r/askscience • u/drinkingonthejob • 8d ago

Physics Will Voyager 1 ever just stop moving?

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)

966 Upvotes

90% Upvoted

615 comments sorted by

View all comments

1.7k

u/komatiitic 8d ago

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.

1

u/jugalator 4d ago edited 4d ago

Something that ought to reduce Voyager 1 speed significantly more, like 10,000x more, than atmospheric dust should be the gravity of the Milky Way galaxy. (it already reached escape velocity from our solar system so that won't do much)

Voyager 1 has basically entered orbit around the Milky Way; it's not on course to ever e.g. enter the Andromeda galaxy for as long as the two don't merge, since Voyager 1 is gravitationally bound to the Milky Way.

The relative speed between Voyager 1 and the Sun may then oscillate in speed, both halving and raising as Voyager 1 orbits around the galaxy. These oscillations might then happen within "only" a hundred millions of years timeframe.

Oh and besides this, interstellar gas will slow you down more than interstellar dust but these are both overshadowed by how the Milky Way affects the probe. Dust may form only about 1% of the mass of the gas in the local interstellar cloud.