[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 : 113 points
Date : 2024-11-23 15:51 UTC (1 days 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. :)
| Keysh wrote:
| Tardigrades are not "extremophiles", which refers to
| organisms that _live_ (grow, reproduce) in "extreme"
| environments ("phile" = "like, love"). Tardigrades can
| temporarily survive some rather extreme conditions, but
| they generally require fairly ordinary environments to
| actually live. (As suggested by common names like "water
| bear" and "moss piglet".)
| dekhn wrote:
| Deep-earth chemoautotrophs might survive that. But
| ultimately, if the deep subsurface exceeds 150C, it would
| be hard to survive.
| fecal_henge wrote:
| Intollerable stuffyness.
| southernplaces7 wrote:
| I think you should read the text a bit more closely. A
| 700km impactor would be required to completely boil the
| oceans into vapor, but the article mentions that a much
| more insanely huge impactor of between 2000 and 2,700km
| would be needed to genuinely sterilize the earth because
| it entirely melts the crust.
|
| However, (and here I speak from reading many other
| sources on this subject), even something the size of that
| latter object (basically something the size of a planet
| like Pluto) might not be enough.
|
| Other studies have indicated that it might be
| exceptionally hard for heat to transfer enough through
| the vast mass of the earth's upper mantle and crust to
| actually melt it uniformly even if hit by something like
| the object that may have formed the moon.
|
| This impactor was also supposed to be roughly 2,500km
| across and some of the theoretical concepts around it
| argue that even in that absolutely cataclysmic scenario,
| at least a part of the crust remains intact and
| relatively cool below a depth of several hundred meters.
|
| If such a thing were to be true in the context of modern
| earth, which teems with life in every single possible
| remotely habitable nook and cranny and crevasse, then
| even a colossal impact by a 2,700km planet-type object
| wouldn't sterilize the Earth of life.
|
| If only part of the crust remained intact as described
| above, then after hundreds of thousands or a few million
| years, as the earth's partially molten surface cools, and
| an atmosphere reforms, water that also reforms from vapor
| would rain down to the surface again in a vast global
| storm like something out of the bible. As this happens
| and the oceans refill, the tiny organisms concealed
| during all that time inside the deep cracks hundreds of
| meters below the surface of that surviving part of our
| world's crust would then recolonize the surface
| eventually and cause life to flourish again.
|
| The key things in this scenario are that for one, at
| least one small part of the crust remains intact and
| cool, at least below a certain depth, and secondly, that
| water vapor eventually re-condenses into rain.
|
| One might think that water would be vaporized right into
| separation of its hydrogen and oxygen atoms by the heat
| of such impacts, but mostly no. For that to happen the
| water on Earth would need to be subjected to at least
| something like 3,000 degrees Celsius of sustained heat,
| and even a planet-sized impact wouldn't generate such
| temperatures over most of the world.
| pfdietz wrote:
| I wrote "> 700 km". I did that deliberately, and was not
| asserting that 700 km was enough.
| thangalin wrote:
| "The layer was deposited when an asteroid between 11 and 15
| kilometres in diameter impacted Earth."
|
| https://impacts.to/downloads/lowres/impacts.pdf#page=21
|
| Sources: https://impacts.to/bibliography.pdf (search for
| K-Pg)
| 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...
| sebastiennight wrote:
| OK I'm curious about this bit. How do you deduce the range
| of height of the ejecta from a calculation of the kinetic
| energy of the impactor?
| 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
| cozzyd wrote:
| Nary a username more apt.
| pfdietz wrote:
| I don't think anything beyond the elemental composition of
| the impactor would matter much since the impact would heat
| it to a temperature at which it would be in chemical
| thermodynamic equilibrium, regardless of what its initial
| molecular composition was.
| 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), increase cadence, increase mission scope,
| and cut flight times, by cutting NASA's build-&-burn rocket
| manned program in favor of SpaceX's reusable manned craft
| and space refueling 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 (a) fewer
| risky/complex unfolding maneuvers in flight, (b) much
| easier radiation mitigation via more shielding, larger more
| resilient circuits, redundancy, etc. And (c) fewer craft,
| with more capabilities and higher longevity.
|
| And as with the manned program, increase mission scope,
| while reducing transfer to target times, via in orbit
| refueling.
|
| If only we could find someone with the incentives, plan,
| means and mandate, to cut government space spending while
| somehow also expanding its manned & scientific space
| exploration capabilities and scope.
|
| The hardest part is to find such a uniquely capable person,
| who also has enough slack time to take this on. A rare
| trait combination, indeed. What are the chances of finding
| a genius reefer doom scrolling bloviating slacker? Who
| could put all that disposable time to better use?
