dwarf planet inflates by one third, or does it?

h2ouniverse · Dec 5, 2008

Dwarf planet candidate 2005 QU182, previously identified as of 3.7 absolute magnitude, has been upgraded to 3.1 thanks to recent observations. [Minor Planet Center]Absolute magnitude becomes brighter than Varuna (3.6), 2002TC302(3.8), Ixion (3.2), 2002AW197 (3.3). Would be 8th in absolute magnitude behind only Eris, Pluto, Haumea, Makemake, Sedna, Orcus and Quaoar.For a given albedo, that corresponds to an increase by 33% in diameter. Depending on albedo, that could make it wider than 1200km. Most probable size range is 600-800km. That would be enough though to secure dwarfplanethood ultimately when IAU gets evidence of its shape. However:* large TNOs tend to have higher albedos, that would lead to a lesser increase in diameter* changes in surface composition have been observed on Pluto, Eris; could it be that its albedo increases as it goes further from Sun if some components of an atmosphere now freeze (was at perihelion at 37AU in 1970, now at 48AU)?

UFmbutler · Dec 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Dwarf planet candidate 2005 QU182, previously identified as of 3.7 absolute magnitude, has been upgraded to 3.1 thanks to recent observations. [Minor Planet Center]Absolute magnitude becomes brighter than Varuna (3.6), 2002TC302(3.8), Ixion (3.2), 2002AW197 (3.3). Would be 8th in absolute magnitude behind only Eris, Pluto, Haumea, Makemake, Sedna, Orcus and Quaoar.For a given albedo, that corresponds to an increase by 33% in diameter. Depending on albedo, that could make it wider than 1200km. Most probable size range is 600-800km. That would be enough though to secure dwarfplanethood ultimately when IAU gets evidence of its shape. However:* large TNOs tend to have higher albedos, that would lead to a lesser increase in diameter* changes in surface composition have been observed on Pluto, Eris; could it be that its albedo increases as it goes further from Sun if some components of an atmosphere now freeze (was at perihelion at 37AU in 1970, now at 48AU)? Posted by h2ouniverse</DIV>I would be more inclined to believe some composition/phase change of the material on the surface is responsible.  Dwarf planets are most certainly rocky bodies, and I can't think of any reason for a rocky body to suddenly inflate by such a large amount, barring some kind of weird(really weird) seismic activity.  I'd guess some things have frozen, or a large impact threw up a bunch of dust with a higher albedo(although this would most certainly change the orbit, and the change would probably decrease with time, so it could easily be proven wrong by observing it again at the same distance at a later time). <div class="Discussion_UserSignature"> </div>

h2ouniverse · Dec 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I would be more inclined to believe some composition/phase change of the material on the surface is responsible.  Dwarf planets are most certainly rocky bodies, and I can't think of any reason for a rocky body to suddenly inflate by such a large amount, barring some kind of weird(really weird) seismic activity.  I'd guess some things have frozen, or a large impact threw up a bunch of dust with a higher albedo(although this would most certainly change the orbit, and the change would probably decrease with time, so it could easily be proven wrong by observing it again at the same distance at a later time). Posted by UFmbutler</DIV> Actually, dwarf planets are thought to be icy bodies (with rocky material but a lot of volatiles, with densities seldom beyond 2, excepted Haumea for now), akin to the icy moons of the giant planets in bulk composition.Of course when I said "inflates" I meant the 1.3x inflation of the knowledge of the diameter, not a physical change in diameter! "Or does it" expressed doubts that a change in actual albedo or theoretical albedo could mitigate this advancement in the ranking of big TNOs.It is indeed possible that some change occured in the albedo (due to condensation e.g.). But most likely, this is probably just an issue of poor previous assessment. TNO orbits are generally poorly known. So evaluation of distance to Sun can be very unaccurate at the beginning, and that acts on the evaluation of absolute magnitude (got from apparent magnitude by taking onto account the distance to Sun). The dependency is according to the fourth power of the distance so this is quite sensitive...

3488 · Dec 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I would be more inclined to believe some composition/phase change of the material on the surface is responsible.  Dwarf planets are most certainly rocky bodies, and I can't think of any reason for a rocky body to suddenly inflate by such a large amount, barring some kind of weird(really weird) seismic activity.  I'd guess some things have frozen, or a large impact threw up a bunch of dust with a higher albedo(although this would most certainly change the orbit, and the change would probably decrease with time, so it could easily be proven wrong by observing it again at the same distance at a later time). Posted by UFmbutler</DIV>Hi UFmbutler, That would be the logical approach. However no one alive today can do it as the orbital period is 892.5 years. Yes it does seem likely that 2005 QU182 is mostly rocky as are Eris, Pluto & Haumea.Any changes on albedo are almost certainly frosts condensing onto to the surface from a thin 'atmosphere' crashing out onto the surface.There may be cryovolcanism of the sort seen on Enceladus & Triton & suspected now for Eris, Quaoar & Charon (maybe Pluto), rather than high temp volcanism as on Earth & Io. 2005 QU182 is a large body, certainly more than large enough to have cryovolcanism. It's just does 2005 QU182 actually have it? I suspect the increase in albedo is an 'atmosphere' frosting out onto the surface.As 2005 QU182 has passed perihelion during this 892.5 'year', that seems more likely. Andrew Brown.  <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

