be a candidate for comparison. Unfortunately G8 Tau Ceti age estimates encountered were from 5 to 10 billion years. Either Tau Ceti continues to blow a lot of smoke and dust or it started with considerably more than our system did. Nonetheless, it does suggest that Oort Clouds might survive around a number of other local stars – and that when there are close passages, the objects within them could be randomly exchanged. A Drake equation consideration when examining occurrence or likelihood of life.
Kuiper Belt objects appear to get at least as big as Pluto, but I am not sure what we are supposed to expect for object size distributions for the Oort Cloud. Clearly (?) there should be a lot of snowflakes out there, perhaps like particles associated with orbital rings – but far less tightly collected. Brown dwarfs appear to wander loose in this region of the galaxy. I suspect that if there were one in the Oort Cloud its IR signature would have been detected by now. But until only recent decades did we have abilities to detect such objects and have not. Gaia data sets might already have the answer: Whether Pluto size Oort Cloud objects are out there or not, we should likely know soon.
Gas clouds – inhomogeneities in the contents of space evolve to galaxies and such, guided by gravity and other assorted forces, which also shape interstellar and intergalactic space and its contents.
The many features of spacetime and its contents are given names to have a handle on these features in conceptualization, to better appreciate the disruptions of the original continuum.
arXiv:2407.21142 (astro-ph)
[Submitted on 30 Jul 2024]
Candidate Distant Trans-Neptunian Objects Detected by the New Horizons Subaru TNO Survey
Wesley C. Fraser, Simon B. Porter, Lowell Peltier, JJ Kavelaars, Anne J. Verbiscer, Marc W. Buie, S. Alan Stern, John R. Spencer, Susan D. Benecchi, Tsuyoshi Terai, Takashi Ito, Fumi Yoshida, David W. Gerdes, Kevin J. Napier, Hsing Wen Lin, Stephen D. J. Gwyn, Hayden Smotherman, Sebastien Fabbro, Kelsi N. Singer, Amanda M. Alexander, Ko Arimatsu, Maria E. Banks, Veronica J. Bray, Mohamed Ramy El-Maarry, Chelsea L. Ferrell, Tetsuharu Fuse, Florian Glass, Timothy R. Holt, Peng Hong, Ryo Ishimaru, Perianne E. Johnson, Tod R. Lauer, Rodrigo Leiva, Patryk S. Lykawka, Raphael Marschall, Jorge I. Núñez, Marc Postman, Eric Quirico, Alyssa R. Rhoden, Anna M. Simpson, Paul Schenk, Michael F. Skrutskie, Andrew J. Steffl, Henry Throop
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We report the detection of 239 trans-Neptunian Objects discovered through the on-going New Horizons survey for distant minor bodies being performed with the Hyper Suprime-Cam mosaic imager on the Subaru Telescope.
These objects were discovered in images acquired with either the r2 or the recently commissioned EB-gri filter using shift and stack routines.
Due to the extremely high stellar density of the search region down stream of the spacecraft, new machine learning techniques had to be developed to manage the extremely high false positive rate of bogus candidates produced from the shift and stack routines.
We report discoveries as faint as r2∼26.5. We highlight an overabundance of objects found at heliocentric distances R≳70~au compared to expectations from modelling of the known outer Solar System.
If confirmed, these objects betray the presence of a heretofore unrecognized abundance of distant objects that can help explain a number of other observations that otherwise remain at odds with the known Kuiper Belt, including detections of serendipitous stellar occultations, and recent results from the Student Dust Counter on-board the New Horizons spacecraft.
Comments: Accepted for publication in the Planetary Science Journal, 28 pages, 7 figures, 3 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2407.21142 [astro-ph.EP]
(or arXiv:2407.21142v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2407.21142
Focus to learn more
https://arxiv.org/abs/2407.21142?fbclid=IwY2xjawEZKYlleHRuA2FlbQIxMQABHbS1rmM6mPNBNJ_ecOqyjsqHfZmqaShxHfBYOqNIEfbUcf1IjBJL5z9qNA_aem_a5Rc1KVi0izLsev6-2bUGw