> 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:
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."
The ads for Hayden Planetarium show mostly highlight that it’s narrated by Pedro Pascal.
But, yeah, the spiral thing is cool too.
Eduard · 1h ago
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?
coke12 · 11h ago
Our own solar system has what appear to be spiral arms. Very cool finding.
dotancohen · 9h ago
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 If I'm not mistaken, and this might be outdated, the galactic spiral structure is attributed to massive clumping - massive particles attract.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 · 8h ago
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 · 7h ago
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 · 47m ago
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.
AStonesThrow · 7h ago
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 · 4h ago
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 · 3h ago
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
dedicate · 8h ago
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!
girvo · 12h ago
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...
graemep · 3h ago
> 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!
That's a pretty cool way to discover something like this. Here is the simulation animation:
https://drive.google.com/file/d/1TuacHdAeZ5J8wNAJvlYv435x9Oj...
"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...
But, yeah, the spiral thing is cool too.
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.)
(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".
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!
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.
This completely change how we should think about the 'edge' of our solar system!
But someone's metrics are showing 20+ bot request blocked!
here's the pdf, though: https://iopscience.iop.org/article/10.3847/1538-4357/adbf9b/...