| Nevermark wrote:
| In case that all seemed too pro-SpaceX:
|
| 1) I think NASA does best when it focuses on the frontier
| of space, where private industry does not yet have the
| incentives or capabilities to increase our knowledge and
| access to space and solar system resources.
|
| 2) I think NASA does best, when it takes the greatest
| advantage of private industry, where ever industry is
| able to provide lower costs or higher performance.
|
| I think this is more in line with how public money should
| be spent.
|
| I think it reduces a lot of wasted money spent on
| unnecessary redundant and obsolete efforts.
|
| I think it results in the greatest bang for the buck, for
| the government, and the greatest incentive to improve for
| industry.
|
| At this time, I think the frontier NASA should be focused
| on (where industry is not yet incentivized enough), is
| manned space habitats, and unmanned and manned
| exploration of the solar system's potential manned sites
| and resources.
|
| Where I think it should have already passed on the torch,
| is manned and unmanned orbital, lunar and solar system
| launch capabilities. Industry is already performing and
| incentivized to provide these capabilities better than
| NASA. NASA can best contribute to improving those
| capabilities, with the least investment, by being a
| demanding customer.
|
| SpaceX happens to have put itself in the center of those
| principles, due to a lot of fine work. But the principles
| make just as good sense, regardless of who the industrial
| innovators are.
| deprecative wrote:
| If we actually funded public services to the required
| levels NASA and so forth would be fine to do things in
| house. We're just allergic to anything that makes actual
| sense when we have an oligarchy to support. That's it.
| chgs wrote:
| NASA hasn't run its own rockets for a long time, it is a
| customer, it chooses the launch vehicle based on the
| mission requirements.
| gnarlouse wrote:
| Department of Gaia Escape
| Dalewyn wrote:
| Department of Galactic Exploration
| gnarlouse wrote:
| Department of Glorious Evolution
| yencabulator wrote:
| X.gov
| Dalewyn wrote:
| NASA and most of the unmanned space exploration programs will
| probably be fine.
|
| It's the manned space exploration programs and all the space-
| as-in-vapid programs that could and should be cut with
| extreme prejudice.
|
| And in case I need to make myself clear: There is no value in
| manned space exploration at this point, at least no value
| that can't be obtained with unmanned programs. I say that as
| someone who was and will always be fascinated by Apollo,
| Space Shuttle, et al.
| vlovich123 wrote:
| > It's the manned space exploration programs and all the
| space-as-in-vapid programs that could and should be cut
| with extreme prejudice.
|
| The main thing on the chopping block is all rocket R&D and
| forcing NASA to contract out that work. It's unlikely Musk
| would suggest chopping the programs themselves as those are
| very lucrative contracts SpaceX would be bidding for.
|
| > no value in manned space exploration at this point
|
| Only if you ignore the value of inspiring the next
| generation of scientists and explorers.
| Dalewyn wrote:
| >the chopping block is all rocket R&D and forcing NASA to
| contract out that work.
|
| Nearly everything NASA does outside of operating the
| missions themselves is contracted out, especially the SLS
| which is _all_ of it:
|
| * The main stage (aka core stage), essentially a
| repurposed Space Shuttle external fuel tank with engines
| bolted on, is contracted out to Boeing, with so far _one_
| launch and _two_ completed production units in _at least
| ten years_ of production.
|
| * The main engines, which are refurbished SSMEs used as
| throwaways, are contracted out to Aerojet Rocketdyne.
|
| * The SRBs are contracted out to Northrop Grumman, and
| the first eight launches will all be reusing the old
| Space Shuttle SRBs.
|
| * The second stage, a repurposed Delta IV second stage,
| is contracted out to United Launch Alliance which is
| basically Boeing and Lockheed Martin.
|
| * Finally, the Orion is contracted out to Lockheed Martin
| and Airbus. Incidentally, this is the only "new"
| component of the program.
|
| https://en.wikipedia.org/wiki/Space_Launch_System
|
| https://en.wikipedia.org/wiki/Orion_(spacecraft)
|
| >Only if you ignore the value of inspiring the next
| generation of scientists and explorers.
|
| Unmanned programs like Hubble and the other Great
| Observatories, New Horizons,
| Spirit/Opportunity/Curiosity, and the two Voyagers
| inspire the people far more than manned programs.
|
| There _was_ value in manned programs before, we needed to
| figure out WTF human bodies will do in space. We figured
| that out at least 20 years ago. Now we need to keep
| contriving excuses to keep ISS flying and there 's barely
| enough commercial interest in manned space utilization.
|
| No, cut it all. Until we reach the next paradigm shift
| where we have to send men out into the black again to
| gain answers, robots can do everything a man could for
| cheaper, safer, longer, and faster.
