[HN Gopher] A Spiral Structure in the Inner Oort Cloud
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A Spiral Structure in the Inner Oort Cloud
Author : gnabgib
Score : 128 points
Date : 2025-06-04 23:22 UTC (23 hours ago)
(HTM) web link (iopscience.iop.org)
(TXT) w3m dump (iopscience.iop.org)
| girvo wrote:
| Meta: I can't even get into the site, the hCaptcha shows an image
| (a table and chairs) that never shows up even after 20+ "Skip"
| clicks...
| SCUSKU wrote:
| Here's the PDF:
| https://iopscience.iop.org/article/10.3847/1538-4357/adbf9b/...
| tonyhart7 wrote:
| I fucking hate that chaptcha
| recursive wrote:
| I got the same thing. The correct answer for me was the fancy
| desserts, because they go on a fancy restaurant table I guess.
| samyok wrote:
| you have to click on the fruit cups, as it asks what fits the
| "theme" of the image.
|
| here's the pdf, though:
| https://iopscience.iop.org/article/10.3847/1538-4357/adbf9b/...
| w10-1 wrote:
| Also no access, even after passing human validation - screen
| dark.
| dcassett wrote:
| I've been using the links browser for HN and fall back to a
| full-fledged browser if I get blocked. Links (and Lynx) give me
| no problems with TFA.
| graemep wrote:
| > I can't even get into the site, the hCaptcha shows an image
| (a table and chairs) that never shows up even after 20+ "Skip"
| clicks...
|
| But someone's metrics are showing 20+ bot request blocked!
| misja111 wrote:
| The bot doesn't believe you're human
| gs17 wrote:
| It's a really poor design. "Fits the theme", not "is this
| object". I had a lighthouse and it wanted me to click sharks,
| because they're both "water" themed.
|
| I asked Gemini to solve this "puzzle" and it could do it.
| Whatever weird filter they're trying to apply to the images
| doesn't work well enough.
| coke12 wrote:
| Our own solar system has what appear to be spiral arms. Very cool
| finding.
| dotancohen wrote:
| Yes, this is interesting, finding complex structures that are
| found at multiple scales is rather amazing.
|
| The paper attributes the solar system's spiral structure to the
| galactic tide. If I'm not mistaken, and this might be outdated,
| the galactic spiral structure is attributed to massive clumping
| - massive particles attract.
|
| ("Massive" meaning particles with mass - not necessarily large.
| "Particles" meaning macroscopic particles, not subatomic.)
| dachris wrote:
| It's amazing, yes, and at the same time, it makes perfect
| sense.
|
| (Somewhat) similar mechanisms are at work whether you're
| pulling together stars into a galaxy, hydrogen gas into a
| solar system or water towards the drain of your bath tub - a
| pull towards the center, the centripetal force, slight
| variations producing "artifacts".
| dotancohen wrote:
| Well, I would not call these two mechanisms similar, though
| the artifacts may be similar. I wonder if in fact the
| spirals are similar, for that matter if mathematicians even
| have terminology for different types of spirals.
|
| The spirals shown in the paper do look like idealised
| spirals of very young galaxies, shortly after the bar
| phase. I wonder, other than spirals, what other artifacts
| such processes might cause.
|
| Imagine an accretian disk undergoing fusion in spiral-
| shaped filaments!
| ninkendo wrote:
| Also, galaxy spirals are very much an open question.
| Galaxies don't rotate the way you'd expect from the
| matter you see, and it's the main reason we hypothesize
| the existence of dark matter. Unless dark matter is the
| reason the Oort Cloud develops spiral arms, I'd wager the
| mechanisms are quite different.
| awongh wrote:
| > Galaxies don't rotate the way you'd expect from the
| matter you see
|
| In what way?
| gosub100 wrote:
| Given the stars' angular velocity, they should fly out
| away from the galactic center, but they stay confined to
| their disc.
| AStonesThrow wrote:
| It will be really exciting if we confirm one, then.
|
| The spiral structure here is a hypothesis within a
| hypothesis. Whatever objects comprise the Oort Cloud, they
| haven't been directly observed. Scientists have inferred its
| existence from a variety of comets that seem related and have
| very, very long orbital periods, such as 200 years, or 2,000
| years. So these comets are observed once-in-a-lifetime, or
| once-in-a-civilization, and the hypotheses say that they're
| being dislodged somehow from a "cloud of planetesimals" where
| a bunch more of them are found.
|
| But this supposed cloud would be extremely sparse: plenty of
| space in-between the very small icy bodies, and individually,
| they're so much smaller, and so distant from the Sun, that
| they don't reflect enough light to our telescopes. They
| really don't send signals in other wavelengths, either, like
| a pulsar or quasar or something with an active powerplant.
