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.
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
TrainedMonkey · 3h ago
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.
nandomrumber · 2h ago
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!
noduerme · 1h ago
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.
nandomrumber · 1h ago
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
WithinReason · 2h ago
You don't need a magnetic field to terraform Mars, it can hold onto an atmosphere without it for 100M years.
nandomrumber · 1h ago
Without a magnetic field, isn’t the surface of Mars subject to sterilising radiation from Sol?
cyberax · 1h ago
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.
jajko · 1h ago
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.
jl6 · 2h ago
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!
eesmith · 2h ago
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):
kinetic energy = 1/2 m v**2 = 1/2 * size * density * v**2
= 1/2 *(22000 m)**3 * (5000 kg/m**3) * (90 m/s)**2 / (4.184E15 J/megaton)
= 52,000 megaton
If it's an icy comet then the density is more like 500 kg/cubic meter, or 1/10th that number.
perihelions · 2h ago
I can not confirm this; the parent calculation is the correct one. I can't immediately find what your error was. (edit: It's your [km/s]—you wrote [m/s] by mistake).
(let* ((ρ ([g (cm -3)] 5))
(d ([km] 22))
(m (* ρ (expt d 3)))
(v ([km (s -1)] 90))
(ke (* 1/2 m (expt v 2)))
(kg-tnt ([J (kg -1)] 4.2e6)))
(values (/ ke kg-tnt)
(as [megaton] (/ ke kg-tnt))))
5.133857142857142e19 [KG]
5.133857142857143e10 [MEGATON]
eesmith · 44m ago
My mistaken use of m/s instead of km/s, in a squared term, indeed gives a HUGE difference.
Thanks!
nandomrumber · 2h ago
1040 x more energy that the Tsar Bomba.
Or 5-ish Tsar Bomba per country on Earth.
Or 3466 Hiroshima nukes.
Or 17 Hiroshima nukes per country.
nandomrumber · 2h ago
In light of the error in the parent comments math, I retract my previous comment and substitute the following bit of awkward silence:
…
defrost · 1h ago
We all make mistakes, as the Dalek said climbing off the dustbin.
FWiW .. here's mine (or is it?)
One Tsar Bomba ~ 50 megatonne.
One Hiroshima bomb ~ 15 kilotonne.
Every time I see your username I can’t help but say it in my mind as Defrost Kelly, some kind of frozen Dr. Leonard "Bones" McCoy
ars · 2h ago
90 m/s?
Way too slow, it's more like 70km/s (or 90) - seems you left out a k.
eesmith · 43m ago
Yes, that was my error - thanks!
ddahlen · 3h ago
I would recommend staying on Earth...
ReptileMan · 2h ago
Absolutely nothing. Way too small and slow.
noduerme · 3h ago
What planets is it passing between?
ddahlen · 3h ago
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.
noduerme · 2h ago
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?
ddahlen · 15m ago
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.
Teever · 3h ago
> 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?
ddahlen · 3h ago
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.
sgt101 · 1h ago
We're going to see a lot more of these in the next couple of years due to the new Vera C Rubin observatory.
JumpCrisscross · 1h ago
Also the ELT [1], I believe. (Both come online this year.)
Good question, especially given the plane of our solar system is almost orthogonal to the greater plane of the Milky Way galaxy that contains us.
belter · 2h ago
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?
ddahlen · 2h ago
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.
ordu · 4h ago
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.
elchananHaas · 3h ago
It's 1. A combination of better telescopes and GPU accelerated algorithms for picking out moving objects.
em3rgent0rdr · 4h ago
hah! Yeah the title "Third Interstellar Object Discovered" needs to be changed to be more like "Third Discovery of an Interstellar Object"
noduerme · 3h ago
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."
9dev · 3h ago
> 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.
No comments yet
dotnet00 · 3h ago
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.
eb0la · 2h ago
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.
shiroiuma · 3h ago
It's not "the Universe"; it's an alien race that wants to destroy us before we become a threat to them.
belter · 2h ago
We are a much bigger threat to ourselves.
phatskat · 2h ago
Yep, the best thing for a race that is (rightfully) worried about our aggressiveness is to wait it out.
lynx97 · 2h ago
Came here to say that. Best to just wait and let history take its course.
nandomrumber · 1h ago
Or launch an attack fleet, only to later, due to an error in a scaling factor, have the entire fleet unknowingly swallowed by a small dog.
haiku2077 · 4h ago
3. After we found the first one by chance we started looking for more objects outside the solar system's orbital plane
eesmith · 2h ago
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.
zeristor · 3h ago
I am assuming with that the newly commissioned Vera Rubin telescope should start finding a lot more of these.
rjinman · 55m ago
The more interstellar objects we find that resemble comets, the weirder Oumuamua is.
LeoPanthera · 34m ago
The Ramans do everything in threes.
jerpint · 3h ago
I know nothing about this type of data; what does it mean and how can it be interpreted as an object ?
ddahlen · 3h ago
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.
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.
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
Terraform Mars!
“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
A thick enough atmosphere will stop pretty much all the charged particles from the normal solar radiation.
And clearly even our mag field (and Sun's heliosphere) is not enough to shield us from those crazy cosmic rays.
If we could steer it to hit one of Mars’s poles, it might do a bit of terraforming for us!
Thanks!
Or 5-ish Tsar Bomba per country on Earth.
Or 3466 Hiroshima nukes.
Or 17 Hiroshima nukes per country.
…
FWiW .. here's mine (or is it?)
One Tsar Bomba ~ 50 megatonne. One Hiroshima bomb ~ 15 kilotonne.
One Tsar Bomba ~ 50,000 / 15 ~ 3,333 Hiroshima bombs.
1,040 x Tsar Bomba ~ 3,466,667 Hiroshima bombs.
Every time I see your username I can’t help but say it in my mind as Defrost Kelly, some kind of frozen Dr. Leonard "Bones" McCoy
Way too slow, it's more like 70km/s (or 90) - seems you left out a k.
I linked an orbit viewer above if you want to look.
I did a full proper n-body integration and it is not visually different than this.
Is this also random chance or is there a reason why it's so close to the plane of the solar system?
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.
[1] https://en.m.wikipedia.org/wiki/Extremely_Large_Telescope
If it is an inactive rock, then we will not see it as any more than a point of light during its visit.
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.
"Third cargo chest discovered"
"Maybe they've been sailing by here already for a long time and we just didn't notice."
When ʻOumuamua flew past, we should have noticed it was a passive sensor drone. Now it is too late.
No comments yet
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.
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.
The original URL was https://minorplanetcenter.net/mpec/K25/K25N12.html, which I've included in the header.