| vlovich123 wrote:
| > Nearly everything NASA does outside of operating the
| missions themselves is contracted out, especially the SLS
| which is all of it:
|
| Kind of but not quite AFAIK. The design, specification
| building, and various prototyping happens within NASA.
| They contract out once they know what they want to build.
| Musk doesn't have the ability to cancel the SLS. That
| would require an act of Congress and face all the same
| obstacles as why the SLS got created in the first place
| (to save jobs that would have been cut after the
| cancellation of the shuttle). However, he would be able
| to cut the design and specification building &
| prototyping that NASA does and instead force them to
| contract out for that (preferably to SpaceX).
|
| The entire focus of DOGE seems to be to reduce the number
| of employees, not to cut programs. The reason for that is
| also tactical sabotage. It's hard to cut programs because
| politics gets involved. But if you could mass fire
| employees so that government can't succeed at those
| programs, then you can follow up later and point to how
| government is incompetent and the programs need to be cut
| since they're not meeting their goals.
|
| > Unmanned programs like Hubble and the other Great
| Observatories, New Horizons,
| Spirit/Opportunity/Curiosity, and the two Voyagers
| inspire the people far more than manned programs.
|
| Unmanned programs inspire people already inclined to
| science & exploration of the unknown. They do not inspire
| people who aren't so inclined and who instead look
| towards heros to show them what's possible or ask "why
| are we spending any money on space exploration". Said
| another way, unmanned programs don't inspire people to
| become astronauts or value spending on research into
| exploration. Neil Armstrong landing on the moon inspired
| a lot of people to dream of becoming astronauts and
| perhaps spark their interest in science in the first
| place.
|
| That's why the Mars program is important even if
| scientifically it's of limited value.
|
| One thing I'll highlight. While Musk is a darling for
| SpaceX today because SpaceX is competing aggressively,
| over time SpaceX will inevitably morph into the next
| Boeing and put us back into the same problems if they're
| allowed to monopolize the government funds.
| Polizeiposaune wrote:
| Would be very challenging to get there in time.
|
| 11AU is outside Saturn's orbit. With the high inclination of
| the orbit (95 degrees) it's coming in on a more-or-less polar
| orbit of the sun. You might need a Jupiter flyby along the
| lines of what Ulysses did to fling it out of the ecliptic
| plane, but Jupiter might not be in the right place in its orbit
| to make that work..
|
| And you'd need a very light spacecraft (not much mass budget
| for instruments) launched very fast, and it's far enough away
| from the sun that you'd want RTG power rather than solar
| panels.
| TheSpiceIsLife wrote:
| I'm far enough away from the sun that I want an RTG rather
| than solar.
| Archelaos wrote:
| > With the high inclination of the orbit (95 degrees) ...
|
| How can such a high inclination be explained?
| Polizeiposaune wrote:
| The observed distribution of inclinations of long-period
| comets are why it's called the Oort cloud and not the Oort
| belt..
|
| Short period comets are relatively close to the ecliptic,
| while very-long-period comets have evenly distributed
| inclinations suggesting that the objects in the Oort are
| more or less spherically distributed.
|
| Discussed here: https://en.wikipedia.org/wiki/Oort_cloud#De
| velopment_of_theo...
| JoeDaDude wrote:
| I can't make a fair comparison between the object in TFA and
| Oumuamua, the presumed interstellar object that passed
| through our Solar System not long ago. For the latter, a
| "Project Lyra" study [1] posits a combination of Earth and
| Jupiter gravitational assists to catchup with Oumuamua. Could
| a similar approach work for this comet?
|
| [1]. https://i4is.org/project-lyra-a-solar-oberth-
| at-10-solar-rad...
| vivzkestrel wrote:
| what would it take to build and accelerate an object to
| 295000 kms/s? Like seriously, would it take nuclear
| propulsion or is it antimatter engine or solar sail?
| lsllc wrote:
| The speed of light is 299792.458km/s so according to a
| quick Google search it takes 4.28x10^17J to accelerate 1kg
| to 0.98c.
| fecal_henge wrote:
| Thats nearly an entire camenbert.
| slyall wrote:
| Comet Interceptor was designed just for this.
|
| _The Comet Interceptor is a robotic spacecraft mission led by
| the European Space Agency (ESA) planned for launch in 2029. The
| spacecraft will be "parked" at the Sun-Earth L2 point and wait
| for up to three years for a long-period comet to fly by at a
| reachable trajectory and speed._
|
| https://en.wikipedia.org/wiki/Comet_Interceptor
| didgetmaster wrote:
| For comets or other objects whose perihelion is less than 1 au;
| does the chance of collision with Earth increase if the orbit is
| within the elliptical plane vs outside it?
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