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Interstellar Comet 3I/Atlas: What We Know Now

skyandtelescope.org

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Re: Interstellar Comet 3I/Atlas: What We Know Now

#11

Post by yetihehe »

unsupp0rted wrote: post #6

Could an object like 3I theoretically tell when eyes are being pointed at it? Probably not ground-based eyes, but possibly Hubble. i.e. "the inhabitants are scanning us"

If it had several kilometer wide imaging array, then yes. Hubble and other telescopes are totally passive optics. You need to see the distant dot and have enough resolution to identify it as a telescope and see that it is pointing at you. Seeing hubble from more than 1 au would require optics about 8km in size. This doesn't need to be one giant mirror, could be two cameras 8km apart, but synchronized optically (distance known to a small part of wavelength of light). Seeing Hubble as more than 1 pixel to tell that it's a telescope pointing at you needs something much larger.

Re: Interstellar Comet 3I/Atlas: What We Know Now

#13

Post by jandrewrogers »

drewg123 wrote: post #3

> The Rubin observations also show hints of a dusty tail, but oddly this elongation points directly toward the Sun. Typically, the push of the Sun’s radiation moves dust in comet’s tails so that it points away from the Sun. Deceleration burn?

While uncommon, some ordinary comets also have an "anti-tail" that points toward the sun. As a recent famous example, the very bright comet in October 2024 [0] had a prominent anti-tail. The main photo on the wikipedia page shows it clearly.

[0] https://en.wikipedia.org/wiki/C/2023_A3_(Tsuchinshan–ATLAS)

Re: Interstellar Comet 3I/Atlas: What We Know Now

#14

Post by Fripplebubby »

One interesting thing I learned from this was how they determined the probable size of this comet probabilistically, rather than using direct observation - basically, based on the observations, it could either be really big (10km) or really small (0.5km), and we can basically rule out really big because we've been looking for comets for years, and during that time, to see one that is that big implies that we _should have seen_ thousands that are quite small over that time period, because the size of space objects follows a power law since they're always whacking into each other and breaking up. Since we've only seen one small interstellar object during that time rather than thousands, a large comet is so impossibly unlikely that we can conclude that it is 0.5km in size. I'm sure at some point this will be confirmed in a more conventional way, as well.

Re: Interstellar Comet 3I/Atlas: What We Know Now

#15

Post by mathgeek »

unsupp0rted wrote: post #6

Could an object like 3I theoretically tell when eyes are being pointed at it? Probably not ground-based eyes, but possibly Hubble. i.e. "the inhabitants are scanning us"

Theoretically, any sentient being with the necessary technology to get a craft to our solar system and spot the aiming of a telescope at that distance would have even better technologies for detecting what we are doing.

Re: Interstellar Comet 3I/Atlas: What We Know Now

#16

Post by ge96 »

drewg123 wrote: post #3

> The Rubin observations also show hints of a dusty tail, but oddly this elongation points directly toward the Sun. Typically, the push of the Sun’s radiation moves dust in comet’s tails so that it points away from the Sun. Deceleration burn?

We might be the blue people

Re: Interstellar Comet 3I/Atlas: What We Know Now

#19

Post by bmiekre »

EspadaV9 wrote: post #18

With the number of interstellar objects being detected only going up, it would be amazing if we could get some probes to hitch a ride on them. Imagine something lasting as long as Voyager 1 but travelling 3.5x the speed as it leaves the solar system.

I would guess there all kinds of technical logistics reasons as to why this is improbable, but I agree that would be really cool.

Re: Interstellar Comet 3I/Atlas: What We Know Now

#20

Post by kqgnkqgn »

EspadaV9 wrote: post #18

With the number of interstellar objects being detected only going up, it would be amazing if we could get some probes to hitch a ride on them. Imagine something lasting as long as Voyager 1 but travelling 3.5x the speed as it leaves the solar system.

Visiting one with a probe would surely be amazing in it's own right...but hitching a ride would mean matching velocities with them. And if you can do that...you're already in the same orbit, so the comet doesn't really help.
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