Interstellar objects

[DanClemmensen]

Just curious.  With the three objects spotted so far, are their trajectories in any way similar or are they vastly different ?

Are you thinking of "Rendezvous with Rama"? They come in three.

Not initially, but now that you mention it 🤔

I was thinking that if they all came from the same general direction then maybe they were all the product of some ancient cataclysm like a planet killer event somewhere.  A sample retrieval mission would be awesome.  Just watch out for anything blue.

If I recall correctly, 1I/ʻOumuamua was nearly at rest relative to the average velocity of the local stars. The Solar system is moving relative to that average, so the object did not come to us. Rather, we came to it.

[jebbo]

Loeb is Harvard’s Chicken Little. An embarrassment to science, if not humanity.

When 3I was first announced, Jonathan McDowell, who works at Harvard SAO, joked on BSKY that it would only be a short time before his colleague labeled it an alien spaceship.

He wasn't the only one. Lots of my astronomer friends did likewise.

There's a pretty good thread by Jason Wright** on his claims here: https://bsky.app/profile/astrowright.bsky.social/post/3lu5z4epeh226

And he's blogged about it here: https://sites.psu.edu/astrowright/2025/07/18/avi-and-3i-atlas/

** a serious SETI/technosignatures guy

--- Tony

[jebbo]

We're starting to get results from the big glass now.

This one is from the 10.4 m GTC.

https://arxiv.org/abs/2507.12922

So, well-defined coma, rotation period around 16.8 hours, probably from the thin disc, spect4um similar to a D asteroid.

--- Tony

[Star One]

We're starting to get results from the big glass now.

This one is from the 10.4 m GTC.

https://arxiv.org/abs/2507.12922

So, well-defined coma, rotation period around 16.8 hours, probably from the thin disc, spect4um similar to a D asteroid.

--- Tony

Soon changed their minds then, there was a paper only last week that was talking about it coming from the thick disc.

[Star One]

Hubble spots interstellar invader Comet 3I/ATLAS for the first time

https://www.space.com/astronomy/asteroids/hubble-spots-interstellar-invader-comet-3i-atlas-for-the-first-time

[Star One]

3I/ATLAS News with Darryl Seligman:

[StraumliBlight]

Vera Rubin Observatory Unveils First High-Res Images of 3I/ATLAS—Captured Days Before Astronomers Knew It Existed [Jul 23]

In a well-timed coincidence, astronomers at the Rubin Observatory succeeded in capturing 3I/ATLAS in high-resolution images several days before the discovery was officially announced, offering the earliest and most detailed observations of the object to date as astronomers continue to amass data about it.

[...]

“Serendipitously, the Rubin Observatory collected imaging in the area of the sky inhabited by the object during regular commissioning activities,” the authors of the new study write. “We successfully recover object detections from Rubin visits spanning UT 2025 June 21 (10 days before discovery) to UT 2025 July 7.”

[Norm38]

This is likely a bit off topic but not sure where to put it other than a party thread.  I was thinking about Arthur C Clarke's novel The Songs of Distant Earth where the Starship Magellan is protected by a massive ice shield several km in diameter (I think?, the ship is 1km diameter).

If such a ship was coming in on a trajectory similar to Atlas/3I, (I forget how the ship was supposed to slow down), would the ice shield start to outgas with a coma and look like a comet?  As long as it was facing us I suppose.

Just an interesting visual, a starship screaming into a system glowing like a comet, but not a comet.

[Star One]

I’m posting this here as he mentions a paper proposing using one of the Mars spacecraft close to the end of their missions and using them to intercept this comet. The relevant paper  is linked directly to the pdf in the video description.

[jebbo]

There are lots of interesting discussions to be had on technosignatures and how to unequivocally detect them. But here is not the place to have them 😀

And weirdly, I don't remember that story even though I've read Clarke many many times!

--- Tony

[Star One]

Intercepting 3I/ATLAS at Its Closest Approach to Jupiter with the Rejuvenated Juno Spacecraft

The interstellar object 3I/ATLAS was discovered on July 1, 2025. It is expected to arrive at a distance of 53.6 million kilometers from Jupiter on March 16, 2026.

