ddahlen

It is neat to see some of the old work done in the field, this looks like a pretty classic treatment of the topic. It looks like they were using a fourth-order Runge-Kutta integrator, which would likely limit long term integrations accuracy (though looks sufficient for their use case). Many algorithms I have seen typically use much higher order integration methods to beat down the accumulation of numerical error.

Source: Working on my PhD in orbital mechanics of asteroids/comets, here are my open source (python/rust) orbital integration tools: https://github.com/dahlend/kete

Final edits of a paper at the moment, aim to submit next week. Perturbers are easy to add, though a little poorly documented at the moment. Additional physics right now are J2 of jupiter/sun/earth, and GR corrections for the sun and jupiter.

Biggest speed gain is that I have a custom SPICE reader that is multi-core friendly (I re-implemented a lot of the SPICE standard in rust), and it is used as the source for planet positions. Being able to skip planet integration leads to massive speedups.

I wrote a custom implementation of the Radau integrator, its been heavily modified. I have a lot of additional physics, it supports the non-gravitational models that JPL Horizons defaults to, so diurnal yarkovsky at least. I've been using it to study dust and small object dynamics, as they get pushed around by the sun a lot.

It does an OK job for impactors, but the integrator is tuned heavily for performance, and the tolerance defaults are not great for impactors.

I match jpl horizons for apophis to a few km, they have a lot more intense earth gravitational model then I care to implement, and by default I only include the 5 heaviest main belt asteroids, they have many more. That was the sweet spot for accuracy vs speed for me, overall accuracy goal is less than a few km over a decade.

The goal is to be able to handle the huge influx of new asteroids that the catalog will have due to LSST and eventually NEO Surveyor (which I worked on for 3 years). Most systems I know have been throwing hardware at the problem, I tried to make fast and efficient enough software that we can use it on a laptop for 5-10 million asteroids.

Different goals, kete is meant to be aimed more toward observers and telescope data processing, all asteroids and comets at once on a laptop. Short term analysis (<100 years) and speed are the priority.

Oort cloud comets are so distant that they are only weakly gravitationally bound to the solar system. When they come in and we see them, they have enough energy to go back out to the extreme distances. Minor nudges from the big planets are enough to cause them to become ejected from the solar system (ecc>1). This can lead to the whole "one and done" thing.

Eccentricity!

You can approximate the orbits of basically everything in the solar system using 2-body mechanics (IE, ignore the planets). If you do this you get orbits which are elliptical (eccentricity <1), parabolic (eccentricity = 1), or hyperbolic (eccentricity>1).

If the object has an eccentricity above 1, its not bound to the solar system.

Many long period comets have eccentricity hovering near 1, often these long period comets will be on their first pass (sometimes only pass) through the solar system. These comets though usually dont get much above eccentricity of 1. The 3 interstellars we have spotted have had like 1.2 or bigger. This one is above eccentricity 6! Its moving fast.

Edit: I have heard that when the first interstellar was found it actually broke a lot of peoples code, as it was common to hard code limits to allowed eccentricities (or simply not support ecc>1 at all).

I'm one of those astronomers! I'm working on my PhD in orbital dynamics.

A lot of people are requesting discretionary time on telescopes trying to get observations in. The orbit will put us on the other side of the sun when 3I is nearest the sun in october, we can see it now and after it comes back out from behind the sun.

Unfortunately, right now the it is in a very crowded star field (IE, its close to the galactic plane, lots of stars in the background).

If you are interested in orbital dynamics, I have an open source rust/python package for accurate orbital calculations of asteroids/comets:

https://github.com/dahlend/kete

This orbit visualization uses a simple 2 body approximation, so only the sun. This is because unless an object has a VERY close approach to a planet the two body approximation is more then enough for this style of visualization.

I did a full proper n-body integration and it is not visually different than this.

The closest it will come is Mars, but when I say close these are quite literally astronomical distances, about 0.2 au from Mars. This is about 75x further than the moon is from the Earth.

If it is an inactive rock, then we will not see it as any more than a point of light during its visit.

I would recommend staying on Earth...

It is also a factor of where our surveys look on the sky. A lot of asteroid surveys have biases to look at the plane of our solar system (since this is where a lot of asteroids are).

It is probably random chance, however there may be some biases from where they come from on the sky (I know people who work on that, but I don't know much about it).

N=3 does not provide very robust statistics yet, give us another decade or two.

This is an announcement from the Minor Planet Center (MPC). They are the official international clearing house for observations of solar system objects.

