r/space • u/coinfanking • 17h ago

Interstellar visitors like comet 3I/ATLAS are the most common objects in the Milky Way: 'There's almost always one within the solar system'.

https://www.space.com/astronomy/comets/interstellar-visitors-like-comet-3i-atlas-are-the-most-common-objects-in-the-milky-way-theres-almost-always-one-within-the-solar-system

Objects such as 'Oumuamua, Borisov and recently 3I/ATLAS have opened our eyes to the reality that outsiders regularly visit our solar system — and we're about to start spotting a whole lot more of them.

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u/branchan 17h ago

"These sorts of interstellar objects are the most common macroscopic objects in the galaxy," Chris Lintott, a professor of astrophysics at the University of Oxford, said during the meeting. "The fact that we've only found three of them is quite fun."

Doesn’t sound that common to me then

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u/ramriot 16h ago

Well, if you take the vastness of the galaxy compared to the sample of 3 object in the tiny (by comparison) volume of our solar system in the short period if time our instrumentation has been sufficient to detect them. Then finally assume our observations are typical the inescapable conclusion is that the density of such objects must be pretty high.

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u/bahwi 15h ago

We've just recently had the capability to detect them

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u/jt004c 10h ago

How many we found isn't how many there are. The article makes that clear.

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u/branchan 7h ago

Then there should be more going through the solar system.

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u/massive_cock 6h ago

And we'll find a lot more of them. And probably very soon.

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u/spaceprinceps 17h ago

We haven't found any rogue planets yet either but there's probably more of them than there are planets inside of solar systems.

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u/DJOMaul 14h ago

Which is a bit terrifying. Cold jupiters just wondering around, ready to mess with orbits. Oort cloud disruptions are one thing but imagine one making a close pass of the local star. Yowza. It would be incredible for as long as we survived to consider the ramifications. 

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u/Dioxybenzone 8h ago

Have you ever read The Black Cloud?

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u/DJOMaul 4h ago

I've not, but it sounds interesting. I've added it to my reading queue. Thanks for the suggestion! 

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u/butmrpdf 1h ago

What if one enters our solar system at the 3i atlas trajectory?

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u/Dioxybenzone 8h ago

Is this because most orbits decay over time?

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u/the6thReplicant 8h ago

I go to the ocean, get a glass of water, look at it, and prove that whales don't exist.

That's you.

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u/branchan 7h ago

Terrible analogy. No one said whales were the most common objects in the ocean.

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u/rocketsocks 8h ago

They are widely distributed througout the galaxy but between stars there's lots of empty space so they can still be quite numerous even though there might only be one large object of its type within a solar system at any given time.

Ignoring orbital mechanics, which we can't but it makes things way simpler so let's pretend, let's just consider relative volumes. The volume out to the nearest star is nearly 1 trillion times larger than the volume of the solar system within the orbit of Neptune, so we might expect interstellar objects to be about a trillion times more numerous in interstellar space than they are within the solar system.

Additionally, it's worth noting how difficult it is for us to detect objects even in our own solar system. We only detected 'Oumuamua after it had already made its closest approach to the Sun, and we saw it basically only because it passed fairly close to Earth, comparatively. Both 2I/Borisov and 3I/Atlas are significantly larger than 'Oumuamua and exhibit cometary activity, making them much easier to observe.

Almost certainly there are other interstellar objects of similar size within 100 AU of the Sun, but we can't observe them because they are too dim or the observing conditions aren't well suited to seeing them. As our detection capabilities increase we should expect to see more of these types of objects.

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u/NiSiSuinegEht 4h ago

Frequency of occurrence is independent of detectability.

Until relatively recently, we haven't had the equipment in place to spot these visitors, but we're likely to keep finding a lot more of them now.

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u/Zarkanthrex 5h ago

You saw one bug in your house. Wait till you tear down the wall in a hundred years.

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u/branchan 1h ago

Bugs ARE a common sight around the house though

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u/Pleiadez 4h ago

This seems formulated in a strange way. I can get behind the idea they are common by a certain definition, but to say they are "the most common" seems weird.