In a new paper (accessible here) that I wrote with the brilliant Adam Hibberd and Adam Crowl, we show that applying a thrust of 2.675 kilometers per second on September 14, 2025 can bring the Juno spacecraft from its orbit around Jupiter to intercept the path of 3I/ATLAS.

…

Our paper shows that applying a thrust of 2.6755 kilometers per second on September 9, 2025, can potentially bring the Juno spacecraft from its orbit around Jupiter to intercept the path of 3I/ATLAS.

https://avi-loeb.medium.com/intercepting-3i-atlas-at-its-closest-approach-to-jupiter-with-the-rejuvenated-juno-spacecraft-334939feca22

Direct link to pdf of paper in the article.

[flatpf]

As with all these "Let's send this spacecraft that's near the end of it's life to 3/I ATLAS"- proposals, I highly doubt these different spacecraft have the amount of fuel left to intercept 3/I as they are near the end of their lives.

[StraumliBlight]

As with all these "Let's send this spacecraft that's near the end of it's life to 3/I ATLAS"- proposals, I highly doubt these different spacecraft have the amount of fuel left to intercept 3/I as they are near the end of their lives.

Juno had 785 kg of fuel (569 kg hydrazine and 216 kg oxidizer) after the Jupiter Orbit Insertion burn in 2016, do we know how much is left?

[Comga]

As with all these "Let's send this spacecraft that's near the end of it's life to 3/I ATLAS"- proposals, I highly doubt these different spacecraft have the amount of fuel left to intercept 3/I as they are near the end of their lives.

Juno had 785 kg of fuel (569 kg hydrazine and 216 kg oxidizer) after the Jupiter Orbit Insertion burn in 2016, do we know how much is left?

According to our friend Wikipedia, Juno has a dry mass of 1593 kg
An average Isp for hydrazine bipropellant is 322 sec
Assuming that 100% of those propellants are left, that they are in exactly the ratio to be fed to the engine, and that they were to be completely combusted, the rocket equation yields 1335 m/s Delta-V, about half of the 2676 m/s Avi says would be necessary.
It's a non-starter.

And if it was possible, NASA would have 5 weeks to decide, plan, upload, and execute the burn before September 9.
That's another insurmountable obstacle.

PS  I am contemplating writing a paper on the statistical improbability of Avi NOT being an alien.
I mean, given that Israelis are about 0.1% of the world population the likelihood that the head of the Astronomy department is an Israeli is almost vanishingly small.
This is compounded by other improbabilities.
To be exhaustive, for the sake of argument, we must include among the other possibilities that he is an alien...... trying to call home.

[Norm38]

As with all these "Let's send this spacecraft that's near the end of it's life to 3/I ATLAS"- proposals, I highly doubt these different spacecraft have the amount of fuel left to intercept 3/I as they are near the end of their lives.

This is why we really need the SpaceX Starship architecture to work.  A dedicated expendable tanker/booster in LEO docks to a "departure stage" (Starship engines, tanks, payload - maybe drops its fairings?).

Send that screaming out of orbit on an intercept course, with enough prop to decelerate at intercept.

I just dream up the architecture, I'll let the engineers work out the numbers how that would actually work.

[sstli2]

Intercepting 3I/ATLAS at Its Closest Approach to Jupiter with the Rejuvenated Juno Spacecraft

The interstellar object 3I/ATLAS was discovered on July 1, 2025. It is expected to arrive at a distance of 53.6 million kilometers from Jupiter on March 16, 2026.

In a new paper (accessible here) that I wrote with the brilliant Adam Hibberd and Adam Crowl, we show that applying a thrust of 2.675 kilometers per second on September 14, 2025 can bring the Juno spacecraft from its orbit around Jupiter to intercept the path of 3I/ATLAS.

…

Our paper shows that applying a thrust of 2.6755 kilometers per second on September 9, 2025, can potentially bring the Juno spacecraft from its orbit around Jupiter to intercept the path of 3I/ATLAS.

https://avi-loeb.medium.com/intercepting-3i-atlas-at-its-closest-approach-to-jupiter-with-the-rejuvenated-juno-spacecraft-334939feca22

Direct link to pdf of paper in the article.