The top indicates that the object has two names (this is common): 3I/ATLAS = C/2025 N1 (ATLAS)

ATLAS was the telescope that made the discovery.

The list of data are individual observations of the object by different telescopes. This observation format has been in use for a long time, but is being phased out. A row is meant to fit on a single punch card...

These observations are then used to calculate orbits, the MPC calculates the orbit as well, but this list of observations is also ingested by JPL and their Horizons service.

It is inside jupiter's orbit now, it will come inside Mars for a time. It is almost on the plane of the solar system, not very inclined.

I linked an orbit viewer above if you want to look.

This one is coming in fast, it has an eccentricity of over 6 with the current fits. For point of reference, 1I and 2I have eccentricities of 1.2 and 3.3.

Right now it is mostly just a point on the sky, it is difficult to tell if it is active (like a comet) yet. If it is not active, IE: asteroid like, then the current observations put it somewhere between 8-22km in diameter (this depends on the albedo of the surface). From what we know, we would expect it to likely be made up of darker material meaning given that range of diameters it is more likely to be on the larger end. However if it is active, then the dust coming off can make it appear much larger than it is. As it comes in closer to the sun and starts to warm up it may become active (or more active if its already doing stuff).

It will not pass particularly close to any planet. It will be closest to the sun just before Halloween this year at 1.35 au, moving at 68 km/s (earth orbits at 29-30 km/s). It is also retrograde (IE, it is moving in the opposite direction of planetary motion), for an interstellar object this is basically random chance that this is the case.

Link to an orbit viewer: https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3I&vi...

The next couple of weeks will be interesting for a bunch of people I know.

Source: Working on my PhD in orbital dynamics and formerly wrote the asteroid simulation code used on several NASA missions: https://github.com/dahlend/kete

I posted a couple of months ago:

https://github.com/dahlend/kete

Research grade orbit calculations for asteroids and comets (rust/python).

I began working on this when I worked at caltech on the Near Earth Object Surveyor telescope project. It was originally designed to predict the location of asteroids in images. I have moved to germany for a PhD. I am actively extending this code for my phd research (comet dust dynamics).

Its made to compute the entire asteroid catalog at once on a laptop. There is always a tradeoff between accuracy and speed, this is tuned to be <10km over a decade for basically the entire catalog, but giving up that small amount of accuracy gained a lot of speed.

Example, here is the close approach of Apophis in 2029:

https://dahlend.github.io/kete/auto_examples/plot_close_appr...

As I said, just an order of magnitude estimate for many non-adaptive optics telescopes.

The atmosphere is always an issue, we can correct for many of the effects using adaptive optics, but there are always limits. The advantage you get from going bigger on the ground is that you are making a bigger "bucket" to put photons in. More photons = fainter objects are visible, this is the motivation for projects like:

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

Typically for non-adaptive optics telescope the atmosphere will limit you to the scale of about an arcsecond. Meaning objects which take up less than an arcsecond of the sky will appear as points. Adaptive optics telescopes however have much better resolving power.

I have been working in astronomy for a few years now and I recently have gone back to school for a PhD in orbital dynamics.

Rubin is going to make a big difference in our knowledge of the asteroid belt, it will likely more than triple the size of our known catalog of asteroids. Its actually somewhat difficult to know exactly how much it will increase our knowledge. The bigger the telescope we build, the fainter the asteroids we see. The difficulty is that while we can make a pretty educated guess as to how many smaller ones there are, this is such a jump that the error bars on that guess is quite large. I am quite excited to see how the catalog of asteroids changes, I expect we will be finding a LOT of smaller rocks near the Earth.

Asteroids have a broad range of albedo, basically the brightness of the surface can vary from the blackest coal (like 3-5% of the light reflecting) to concrete (up to about 50%). All visible range telescopes will be susceptible to a bias in their observations, since a big black rock will be as bright as a smaller paler rock. We know that the asteroid belt favors the dark material.

In a couple of years, the Near Earth Object Surveyor (NEOS) space telescope will launch. NEOS is an IR telescope and will not have the same albedo bias. The trade off is that it will measure the black body radiation, meaning asteroids have to be nearer the sun. Broadly these are very complementary surveys, Rubin will be fantastic for filling out the main belt, and NEO Surveyor will do a great job on our neighborhood.

Source: I worked at Caltech on NEOS, I wrote the code they use to predict known asteroid orbits:

https://github.com/dahlend/kete

Edit: I failed to mention that Rubin is a big deal for a lot of time-domain astronomy, I'm just being selfish talking about asteroids only.

