Images reveal exocomets around nearby stars
22 comments
·January 31, 2025hinkley
Someone once broke my brain about hostile alien movies. They said if the aliens were here to take, they could stay in the Oort Cloud or outer planets where the gravity well is shallow, and strip mine our system for natural resources and we wouldn’t even be able to throw anything that high to stop them.
We could just watch and shake our fists as they steal our future at their leisure. They wouldn’t even have to send their people. They could use robots on ten systems at once.
ianburrell
The first valuable thing on Earth is life. Life may be rare enough, or diverse enough, that worth sampling the unique life on Earth. The intelligent monkeys can be useful, but can be knocked down is cause problems.
The second valuable thing is intelligent life. The intelligent monkeys are worth preserving and talking to. But their advanced civilization has lots of potential dangers so need controlling protectorate.
The third valuable thing is better minerals. The active processes of the Earth concentrates minerals. They could grind up a whole asteroid, but cheaper to take from Earth. Also, biologic processes make minerals; vacuuming up coal is cheaper than making it. These wouldn't be whole civilization but pirates grabbing some cheap loot before the authorities and natives notice.
The fourth valuable thing is Earth itself. Inhabitable planets are rare. The expected way would be apocalypse or annihilation. But I think it would be more interesting to have alien invasion where they ignore us. They settle the arctic, and don't do anything until attacked. Then they start removing CO2 until the temperatures drop and ice age returns.
ceejayoz
> we wouldn’t even be able to throw anything that high to stop them
Worse, they could throw bits of the Oort Cloud at us.
ridgeguy
It takes just as much ∆V to throw a rock from the Oort cloud to Earth as to throw the same rock from Earth to the Oort cloud. The aliens don't get an energy advantage by holding the high ground.
ceejayoz
> It takes just as much ∆V to throw a rock from the Oort cloud to Earth as to throw the same rock from Earth to the Oort cloud.
Yes, but they clearly have the capability to get to the Oort Cloud, and we (other than a small probe) do not. Having the high ground (both physically and technologically) makes holding the Oort Cloud a pretty good spot to be in.
(It also takes substantially less ∆V to nudge an existing rock into a nastier trajectory, and we're essentially a big easy to hit static target.)
lazide
No it doesn’t, at all.
The whole point of the high ground is someone just needs to ‘drop’ something in, which is cheap and easy, but someone on the ‘low ground’ needs to make up all the energy to get up there before they are even at the same level.
The energy involved in de-orbiting something and dropping it to the surface of earth (at very high speed) is orders of magnitude less than it would take to get the same mass to even earth orbit from the surface.
Holding a brick over the opening of a well is a much more credible threat to someone at the bottom, than that someone with the same brick threatening to throw it back out.
perihelions
That's not actually true; it's an asymmetric problem. You're asking about impacting another orbiting object with nonzero relative velocity. That's not the symmetric question of transferring between two orbits A and B, both ways; it's the asymmetric question of going from orbit A to "some orbit that intercepts B at some point".
It's much less delta-v to go from the Oort cloud to Earth—to a highly-eccentric orbit that intercepts the Earth's orbit, without matching its velocity.
hinkley
When you’re standing at the bottom of a well, don’t mouth off to the person standing at the top.
divbzero
I always thought that comets come from the Oort cloud, but apparently short-period comets come from the Kuiper belt or its associated scattered disk—similar to the exocometary belts in these images.
holoduke
I always wonder. If we theoretically could know for each photon the direction vector and distance travelled, then could we make a collector that could image an exoplanet? Or is this simply impossible?
wongarsu
We actually already have multiple images of exoplanets. [1] and [2] were both taken with the Very Large Telescope in Chile. Granted, you can't see much beyond reddish blobs. But they are not that much worse than Hubble's images of Pluto [3].
We probably can't do much better with earth-based telescope arrays due to atmospheric distortions. But with satellite launch costs coming down we will see large telescope arrays in orbit in a couple decades, and those might do a lot better
[1] https://science.nasa.gov/resource/2m1207-b-first-image-of-an...
AtlasBarfed
Doesn't that practically guarantee Exoplanets in those systems?
tantalor
The article says we already knew that:
> astronomers knew disks of debris leftover from planet formation were common around newborn stars
The new result allows much more insight:
> only a few have been resolved in sufficient detail to study their internal structure. “This is the first time we can make a statistical analysis of what’s going on in these disks,
It's a neat result, its maybe a bit to specify sizes. At least with the images provided in the article, they're getting maybe:
10 pixels, across across objects of >1 astronomic unit (149,597,870 km). If those rings are like our own Kuiper belt objects, then those are more like 25-50 AU. If they're like the asteroid belt in the inner solar system, then maybe 2-5 AU.
If those are images from the nearest 74 solar systems, then those are somewhere from 4 ly to 20 ly away (~4e13 km to 2e14 km away). [1][2] They're probably further away.
Based on the stated resolution, ALMA is supposed to get ~10 milliarcseconds (10−7 radians) resolution. [3] With the small angle approx. that means it can resolve:
It's cool though, as it at least implies disc path clearing, orbital harmonics resulting in ring formation, and probably a lot of other implications. Likely gives excellent regions to try looking for further planets, planetoids, or planetesimals. Provides some idea of how likely it is for the conditions in our own solar system to cause similar formations in further away solar systems. Mostly a lot of single rings, not that many double ring groups. Quite a few that end up looking more like bloby clouds.[1] 100 Nearest Star Systems, http://www.recons.org/TOP100.posted.htm
[2] GJ 1005 (#74), https://en.wikipedia.org/wiki/GJ_1005
[3] Atacama Large Millimeter Array, https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array