[HN Gopher] Size and albedo of the largest detected Oort-cloud o...
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Size and albedo of the largest detected Oort-cloud object
Author : belter
Score : 62 points
Date : 2024-11-23 15:51 UTC (7 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| pmichaud wrote:
| About 137km diameter, so really big, but albedo (surface
| brightness, basically) still similar to other comets.
| pfdietz wrote:
| This object is thankfully not coming anywhere close to Earth,
| but an impact of an object this size with Earth would still not
| sterilize the biosphere, or even evaporate the oceans.
| BobbyJo wrote:
| "Puny rock couldn't even cook every last bacterium on our
| planets surface. Pathetic." - You
| LeifCarrotson wrote:
| The KT impactor has been estimated to have been about 10 km
| in diameter and moving at 20 km/s.
|
| A long-period comet, like an Oort cloud object, might impact
| at 50 km/s, instead of the 10-20 km/s of a near-Earth
| asteroid.
|
| The physics might say that the energy might not be enough to
| literally vaporize the oceans or "sterilize" the biosphere,
| but the global ecosystem is fragile. This thing dropping on
| the planet would absolutely cause a mass extinction.
| pfdietz wrote:
| Oh, I didn't say the results wouldn't be utterly
| catastrophic. It's more a comment on just how surprisingly
| large an impact would be needed for sterilization.
|
| https://iopscience.iop.org/article/10.3847/psj/ac66e8
|
| (extrapolated > 700 km impactor needed for sterilization)
| jajko wrote:
| I don't think anymore absolutely 100% sterilization of
| all life on Earth is possible, we always end up talking
| about 99.999999% or similar. With exception of maybe
| super/hypernova of our Sun which ain't possible, or black
| hole passing directly through/very close to Earth,
| tearing apart every single atom making up this planet
| including all of us on quark level.
| s1artibartfast wrote:
| Colision with a planet or moon would do it, anything that
| turns the surface to lava really.
| sebzim4500 wrote:
| Even then there's a chance a few tardigrades hibernate on
| some material that shoots up and then comes back a few
| years later once the earth has cooled a bit.
| pfdietz wrote:
| I think they could be cooked by thermal radiation as the
| ejecta expands.
| sebzim4500 wrote:
| Probably most would be, but there are a lot of
| microorganisms and only a few need to get lucky.
| blooalien wrote:
| Tardigrades were placed in the "extremophile" class with
| good reason. If _anything_ could survive a truly
| catastrophic impact event, I 'd say the smart money goes
| on the lowly "water bear" to win. :)
| dekhn wrote:
| Deep-earth chemoautotrophs might survive that. But
| ultimately, if the deep subsurface exceeds 150C, it would
| be hard to survive.
| belter wrote:
| My quick back of envelope calculations...
|
| Imply that the kinetic energy released upon the impact of
| such an object, show a group sheltering at the ISS (orbit at
| an altitude of between 370-460 km (200-250 nmi)) or the
| Tiangong (orbit between 340 and 450 km (210 and 280 mi) )
| would not be likely to survive the impact from ejecta thrown
| into their orbital altitude...
| perihelions wrote:
| It'd certainly sterilize the vertebrate part of the
| biosphere: a significant part of its chemical composition
| (per the paper) should theoretically be CO and HCN.
| "Hypervolatiles" is the term the paper uses--primordial evils
| that can only exist in the coldest outer reaches of the Oort
| cloud, far away from the star that evaporates them.
|
| I don't know the exact numbers, but for water ice the "frost
| line" is at about 3 au (between Mars and Jupiter)[0]--the
| line inside which icy comets and ice moons, like Europa,
| can't form. Presumably there's analogous zones for the
| increasingly volatile cryogenic ices, going out into the most
| distant regions--a solid carbon dioxide line, a carbon
| monoxide line, a cyanide line... The surface of Pluto, for
| example, is mostly solid nitrogen, with parts of solid
| methane and solid carbon monoxide [1].
|
| [0] https://en.wikipedia.org/wiki/Frost_line_(astrophysics)
|
| [1] https://en.wikipedia.org/wiki/Pluto#Geology
| hinkley wrote:
| If it's made of the same stuff as comets, there would be some
| value to blowing it up, since more parts would then evaporate
| before impact. Right?
| Simon_ORourke wrote:
| 11AU is close enough thank you very much
| atemerev wrote:
| Hey, I want another Hale-Bopp, which was at 0.9 AU.
| webdoodle wrote:
| Is this the '9th planet' that Batygin and Brown, inferred the
| existence of based off the orbital tracks of smaller objects in
| the Oort cloud?
|
| https://astrobiology.nasa.gov/news/caltech-researchers-find-...
| perihelions wrote:
| No; it's about 30 million times too small. :)
| Tuna-Fish wrote:
| No, this is way too small and close for that.
| d_silin wrote:
| I wonder if we can get a flyby mission by 2031 from NASA or ESA.
| AlphaEsponjosus wrote:
| I wonder if NASA will still existing in 2028.
| chgs wrote:
| NasaX, or maybe NAXA or something.
| Nevermark wrote:
| Well XASA obviously!
|
| The government would save billions (tens of billions over
| the long haul), and increase cadence, by cutting NASA's
| build-&-burn rocket manned program in favor of SpaceX's
| reusable manned craft services.
|
| SpaceX Starship could also reduce the cost and increase
| cadence of scientific missions, in two ways:
|
| 1) By reducing launch costs via greater system reuse.
|
| 2) And by increasing available launch volume, eliminate a
| lot of the design & manufacturing time, cost, complexity
| and risk created by today's need to fit craft into toad's
| more limited volumes.
|
| Less need for craft miniaturization means (1) fewer
| risky/complex unfolding maneuvers in flight, (2) much
| easier radiation mitigation via more shielding, larger more
| resilient circuits, redundancy, etc. And (3) fewer craft,
| with more capabilities and higher longevity.
|
| If only we could find someone with the incentives, plan,
| means and mandate, to cut government space spending while
| somehow also expanding its space exploration.
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