3488 · Dec 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Actually, dwarf planets are thought to be icy bodies (with rocky material but a lot of volatiles, with densities seldom beyond 2, excepted Haumea for now), akin to the icy moons of the gi..................  Posted by h2ouniverse</DIV>Hi Joel, I thought Pluto & Eris were thought to be approx 75% by mass silicate rock with ice mantles / crusts surrounding said rocky cores (assuming they're differentiated like Ganymede, Titan & Dione, rather than homogenous like Callisto & Rhea)??? Andrew Brown.  <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

UFmbutler · Dec 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Hi UFmbutler, That would be the logical approach. However no one alive today can do it as the orbital period is 892.5 years. Yes it does seem likely that 2005 QU182 is mostly rocky as are Eris, Pluto & Haumea.Any changes on albedo are almost certainly frosts condensing onto to the surface from a thin 'atmosphere' crashing out onto the surface.There may be cryovolcanism of the sort seen on Enceladus & Triton & suspected now for Eris, Quaoar & Charon (maybe Pluto), rather than high temp volcanism as on Earth & Io. 2005 QU182 is a large body, certainly more than large enough to have cryovolcanism. It's just does 2005 QU182 actually have it? I suspect the increase in albedo is an 'atmosphere' frosting out onto the surface.As 2005 QU182 has passed perihelion during this 892.5 'year', that seems more likely. Andrew Brown.  Posted by 3488</DIV>Yeah, I should have stopped and thought a little bit about the orbital period...also when I said rocky I meant some solid combination of rock, silicates, ices, etc.  Nevertheless it is an interesting finding, as half a magnitude shift is pretty big.  This is really far out in the future but with the advent of things like TPF-C that(supposedly, if it ever exists) will be able to directly image earth mass planets, maybe we'll see similar changes in terrestrial exoplanets and be able to infer something about the atmospheric composition...maybe <div class="Discussion_UserSignature"> </div>

Boris_Badenov · Dec 7, 2008

Has the possibility of an impact been considered in the increase in albedo? <div class="Discussion_UserSignature"> <div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div> </div>

MeteorWayne · Dec 7, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Has the possibility of an impact been considered in the increase in albedo? Posted by boris1961</DIV> That's a pretty good idea, although the odds are low, it might well explain it.Either that, or somebody turned on the lights

<div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

3488 · Dec 7, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Has the possibility of an impact been considered in the increase in albedo? Posted by boris1961</DIV>Hi Boris, great idea. I had not thought of it. An impact would most likely leave a large area covered in fresh 'clean' ice, surrounding the new crater. Whilst the odds are very low, it is certainly highly credible & should be very seriously considered.  Replying to: <DIV CLASS='Discussion_PostQuote'>That's a pretty good idea, although the odds are low, it might well explain it.Either that, or somebody turned on the lights

Posted by MeteorWayne</DIV>It's an extremely good idea. Yes the odds are very low, but is definitely well within the realms of possibility. I had not considered it, but could well be true.Andrew Brown.  <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Dec 7, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Hi Joel, I thought Pluto & Eris were thought to be approx 75% by mass silicate rock with ice mantles / crusts surrounding said rocky cores (assuming they're differentiated like Ganymede, Titan & Dione, rather than homogenous like Callisto & Rhea)??? Andrew Brown.  Posted by 3488</DIV>hi Andrew,This is what is currently thought. But note that a density of about 2 (as expected  for Pluto, Eris, Ceres) or lower (for most TNOs, excepted Haumea) means that ices are majoritary in volume. I think this qualifies them for the appellation "icy body" (Ganymede, Titan have too a density of about 2), as opposed to "rocky bodies" like the Moon, Mars, Vesta, Io or Mercury.I would believe indeed they are at least partially differentiated, and 2005QU182 as well. Oh, btw, Callisto should be partially differentiated too (at least the outer layers, with a layer of water between ice and the non-differentiated area in the core). If you remember this thread, and if we give gredit to the author of the paper: http://www.space.com/common/community/forums/?plckForumPage=ForumDiscussion&plckDiscussionId=Cat%3ac7921f8b-94ec-454a-9715-3770aac6e2caForum%3ad148ee4c-9f4c-47f9-aa95-7a42941583c6Discussion%3a4a024b53-aa01-40b4-9f78-5e1ea1ab65ef&plckCategoryCurrentPage=0... densities of about 2 would require the radius to be above 500km for extant liquid water to have survived today, in depth... So if the actual diameter of 2005QU182 could approach 1000km, that would add it to the list of subsurface-oceaned bodies.I do believe that the likeliest explanation for revision of H at 3.1 is better orbitography, not a physical phenomenon. That already occured in the past for other TNOs. But, one never knows =>to be monitored.Best regards.

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