4 ms·

Images reveal exocomets around nearby stars

101 points by gmays 2y ago

AtlasBarfed 2y ago
Doesn't that practically guarantee Exoplanets in those systems?
- tantalor 2y ago
  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,
divbzero 2y ago
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.
araes 2y ago
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: (~4e13 km to 2e14 km) * 10^-7 = 4e6 km to 2e7 km = 0.025 AU to 0.125 AU 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 http://www.recons.org/TOP100.posted.htm [2] GJ 1005 (#74), https://en.wikipedia.org/wiki/GJ_1005 https://en.wikipedia.org/wiki/GJ_1005 [3] Atacama Large Millimeter Array, https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array
hinkley 2y ago
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.
- ceejayoz 2y ago
  > 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.
  - hinkley 2y ago
    When you’re standing at the bottom of a well, don’t mouth off to the person standing at the top.
  - ridgeguy 2y ago
    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 2y ago
      > 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 2y ago
      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.
holoduke 2y ago
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 2y ago
  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-exoplanet/ https://science.nasa.gov/resource/2m1207-b-first-image-of-an... [2] https://www.eso.org/public/images/eso2011b/ https://www.eso.org/public/images/eso2011b/ [3] https://esahubble.org/images/opo1006h/ https://esahubble.org/images/opo1006h/

101 points by gmays 2y ago

AtlasBarfed 2y ago

Doesn't that practically guarantee Exoplanets in those systems?

tantalor 2y ago
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,

divbzero 2y ago

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.

araes 2y ago

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: (~4e13 km to 2e14 km) * 10^-7 = 4e6 km to 2e7 km = 0.025 AU to 0.125 AU 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 http://www.recons.org/TOP100.posted.htm [2] GJ 1005 (#74), https://en.wikipedia.org/wiki/GJ_1005 https://en.wikipedia.org/wiki/GJ_1005 [3] Atacama Large Millimeter Array, https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array

hinkley 2y ago

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.

ceejayoz 2y ago
> 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.
- hinkley 2y ago
  When you’re standing at the bottom of a well, don’t mouth off to the person standing at the top.
- ridgeguy 2y ago
  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 2y ago
    > 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 2y ago
    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.

holoduke 2y ago

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 2y ago
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-exoplanet/ https://science.nasa.gov/resource/2m1207-b-first-image-of-an... [2] https://www.eso.org/public/images/eso2011b/ https://www.eso.org/public/images/eso2011b/ [3] https://esahubble.org/images/opo1006h/ https://esahubble.org/images/opo1006h/