|
| This is beyond the Kuiper Belt, even; the Kuiper Belt, if it
| indeed be a belt, has offered us a couple of directly-
| observed objects, including Pluto and Charon.
|
| So it's nice to conjecture and invent proposals for some kind
| of structure there, but the very existence and extent of the
| Oort Cloud is something that's been extrapolated and inferred
| from secondary evidence.
| metalman wrote:
| confirmation is unlikely, as imaging and detection out
| there is not a thing from the intro, "Here we discuss
| dynamics underlying the Oort spiral and (feeble) prospects
| for its observational detection." we need a whole new class
| of space based telescopes for this, and other things like
| direct observation of surface conditions on.exo planets
| jajko wrote:
| Do we know why ie Saturn rings are not spiral-like? Ie due to
| their age (some relatively recently broken down comets) or
| some other forces that keep them spread evenly? Or just
| gravity is too weak amongst them for those smaller pieces of
| rock
| seanhunter wrote:
| Just trying to understand what you're getting at here.
| About what axis would you expect them to spiral? From
| normal mechanics + gravity I would expect them to orbit
| more or less elliptically about the polar axis of Saturn
| rather than spiral, but I don't know much about
| astrophysics.
| antognini wrote:
| Moons close to the rings tend to keep the particles of the
| ring confined within a narrow band (which is why they are
| called "shepherd moons").
| throwawaymaths wrote:
| IIRC the galactic spiral is believed explicitly to be _not_
| due to gravitational attraction so much as shock wave
| /traffic jam dynamics (transmitted through gravitational
| force ofc) -- not sure if that's what you meant by clumping.
| antognini wrote:
| The basic theory of spirals is basically that you get spiral
| structure when the orientation of elliptical orbits shifts
| with semi-major axis. This leads to what appear to be spiral
| arms that have higher densities. In these high density
| regions you get collisions of gas clouds which leads to star
| formation. The star forming regions produce lots of bright,
| blue stars, which then make the spiral arms very visible in
| optical wavelengths.
|
| In this case of the Oort cloud the galactic tides would be
| what are responsible for inducing the change in orientation
| of the elliptical orbits as a function of semi-major axis.
| doctoboggan wrote:
| > The spiral structure was first identified by examining the
| simulation in the Hayden Planetarium in preparation for a new
| space show that describes and visualizes the Oort cloud.
|
| That's a pretty cool way to discover something like this. Here is
| the simulation animation:
|
| https://drive.google.com/file/d/1TuacHdAeZ5J8wNAJvlYv435x9Oj...
| tristramb wrote:
| You might also appreciate W. W. Morgan's account of his
| discovery of the Perseus Spiral Arm of our Galaxy in his
| observational data on OB stars:
|
| "This was in the fall of 1951, and I was walking between the
| observatory and home, which is only 100 yards away. I was
| looking up in the sky ... just looking up in the region of the
| Double Cluster [in Perseus], and I realized I had been getting
| distance moduli corrected the best way I could with the colors
| that were available, for numbers of stars in the general region
| ... Anyway, I was walking. I was looking up at the sky, and it
| suddenly occurred to me that the double cluster in Perseus, and
| then a number of stars in Cassiopeia, these are not the bright
| stars but the distant stars, and even Cepheus, that along there
| I was getting distance moduli, of between 11 and 12, corrected
| distance moduli. Well, 11.5 is two kiloparsecs ... and so, I
| couldn't wait to get over here and really plot them up. It
| looked like they were at the same distance ... It looked like a
| concentration ... And so, as soon as I began plotting this out,
| the first thing that showed up was that there was a
| concentration, a long narrow concentration of young stars ...
| There are HII regions along there too ... And that was the
| thing that broke [the problem] down."
|
| Full article here: https://articles.adsabs.harvard.edu/cgi-
| bin/nph-iarticle_que...
| YesThatTom2 wrote:
| The ads for Hayden Planetarium show mostly highlight that it's
| narrated by Pedro Pascal.
|
| But, yeah, the spiral thing is cool too.
| dedicate wrote:
| I always pictured it as, like, a super scattered snowball fight
| way out in the boonies. How does something so delicate even hold
| that shape out there?
|
| This completely change how we should think about the 'edge' of
| our solar system!
| HappMacDonald wrote:
| Kamina most likely approves
| eli_gottlieb wrote:
| I understood that reference.
| Eduard wrote:
| could someone explain the significance of this finding? Is it
| remarkable for being a definable structure in a previously
| thought random distribution of bodies that make up the Oort
| cloud?
| machenesonk wrote:
| could universe have a spin?
| twic wrote:
| They could really do with a 3D model of this, it's rather hard to
| visualise from the views from two different directions.
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