NASA's New Horizons Discovered a Large Surprise in the Kuiper Belt | Hacker News Reader

NASA's New Horizons Discovered a Large Surprise in the Kuiper Belt

sciencealert.com

57 pointsBrajeshwar26 comments

This is the surprise:

> Data from the New Horizons probe as it sails serenely through the Kuiper Belt hints at unexpected levels of particles where dust ought to be thinning out, suggesting the donut-shaped field extends significantly farther from the Sun than previous estimates suggest.

Does that dust explain some gravitational anomalies?

im no astrophysicist, but if you mean the anomolies that lead us to believe that there may be a planet 9, I dont think so. This dust would be assumed to be spread around evenly, and the anomalies that make us think there is another planet would have to be clustered together in an orbit.

I'm surprised to see a clickbait headline like this on HN. Thanks for posting that info.

"It's the most recent in a growing body of evidence that our understanding of the outer Solar System is lacking..."

Isn't this -- finding out that what we didn't know is far greater than we realized -- typical in any field of science or even profession? When I was 5 years into my programming career I had the cocky feeling of knowing everything. 20 years later I feel more like I know nothing because every day I'm discovering more about my profession that I never even knew existed (thank you, HN!).

We tend towards finding smaller and smaller details that we didn't understand as a field matures unless it gets upended by large new discoveries. Classical mechanics for example, we can safely say we've got that pretty much locked down and know what it's good for and where we need to apply other methodologies. Also we have to zoom out from the individual view when thinking about collective knowledge in an entire field. Each individual person has a vast amount they can continue to learn of course but fields as a whole can tend towards more complete knowledge of a particular topic.

> Classical mechanics for example, we can safely say we've got that pretty much locked down and know what it's good for and where we need to apply other methodologies

Yet even classical mechanics holds some surprising mysteries, such as how bicycles self-stabilize [1].

[1] https://www.aip.org/history-programs/niels-bohr-library/ex-l...

I'm not sure how closely that applies. We didn't, but mostly because people hadn't really studied it and hadn't worked through the mechanics. As soon as we really started looking AFAIK the solution came pretty quickly; it's a combination of 3 things that all make the bike steer towards where it leans: gyroscopic precession, head angle and CoM of the front steering section. All 3 of those things can be tuned to be larger or smaller and that affects the velocity required to achieve stability.

https://www.youtube.com/watch?v=oZAc5t2lkvo

Note that near the end of that video he says:

> But amazingly, even for a riderless bike science currently doesn't what it IS about the special combinations of variables that enables a bike to stay up on its own. We just know that some combinations work and others don't.

There have been studies characterizing it more since then both analytically and quantatatively. There have been model bikes built with counter rotating weights to eliminate the gyroscopic effect and it still works. Part of the complexity is they all work together so the parameter space is complex. People have isolated the effect of things like the head angle though or the gyroscopic effect.

I'd bet that's written by a journalist, not a scientist.

And yet, it is also claimed that:

> Astronomers using the Webb telescope discovered complex organic molecules in a galaxy located over 12 billion light-years away.

https://edition.cnn.com/2023/06/06/world/webb-telescope-dist...

To me, this sort of claim is beyond embarrassing. How can we possibly reconcile knowing about organic molecules, and not know about our backyard.

It's contradictory feeling but it's often easier to know more about small things far away than small things nearby.

The reason? Light.

Webb was able to detect the absorption characteristics of PAH (the organic molecules in question) from a distance because there was light from behind illuminating it (and it was absorbing only parts of that light). We know roughly what the light being emitted "looks like" so we are able to extrapolate based on what light isn't present what is in that region. And it wasn't as if individual particles were being seen but rather there is a sufficient density of these molecules spread out in the regions where they were detected that when the light passed through them, it was noticeable from a distance. Kinda like how you can't see the air but you can see the sky.

I'm probably not explaining it super well but it's the phenomenon where you can see the gaps in between up close but from far away it looks like one big blob.

But point being Webb was able to make that discovery because those molecules basically had a giant lamp shining on them from behind and we the observer are at such a distance that we can see all the little bits of information that would otherwise be indistinguishable from noise all together at once.

Now comparatively, the stuff out in the far reaches of our solar system have a lamp shining on them (our sun) but we are on the wrong side to be able to see the shadows that are cast. So unfortunately that means if we want to learn about this blindspot of ours we have to physically go out there to see it.

There are places where science doesn't understand things, but we understand (or think we understand) well enough to place limits on what is happening. Then there are places that we know out current theories are not enough to explain things, but we don't have a clue what a theory that explains them are. Once in a while we think something is the first but when we get more detail we discover current theories are not enough and so we expand the number of things we need to figure out.

In general I would expect this to be a case where we didn't expect something but once we look closer we discover it fits with our current known physics - this is the majority of "interesting" discoveries. However once in a while we discover something unknown.

I'm still cheerleading for discovery of a Mars to Earth mass planet out there, with an exospheric temperature low enough it could retain helium. If it existed it could be the best place in the solar system to mine the fusion fuel helium-3.

Gas giants hold onto their gases, not because they're cold, but because they're massive. I doubt you could get a planet to form with liquid or solid helium on the surface. Building a planet generates a great deal of heat and pressure.

And we'd know if there was another gas giant in the kuiper belt. I couldn't find estimates on how much mass is in the oort cloud, but probably not enough to form a orbit with enough mass to make a gas giant.

Edit: Just found the wikipedia section on the mass of the oort cloud. Roughly estimated at 5 earth masses. Neptune, which isn't quite massive enough to be a gaseous planet, is 17 earth masses. Saturn, our smaller gas giant is 95 earth masses

All planets and moons hang on to their gasses through gravity. I would think our understanding of solar system formations and solar winds makes the likelihood of lots of helium being in the outer system being quite high.

The temperature is not related to holding on to the helium, but to its density for higher efficiency farming.

The temperature at the exobase does have an effect on retention of helium. If it's high enough (relative to the escape energy of the planet) the high energy tail of the thermal distribution will leak atoms into space.

I thought you can just shovel He-3 from the ground on the Moon?

At about 10ppb concentration in the regolith. Without really serious heat recycling the energy cost of extracting it would be higher than the fusion energy it would yield.

Could you skim it off a gas giant? If part of a gravity assist there would be no gravity well penalty.

That would be (from Uranus) the next best idea (or perhaps scooping suborbitally lobbed 3He tanks in a rugged cone-shaped collector), but I think launching it to space in the normal way from a hypothetical smaller planet would be better, if such a planet existed.

Here is an official NASA article on the discovery: https://www.nasa.gov/missions/new-horizons/nasas-new-horizon...

It probably has a better title too, considering the more clickbaity title above.

There is a paper linked on the article which says potential causes for the dust distribution are Kuiper belt object collisions and radiation pressure (I'm assuming from the sun?) pushing dust outward

> New data (Figure 3) at larger heliocentric distances show that the SDC-reported dust f l uxes, out to 55 au, remained higher than current models expected. Each of the three physical phenomena: optical properties and radiation pressure (Arnold et al. 2019); compositional variation between silicates and ice (Grigorieva et al. 2007); and a further reaching than currently identif i ed distribution of dust-producing bodies in the solar system (Fraser et al. 2023), may contribute to the data/model deviation.

I hope it lasts also. I am wondering if these particles will continue on to the ort cloud ?

https://en.wikipedia.org/wiki/Oort_cloud

Propably a remnant of the birthplace of our sun? Basically a slice of the nebula that spawned the system dragged along for the longest ride ever?

Reply on news.ycombinator.com