Hacker News Reader

Hacker News

Comment by ddahlen | Hacker News Reader

Full thread

ddahlen

If anyone is interested, here is its orbit, my old day job was to compute orbits for asteroids and comets.

(This uses wasm, meant for a desktop, and will download the asteroid catalog of about 65mb, you have been warned)

https://dahlend.github.io/ketev/#t=2009-07-01.717&sel=2026%2...

This is a big boy.

View on HN

If you turn on the 'Stars' in that, you'll see that its currently in the interesting direction of the sky - 'twards the center of the Milky Way where we've got other telescopes looking. I wonder if we would have detected it if it was 180° further in its orbit.

> Another factor that kept ED138 hidden is that it is on the same plane as our galaxy. “For the last 20 years, the object has kind of been looping its way across the Milky Way, from our point of view,” Holman explained. “People don’t typically search for things in the Milky Way, because there’s so many stars that it’s really hard to find moving objects.” [1]

This thing was actually found despite its location, not because of it. If it had been in the opposite part of the sky we almost certainly would have spotted it sooner, given that it's one of the brightest TNOs we've discovered.

We're finding it now because Vera Rubin (the instrument that found it) just came online and is exceptionally good at finding these kinds of objects specifically, even when they're hiding amidst a dense population of stationary background stars.

[1] https://edition.cnn.com/2026/10/28/science/ed138-dwarf-plane...

https://www.washington.edu/news/2026/10/27/rubin-observatory...

> ED138 joins the rapidly growing sample of solar system objects discovered by Rubin since it began collecting early data in preparation for the Legacy Survey of Space and Time (LSST), which began in June 2026. In April, before LSST formally began, the Rubin solar system team announced observations of over 11,000 new asteroids, which included roughly 380 new TNOs. At the time, the team called this large submission “the tip of the iceberg” and expressed their excitement for the discoveries to come once LSST began. With the discovery of ED138, those hopes are coming to fruition.

My point was that the LSST survey was looking in those areas as part of its "mapping the Milky Way"

https://rubinobservatory.org/explore/how-rubin-works/lsst

Another recent discovery from Rubin - https://www.washington.edu/news/2026/11/05/rubin-observatory...

You can see that it is looking in those dense starfield areas.

https://rubinobservatory.org/gallery/collections/news-images... is where Rubin detected 12,700 new asteroids... and ED138 is in that part of the sky where Rubin was looking.

Pluto has a 248 year orbit... which is close to the 282 years for ED138. 100 years ago, maybe Tombaugh would have found ED138 that if he was looking in that part of the sky.

https://dahlend.github.io/ketev/#t=1930-02-18.717&sel=2026%2...

In 1925, ED138 was crossing Pluto's orbit (and closer to Earth than Pluto was).

Tangential, but what was that job? Sounds interesting.

Worked at caltech on the Near Earth Object Surveyor (NEO Surveyor) space telescope building orbital simulation tools.

That is a great little app. Thanks for sharing!

Thanks!

You can also turn on the known asteroid population:

https://dahlend.github.io/ketev/#t=2026-11-12.9717&sel=2026%...

Everything runs in the browser, served as a static github pages so I don't have to think about hosting or anything.

I've always only ever seen diagrams of the Jupiter Trojans from a top down perspective so I never realized how much they stretched beyond the orbital plane of the solar system.

Do you know why they stretch so up and down relative to Jupiter? Is that sort 3d distribution shape typical for L4 and L5 Lagrangian points, and it's just amplified by the size of Jupiter or is there something else at play there?

The Lagrange points are more like "regions" than points in reality. There is some complicated math you can do to work it out, but typically numerical stuff is a bit more reliable once you start to include the rest of the planets, the analytic theory gets pretty complicated the more bodies you include.

The trojans that you see there sort of do a little dance when you plot them in the rotating frame of Jupiter (more technical term is librate). The size of the region has to do with the mass of the parent body, since jupiter is so big, the capturing region is pretty large. Technically there are other trojans around some other planets, but most of them are not long term stable like jupiter is, mainly because jupiter is just big.

Yeah I knew they were regions more than points, I just sort of envisioned them as something more in the same of a tapered tail than something so tall compared the diameter of Jupiter.

I'd like to take the time to tell you that I really appreciate your contributions to this site. I'm always excited when there's a post about asteroids or something similarly sized in the solar system because I know that you'll post about it more often than not.

I've taken a course on the geology of the solar system and a course on exoplanet detection but I definitely consider myself a layman in this field. I've always had a particular fascination with these small tumbling rocks in our solar system so it's always a pleasure to see you talk about them and your work.

Thanks!

Here is a fun comet orbit for you: https://dahlend.github.io/ketev/#t=2018-02-08.9717&sel=P/202...

This guy had a close encounter with saturn in 2018 and his orbit dramatically changed. At the time he was likely a very cold object that had frozen volatile material (usually water and CO/CO2), The PANSTARRS telescope found him in 2023 after he started giving off material and becoming a comet.

Because he came so close to saturn, it is likely that the estimate of the orbit before this is not super precise, as orbital mechanics is a chaotic thing and small changes of initial conditions become huge changes later.

How do I enable asteroids from the UI? It looks like the information is packed into that `v` param somehow?

Yeah its not the most user friendly, go into the filters tab and check the numbered and unnumbered check boxes.

Did you intend to recommend 2688 Halley in the suggestions over 1P/Halley?

Hah, no that's a mistake. I really need to update that list anyways, there are more interesting orbits.

Thank you for an awesome app! It got me to learn the difference between 2688 Halley and 1P/Halley :)

That website is cool as

It's not great on mobile, but totally works!

The only thing that bothered me is the sidebar.

it's interesting the further the planets are the more off level their orbit is, is that because most of the planet creation chaos was happening near the sun?

It requires less delta-V to create a large change in inclination when the object is far from the Sun, because the orbital speed in a more or less circular orbit varies as (orbital radius)^(-1/2).

Yes, imagine a highly elliptical orbit and you've just reached the furthest point , like the roller coaster at the top of the hill, almost stationary. At that point you could pretty much boost the object in any direction you wanted, and it would then assume that orbit.

Yes. In that situation, where the perihelion is at the minimum tolerable distance from the Sun, the speed at apohelion is proportional to 1/(distance to sun) (this follows from conservation of angular momentum).

My first thought was 'where is New Horizons?'

Is that an egui app?

Yes its egui. I know nothing of UI stuff, I am more on the "make math go fast" side of the programming spectrum, and less on the pretty button side.

It looks like its orbit is actually within the orbit of Pluto at one point, and at times, the two bodies could come within a very small distance of each other. Wouldn't this disrupt one or the other, possibly throwing them off of their orbits?

Part of why Pluto was demoted is it's so small it doesn't effectively clear it's own orbit. Orbits can look close here but with how small Pluto is it's gravity would barely affect this dwarf planet. It's also possible they've only been at their closest approach a handful of times in their entire life.

It would help on mobile if you could you make left panel dismissable / reappearable so that the main rendered animation is visible by default

I've built a similar app with the same sources, it works pretty well on mobile: https://spacemap.co/s/54667839/2026%20ED138?at=now,-2.48520,...

Is this really a candidate for planet X.

I thought Planet X was supposed to be calculated to be several earth masses, not a dwarf planet.

Ohh, I love this. I think I need to re-read The Expanse and use that as a reference. Thank you for making it!

Sadly this site is not usable on mobile

it worked for me, you can drag the sidebar to make it smaller.

but it's not great for mobile

Reply on news.ycombinator.com