This paper is being widely criticized in astrophysics circles. Here's a social media thread where one of the authors responds and acknowledges that it's not actually possible, for multiple reasons: https://bsky.app/profile/adamsspaceresearch.bsky.social/post/3lv6hh66cwk27

Can we please stop giving attention to Avi Loeb? He's a charlatan.

[Blackstar]

This paper is being widely criticized in astrophysics circles. Here's a social media thread where one of the authors responds and acknowledges that it's not actually possible, for multiple reasons: https://bsky.app/profile/adamsspaceresearch.bsky.social/post/3lv6hh66cwk27

Can we please stop giving attention to Avi Loeb? He's a charlatan.

Re intercepting it--if you develop even a little bit of understanding of delta-v and the size of space (hint--it's really really big...), you realize that these things are impossible. To do an interception would require a lot of advance warning and a spacecraft that just happened to be in the right location with a lot of fuel (alternatively, launched for that purpose). It takes years to send a spacecraft to planets that are in totally predictable orbits, so shooting somewhere random on short notice is highly unlikely.

Yeah about Loeb. But he is the rare real scientist with real publications who also happens to engage with some nutty ideas. It's not like he's some total kook, and that's why he can still get some notice.

[LouScheffer]

Re intercepting it--if you develop even a little bit of understanding of delta-v and the size of space (hint--it's really really big...), you realize that these things are impossible. To do an interception would require a lot of advance warning and a spacecraft that just happened to be in the right location with a lot of fuel (alternatively, launched for that purpose).

Arthur C. Clarke got this exactly right in rendezvous with Rama.  First, they saw Rama when it was still far out, since it was big.  Then they were able to re-purpose an outer planet mission (so presumably high delta-v) for a very high speed flyby.  Then for a rendezvous, they had to take the best positioned ship (in a solar system full of ships) and even it needed to refuel using all the remaining fuel of three other ships.  Rendezvous is really hard.

Endeavor was the only spacecraft in the solar system which could possibly make a rendezvous with the intruder before it whipped round the sun and hurled itself back towards the stars. Even so, it had been necessary to rob three other ships of the Solar Survey, which were now drifting helplessly until tankers could refuel them.

And though Clarke did not provide any specifics, likely Rama was easier then 3/I, as 3/I is not merely above escape velocity, it's well above it.

[Star One]

Intercepting 3I/ATLAS at Its Closest Approach to Jupiter with the Rejuvenated Juno Spacecraft

The interstellar object 3I/ATLAS was discovered on July 1, 2025. It is expected to arrive at a distance of 53.6 million kilometers from Jupiter on March 16, 2026.

In a new paper (accessible here) that I wrote with the brilliant Adam Hibberd and Adam Crowl, we show that applying a thrust of 2.675 kilometers per second on September 14, 2025 can bring the Juno spacecraft from its orbit around Jupiter to intercept the path of 3I/ATLAS.

…

Our paper shows that applying a thrust of 2.6755 kilometers per second on September 9, 2025, can potentially bring the Juno spacecraft from its orbit around Jupiter to intercept the path of 3I/ATLAS.

https://avi-loeb.medium.com/intercepting-3i-atlas-at-its-closest-approach-to-jupiter-with-the-rejuvenated-juno-spacecraft-334939feca22

Direct link to pdf of paper in the article.

This paper is being widely criticized in astrophysics circles. Here's a social media thread where one of the authors responds and acknowledges that it's not actually possible, for multiple reasons: https://bsky.app/profile/adamsspaceresearch.bsky.social/post/3lv6hh66cwk27

Can we please stop giving attention to Avi Loeb? He's a charlatan.

No doubt you’ve been watching that video by some big name science communicator on You Tube that just does, in my view, an unfair hatchet job on him. Seemingly forgetting that yes he has out there ideas, but he’s also a serious scientist as well with published papers.

[daedalus1]

Does anyone know if Juno has 2.6 km/sec dV available?