5 ms·

If you take a random trajectory through our solar system, your chance to pass this close to three planets is < 0.005%.

datadrivenangel 1y ago
Specifically a random angle. "The likelihood for such a perfect alignment of the orbital angular momentum vector around the Sun for Earth and 3I/ATLAS is π(5◦/57◦)2/(4π) = 2×10−3." Sloppy sloppy work.
- pbmonster 1y ago
  I also misread that. The 0.005% is in relation to this: > In the following analysis we assume that 3I/ATLAS is on its current orbit but vary the time-of-entry into the Solar System (or equivalently the time of perihelion), assuming 3I/ATLAS could have come at any time into the Solar System, and happened to do so such that it came within the observed closest approaches of Venus, Mars and Jupiter. The probability of this is 0.005 So exact same trajectory, but analyzed over a long period of time. If it came any earlier or later, it would almost never get this close to exactly those three planets.
  - TheOtherHobbes 1y ago
    The aliens are going to be so annoyed when they realise they missed the interesting one.
    - MarkusQ 1y ago
      No matter how tempting the straight line, I will not make the joke.
      - sebastiennight 1y ago
        You've written too much or too little. The Internet demands to hear it.
        MarkusQ 1y ago
        Oh come on, there are only 8.5±0.5-3, so 5 or 6 possibilities. Go through the list, Mercury through Pluto, mentally saying "I find ____ interesting" and notice which one gives you an eye roll/chuckle/groan.
        sebastiennight 1y ago
        After 2 years of the All-in podcast, I can't believe I still fell for it.
taneq 1y ago
How many objects go through our solar state each year? More than 200? Are their trajectories uniformly distributed?
- pbmonster 1y ago
  We don't know! We only got the telescopes to look for them with any chance of success in 2017. Since then, we saw three. Since they are often small and dark, it's very possible we missed a few.
  - grues-dinner 1y ago
    ATLAS was expanded in 2022, and this object was discovered by the new telescope in Chile - the more we look the more we find. With more survey telescopes coming online (Vera Rubin just recently, Nancy Grace Roman and Xuntian coming soon to name a few), I suspect we'll start seeing quite a few more of these. Hopefully we humans get a mission ready to go that will allow to go and have a look when a suitable one turns up with enough notice. Presumably one that isn't nailing though quite so fast as 3I/ATLAS (ʻOumuamua and Borisov were about half the speed each - about 30km/s). Annoyingly the speeds mean that really all you can do is a very fast flyby, unless you are incredibly lucky with trajectories, the object moves very slowly or we can ship a truly massive amount of "rapid" (e.g. not ion engines if you want to catch it this side of the heliopause) delta-v to orbit. The rocket equation is really not on our side here if we wanted use chemical means. If you have a specific impulse of 300 seconds, you basically cannot get a 100kg probe to 30km/s delta-v without a slingshot. 100 tonnes of fuel gets you to about 20km/s, 2000 tonnes gets you to 30km/s. And a craft that holds 2000 tonnes of fuel probably masses more than 100kg. Maybe the better bet is a really good sunshield and then everyone works on their cardiac health so they can see the intercept in 30 year's time, and even then it's a blink-and-you-miss-it flyby at over 20km/s: http://orbitsimulator.com/BA/lyra.gif http://orbitsimulator.com/BA/lyra.gif
    - pbmonster 1y ago
      > The rocket equation is really not on our side here if we wanted use chemical means. If you have a specific impulse of 300 seconds, you basically cannot get a 100kg probe to 30km/s delta-v without a slingshot Or, hear me out, we built an orbital rail gun.
voidUpdate 1y ago
isnt the chance only for those specific three planets, not any three planets? there are 56 ways to choose three planets from the 8 (sorry pluto) in our solar system, so the probability of passing that close to any three planets is 56x greater

Specifically a random angle. "The likelihood for such a perfect alignment of the orbital angular momentum vector around the Sun for Earth and 3I/ATLAS is π(5◦/57◦)2/(4π) = 2×10−3." Sloppy sloppy work.

pbmonster 1y ago
I also misread that. The 0.005% is in relation to this: > In the following analysis we assume that 3I/ATLAS is on its current orbit but vary the time-of-entry into the Solar System (or equivalently the time of perihelion), assuming 3I/ATLAS could have come at any time into the Solar System, and happened to do so such that it came within the observed closest approaches of Venus, Mars and Jupiter. The probability of this is 0.005 So exact same trajectory, but analyzed over a long period of time. If it came any earlier or later, it would almost never get this close to exactly those three planets.
- TheOtherHobbes 1y ago
  The aliens are going to be so annoyed when they realise they missed the interesting one.
  - MarkusQ 1y ago
    No matter how tempting the straight line, I will not make the joke.
    - sebastiennight 1y ago
      You've written too much or too little. The Internet demands to hear it.
      - MarkusQ 1y ago
        Oh come on, there are only 8.5±0.5-3, so 5 or 6 possibilities. Go through the list, Mercury through Pluto, mentally saying "I find ____ interesting" and notice which one gives you an eye roll/chuckle/groan.
        sebastiennight 1y ago
        After 2 years of the All-in podcast, I can't believe I still fell for it.

taneq 1y ago

How many objects go through our solar state each year? More than 200? Are their trajectories uniformly distributed?

pbmonster 1y ago
We don't know! We only got the telescopes to look for them with any chance of success in 2017. Since then, we saw three. Since they are often small and dark, it's very possible we missed a few.
- grues-dinner 1y ago
  ATLAS was expanded in 2022, and this object was discovered by the new telescope in Chile - the more we look the more we find. With more survey telescopes coming online (Vera Rubin just recently, Nancy Grace Roman and Xuntian coming soon to name a few), I suspect we'll start seeing quite a few more of these. Hopefully we humans get a mission ready to go that will allow to go and have a look when a suitable one turns up with enough notice. Presumably one that isn't nailing though quite so fast as 3I/ATLAS (ʻOumuamua and Borisov were about half the speed each - about 30km/s). Annoyingly the speeds mean that really all you can do is a very fast flyby, unless you are incredibly lucky with trajectories, the object moves very slowly or we can ship a truly massive amount of "rapid" (e.g. not ion engines if you want to catch it this side of the heliopause) delta-v to orbit. The rocket equation is really not on our side here if we wanted use chemical means. If you have a specific impulse of 300 seconds, you basically cannot get a 100kg probe to 30km/s delta-v without a slingshot. 100 tonnes of fuel gets you to about 20km/s, 2000 tonnes gets you to 30km/s. And a craft that holds 2000 tonnes of fuel probably masses more than 100kg. Maybe the better bet is a really good sunshield and then everyone works on their cardiac health so they can see the intercept in 30 year's time, and even then it's a blink-and-you-miss-it flyby at over 20km/s: http://orbitsimulator.com/BA/lyra.gif http://orbitsimulator.com/BA/lyra.gif
  - pbmonster 1y ago
    > The rocket equation is really not on our side here if we wanted use chemical means. If you have a specific impulse of 300 seconds, you basically cannot get a 100kg probe to 30km/s delta-v without a slingshot Or, hear me out, we built an orbital rail gun.

voidUpdate 1y ago

isnt the chance only for those specific three planets, not any three planets? there are 56 ways to choose three planets from the 8 (sorry pluto) in our solar system, so the probability of passing that close to any three planets is 56x greater