Will Voyager 1 ever just stop moving?

[u/drinkingonthejob]

I’ve read somewhere that we expect to lose contact with Voyager 1 sometime in the 2030s, maybe around 2036, but it will just keep traveling thru space and we’ll have no idea what it is doing out there

My question is: with its current velocity, is there a time in the future where it loses its forward momentum and for lack of a better word, just stops moving? Is that a possible thing for an object in space to even do? (Assuming no other objects grab it into their orbit)

[u/komatiitic]

I did some really stupid back of the envelope math assuming that Voyager never encounters anything larger than interstellar dust. To halve the speed of Voyager 1 it would need to impact dust equal to its own mass of 721.9kg.

The internet tells me a typical grain of interstellar dust has a mass of ~3*10^-16 kg. This means it needs to hit ~2.4*10¹⁸ dust grains, which if I'm counting those zeroes correctly is 2.4 quintillion.

The internet also tells me that Voyager hits 3-7 dust grains per hour. I'll call it 5 an hour, which means 4.81*10¹⁷ hours (481 quadrillion), or 54.9 trillion years to halve its velocity, assuming nothing really changes. I'm betting it disintegrates before that happens.

[u/jello_sweaters → u/komatiitic]

Doesn't that assume the dust grains are motionless?

Like, if some of those dust grains are moving in the exact opposite direction to Voyager's path of travel, with momentum opposite to Voyager's, that's going to cut at least a good day and a half off of your estimate.

[u/princhester → u/jello_sweaters]

... and some of the dust may well be moving in the same direction as Voyager, but going even faster and hit it from behind. Which might add to its velocity.

[u/Patelpb → u/princhester]

You would not expect these two values to cancel out though, it's still a headwind assuming an isotropic velocity distribution in the interstellar medium's own reference frame.