I got a bit too excited with this one, this is may not be a full on dwarf planet, but it is a very large object. There are only a small number (about 10-20) objects in our solar system of this size. Its the first big one we have found in a number of years.

If you want to view the orbit:

https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2017%...

Depends on the albedo, if the H magnitude is a good measurement, then it is probably between 300-700km. These are rough bounds, its highly dependent on how reflective it's surface is (albedo).

With an orbit somewhere around 28k years, it reached perihelion in about 1931, at 45 au from the Sun.

The minor planet center is the clearing house of observations of objects in our solar system. They have announced a new dwarf planet today.

This object appears to be in a very eccentric orbit (0.948), and with an H magnitude of 3.55, so it is likely hundreds of km in diameter. Ceres for reference has a H magnitude of 3.33 (smaller H is bigger diameter).

If you want to know what H means: https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_Syste...

I have been in and out of the academic world my entire career. I have worked as a programmer/engineer for two universities and a national lab, and worked at a startup founded by some professors. There is huge uncertainty with the people whom I have worked with, nobody seems to be sure what is going to happen, but it feels like it wont be good. Hiring freezes, international graduate students receiving emails to self deport, and at my last institute many people's funding now no longer supports travel for attend conferences (a key part of science!).

One of the interesting pieces of science that I think a lot of people don't think about is strategic investment. At one point I was paid from a government grant to do high power laser research. Of course there were goals for the grant, but the grant was specifically funded so that the US didn't lose the knowledge of HOW to build lasers. The optics field for example is small, and there are not that many professors. It is an old field, most of the real research is in the private industry. However what happens if a company goes out of business? If we don't have public institutions with the knowledge to train new generations then information can and will be lost.

Basically all observations of solar system objects besides the big planets are going to be unresolved point sources. IE: We don't have telescopes which can resolve most objects into an image. An example, Hubble famously had to image a ton to get a grainy, ~12 pixel approximation of Pluto. We can do a lot with measurements of points, even reconstruct 3d models if we have enough data.

Resolving power is related to the PSF (Point Spread Function) size. The PSF is the image on your detector if you have an infinitely small point source. A quick google search says that DECam has a PSF of at least an arcsecond (atmosphere is probably causing issues for that). Which means anything smaller than an arcsecond is going to be unresolvable.

However, you still want pixels smaller than your PSF, since PSFs are typically gaussian-ish, having a bunch of measurements within the gaussian allows you to estimate the center accurately. This is vital for Astrometry (the measurement of position).

2 big reasons, first is that wobbles which we normally observe require that the star move enough to be detected on a shorter time scale. IE: if the orbit takes 100 years and we look twice in 5 years, the planet will have only moved 5% of an orbit and the wobble will be near 0. Second is the less mass and further the planet is away, the less noticeable the wobble. Something at 500 au is going to produce no measurable wobble in our lifetime.

Most images are registered by finding the location of known stars from a high resolution catalog such as GAIA. So you fit centroids of all stars in an image, then do a search of Gaia sources in that location and do some sort of linear or higher order polynomial mapping of pixel space to the celestial sphere reference coordinates ICRF.

Astrometry.net is a service that does an approximate version of this on the web.

I am glossing over many details here, but this is roughly what happens.

Thank you for the offer! Unfortunately the PhD has already sunk its claws in. I should have some flashy stuff to show off in a 2-3 months (I have a conference talk coming I have to prepare material for).

I've never really dabbled in youtube. I have several projects/papers I am working on using this code, I have thought about writing some blog posts as I publish those. But a PhD is going to be a major time sink, we will see what happens.

I am about to begin a PhD in astronomy. Until last month I was working at Caltech for 3 years on code which calculates orbits of asteroids to high precision. This code is being used on several NASA telescopes now to predict when they will image known asteroids (NEO Surveyor, SphereX, maybe Roman eventually). I was allowed to open source it and I am planning on making it the basis of my PhD research:

https://github.com/dahlend/kete

It can predict the location of the entire catalog of known asteroids to generally within the uncertainty of our knowledge of the orbits. Its core is written in rust, with a python frontend.

I cannot speak for the community, I don't have a very broad contact list for this sort of thing. Among the few people I know this has definitely drummed up some interest though (there are not nearly as many people who study asteroids as the public would think). Where JWST points is a complicated process that I only have a vague understanding of, this would likely require some kind of director discretionary time (I dont even know if JWST does that).