Astronomers discover 3I/ATLAS – Third interstellar object to visit Solar System (opens in new tab)

Closest approach will be October 29, 2025. It’s currently passing Jupiter’s orbit. I’m amazed that even at this speed it will take that long to get here.

“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.” ~Douglas Adams

Thanks for sharing your expertise! What really bends my mind is the relative speeds involved. Reddit's /r/space has a great visual[1] which depicts it as basically going straight through our solar system, only bending slightly as it passes Sol. This is only possible if the object moving at 68 km/s is also moving sideways at 230 km/s so as to match our galactic orbit, and moving up at a mind-boggling 600 km/s (relative to CMB). This is all basic stuff of course, but something about having the object actually pass by us is making it more real than usual...

Hell, maybe it's only orbiting the galaxy at a leisurely 160 km/s, and from its perspective we're a spinning disc of chaos zipping past it for the first time in a few million years! I don't even know how I would start to analyze its orientation in relation to the galactic center, but I'll be keeping this as my little "headcannon" until proven wrong, that's for sure.

[1] https://www.reddit.com/r/space/comments/1lpw4as/new_interste...

From the simulation you linked looks like it is passing closeish to the Mars... but I do know that space is big. However, I am curious of what would happen if an object of this magnitude hit mars at 90km/s.

From the first link I get:

"specified object was not found"

What do you mean by 'active' here - has a plume?

Thanks for sharing this info. Does "eccentricity" refer to the orbit, or the shape of the object?

For ‘Oumuamua in 2017, some method was used to determine its shape, which is (apparently) remarkably elongated. Is it possible to determine the elongation of the new object?

https://science.nasa.gov/solar-system/comets/oumuamua/

Are you able to calculate whether, by any chance, it will come close to any of the NASA probes around Jupiter, Mars, Venus, etc...? What is its closest approach to the JWST?

> Source: Working on my PhD in orbital dynamics and formerly wrote the asteroid simulation code used on several NASA missions:

This is one of the big reasons I love HN

I know it’s incredibly, vanishingly unlikely but what would happen if an object with these characteristics smacked into Earth?

What planets is it passing between?

Getting a "specified object not found" on the orbit viewer.

Vera Rubin just came online, will will start to do surveys of the entire sky every 3 nights, which makes spotting stuff like this easier.

https://youtu.be/X3N-DjVXh44

so we are probably gonna notice a lot more of them

It's 1. A combination of better telescopes and GPU accelerated algorithms for picking out moving objects.

hah! Yeah the title "Third Interstellar Object Discovered" needs to be changed to be more like "Third Discovery of an Interstellar Object"

> These rocks are first in an incoming flood of such objects

When ʻOumuamua flew past, we should have noticed it was a passive sensor drone. Now it is too late.

I get that you're joking, but I wonder if it could just be that we happen to be passing through some sort of interstellar debris cloud.

We hadn't the means to discover them for most of the last millennia, so now being good enough is obvious. But the question is why now, and not 10 or 20 years ago. It might be that we had the ability for a longer time already, but it just never "clicked" until now to recognize them. It is also possible that we really just got good enough recently. Or even that until now, there really were none in the last decade we could find, and we are just lucky(?) that now more are coming our way.

We might know this better in the next years, depending on whether there will now be an explosion of dozen and dozens of new interstellar objects discovered, or not. It might be another rush, like with exoplanets and local dwarf-planets.

I believe #1 is true; but not #2. It's just that those rocks are more common than we thought. And we thought they were uncommon because we weren't able to spot them... yet.

We don't know if they're all rocks or not yet.

It's not "the Universe"; it's an alien race that wants to destroy us before we become a threat to them.

3. After we found the first one by chance we started looking for more objects outside the solar system's orbital plane

It's built to find all of them, above a certain brightness.

We genuinely don't any idea how many it will be, so I'm hoping for a lot!

Imagine when we can get real sample material from other solar systems!

expand this into a sci Fi novella please

Maybe. I think it's more likely that an alien probe - assuming there are aliens and they fly probes - would be the size of a cubesat, and we wouldn't even notice it.

Perhaps Oumuamua was the mothership and the solar system is now swarming with cubesats we're not noticing.

The Ramans do everything in threes.

I really hope someone sends a probe to catch Omaumau. When Starship is flying regularly it should be doable, just barely.

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.

tbf, Omuamua was given denomination 1I in 2017 - so it's not "reality coincided with imaginary naming", but simply "book followed real life"

If we're just talking about interstellar objects, and assuming a decent lead time (not oh hey it's going to hit in 3 days), it's probably easier to prevent it from hitting us since it's most likely just passing through. You'd only need to give it a small enough nudge to have it miss a smidge. That's something we're more than capable now of doing, and have done.

If this object were coming straight for Earth there would be pretty much nothing we could do to avoid a collision. Luckily the chances of such a collision are enormously small. We are fortunately bringing more resources on line to find such objects sooner.

ELT will not discover many new objects, it's built to do deeper followup observations of known targets. On the other hand, Vera Rubin was designed to be a survey telescope, repeatedly imaging the entire night sky to discover new objects. It will not do targeted observations, or at least very few.

Given it's passing retrograde (is that even the right way to say that?), would that make it easier to catch up and intercept?

Assuming you don't want to do anything but fly by or smash into it

Not really, the sun will be in a rather inconvenient position.

Objects can get flung out of solar systems when they pass close to large objects. Similar to how spacecraft get gravity assists.

A very rough calculation would suggested that the cylinder that goes from our solar system to Proxima Centauri contains 5000 similarly sized objects moving at the same speed:

1 object crossing the solar system plane every 5 years at 60km/s

+

Proxima Centauri is approximately 5 light years away

=>

there are `speed of light / 60km/s` objects in the cylinder.

> But seriously, why would interstellar objects come towards our solar system?

Why wouldn't they?

The "popular" understanding might even be "it's aliens!". Let me pull my elitist card, but I think it's irresponsible for journalists to use the word "visit", because it implies a thinking creature performing an action. God knows this planet has too many morons who'll see this headline and understand it to be "definitely aliens!"...

When you're dealing with objects as small as this, their weight and size is essentially mathematically irrelevant. It doesn't have any type of propulsion, so we know that unless it collides with something along its trajectory, it will keep following the same course. We know the mass and diameter of the celestial bodies that the object will be traveling near, so we can calculate how those bodies will affect its trajectory. As one of the top comments said: it has a very high eccentricity, which means it's traveling along a path that forms a very elongated, open hyperbole, so it won't come close enough to the sun to be affected by its gravitational pull if it continues to follow its current trajectory.

Ahhhhhh!!!!!!!!!!!