Minor Planet Electronic Circular: https://minorplanetcenter.net/mpec/K25/K25N12.html
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
Judging by how humanity didn't see any of those for millennia and now three in just several years, I can propose two hypotheses:
1. Astronomers became good enough to notice them 2. These rocks are first in an incoming flood of such objects, the Universe decided to destroy humanity.
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.
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"
I love this. But I can't help imagining the conversation on some remote South Pacific island going like this:
"Third cargo chest discovered"
"Maybe they've been sailing by here already for a long time and we just didn't notice."
> 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.
Actually we’re in a surprisingly sparse area of the galaxy, a giant hole in the galaxy created by one (or more) supernova.
Get ready for the, uh, Latter Day Late Heavy Bombardment!
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.
It's not "the Universe"; it's an alien race that wants to destroy us before we become a threat to them.
We are a much bigger threat to ourselves.
Yep, the best thing for a race that is (rightfully) worried about our aggressiveness is to wait it out.
Came here to say that. Best to just wait and let history take its course.
3. After we found the first one by chance we started looking for more objects outside the solar system's orbital plane
This object is near the solar system's orbital plane - far closer than Halley's comet, for example.
People have searched off the orbital plane for a long time, if only to find new comets.
This object was found by ATLAS, the Asteroid Terrestrial-impact Last Alert System. The project goal is to identify near-earth asteroids, evaluate the risk they might impact the Earth, and alert others if impact is predicted.
The project started in 2015, two years before ʻOumuamua. It was not made specifically to find interstellar objects transiting the solar system.
In a thread elsewhere I saw "Interstellar Objects in the Solar System: 1. Isotropic Kinematics from the Gaia Early Data Release 3" (https://arxiv.org/pdf/2103.03289) mentioned.
In there, one estimate of the number of these objects is
Nisc <~ 7.2 × 10−5 AU−3
The first two were used up, empty deceleration stages of a giant alien spaceship, discarded during interstellar cruise while the rest of the assembly kept burning for its years long deceleration from relativistic speeds. This is the main ship.
I am assuming with that the newly commissioned Vera Rubin telescope should start finding a lot more of these.
If this new 8m diameter telescope already provides us with so many new discoveries then I can't wait until the ELT with 39m diameter goes online.
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.
The more interstellar objects we find that resemble comets, the weirder Oumuamua is.
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.
I really hope someone sends a probe to catch Omaumau. When Starship is flying regularly it should be doable, just barely.
The Ramans do everything in threes.
Thank you! Finally a good Rama reference in the wild.
The great filter: light years of travel needed by detection probes.
Are we going to be able to get a close look at this?
I know nothing about this type of data; what does it mean and how can it be interpreted as an object ?
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.
They’re always coming through.
The solar system is an interstellar highway.
Chariots Of The Gods, man.
But seriously, why would interstellar objects come towards our solar system?
It seems strange. Does gravity do that?
If there’s two within ten years then there has to be a veritable swarm of these things traveling between the stars - is that right or wrong?
We updated the URL to the ABC news report as it's more understandable to lay people, at least those like me. If someone finds a better report, let us know and we'll be happy to update it.
The original URL was https://minorplanetcenter.net/mpec/K25/K25N12.html, which I've included in the header.
Don't look up
Ahhhhhh!!!!!!!!!!!
[flagged]
Closest approach will be October 29, 2025. It’s currently passing Jupiter. 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
I know it’s incredibly, vanishingly unlikely but what would happen if an object with these characteristics smacked into Earth?
The end, unless you're a small proto-mammal ;).
An object (depending on consistency) of about 100m is enough to wipe out a city and do enough damage to the environment. Something of 8-20km is in the same category as what wiped out the dinosaurs (10-15km).
8-22km at interstellar speeds? Probably total extinction level.
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.
Would be wild if a sufficiently large object with a lot of water and organic molecules hit Mars, ejected a lot of material in to Mars’ orbit to then go on to form a sufficiently large moon that tidally massaged Mars’ core to cause a dynamo to generate a sufficiently strong magnetic field to…
Terraform Mars!
in a somewhat related story, I was on a beach in Costa Rica last week, watching some spider monkeys in a palm tree trying to whack open small nuts. Just then, an American family walked up the beach with two teenage boys. They didn't notice the monkeys I was watching. But one of the boys grabbed a coconut off the sand and became determined to break it open with a rock in front of his parents. So watching the monkeys and the boy simultaneously, I had the distinct feeling of how slowly evolutionary, let alone geological, processes actually move.
Haha, cool, that gave me a chuckle :)
“We'll be saying a big hello to all intelligent lifeforms everywhere and to everyone else out there, the secret is to bang the rocks together, guys.” - The Hitchhikers Guige to the Galaxy, Douglas Adams
What is easier? Not mess up this planet, or Terraform Mars?
[delayed]
You don't need a magnetic field to terraform Mars, it can hold onto an atmosphere without it for 100M years.
Planetary magnetic field only weakly protects against cosmic rays (extra-solar origin).
A thick enough atmosphere will stop pretty much all the charged particles from the normal solar radiation.
If it would be so bad, Earth's polar regions (experiencing aurora borealis) would be inhabitable too. Earth's magnetic field is not magically neutralizing all charged particles from the Sun, just diverts them (some maybe away, but many simply towards poles).
And clearly even our mag field (and Sun's heliosphere) is not enough to shield us from those crazy cosmic rays.
Assuming it’s at the upper range of the size estimate above, and of average rocky density, the kinetic energy of the impact would be something like a 10 billion megaton nuke.
If we could steer it to hit one of Mars’s poles, it might do a bit of terraforming for us!
Where did my math go wrong? I got about 50,000 megatons. Assuming the high-end of 22km and a rocky/metallic density of 5000 kg/cubic meter (and assuming it's a cube):
If it's an icy comet then the density is more like 500 kg/cubic meter, or 1/10th that number.My mistaken use of m/s instead of km/s, in a squared term, indeed gives a HUGE difference.
Thanks!
In light of the error in the parent comments math, I retract my previous comment and substitute the following bit of awkward silence:
…
Yes, that was my error - thanks!
I would recommend staying on Earth...
Absolutely nothing. Way too small and slow.
What planets is it passing between?
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.
Huh. It looks like on 10/2 it will make its closest pass to a planet, Mars, and on that date it also is in a straight line with Mars, Mercury and the sun, while Earth and Venus are roughly opposite each other. Do you know if this sim accounts for solar or martian gravity diverting its trajectory?
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.
> It is almost on the plane of the solar system, not very inclined.
Is this also random chance or is there a reason why it's so close to the plane of the solar system?
We're going to see a lot more of these in the next couple of years due to the new Vera C Rubin observatory.
I would expect most visitors would come from the galactic plane.
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?
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.