[meteorite-list] OT: New Smallest, Possibly Earth-like,Extra-Solar Plane...

From: Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Wed Jun 15 19:40:05 2005
Message-ID: <016a01c57203$82eb8a70$2f01a8c0_at_Dell>

  But trying to find a nearby "invisible" star is a truly daunting technical
problem
concerning which no light bulbs have turned on in my brain... It's as dim
in there as
the L dwarves themselves!


Sterling K. Webb
infared won't detect the L's??? Jerry Flaherty
----- Original Message -----
From: "Sterling K. Webb" <kelly_at_bhil.com>
To: <MexicoDoug_at_aol.com>
Cc: <meteorite-list_at_meteoritecentral.com>
Sent: Tuesday, June 14, 2005 4:22 PM
Subject: Re: [meteorite-list] OT: New Smallest, Possibly
Earth-like,Extra-Solar Plane...


> Hi,
>
> My example of a SuperEarth was based on taking the same materials (bulk
> composition) as the Earth is made from and just piling more of them
> together. We have
> no idea (and no way of knowing, for now) if the planetesimals of the
> Gliese 876 system
> were the same mix as the Sol planetesimals, but we think the raw materials
> of solar
> systems are generally similar.
> When I started suggesting the loss of some water so we could have
> continents and a
> higher albedo so it would be cooler and so forth, you were being treated
> to an ugly
> display of a rational mind crumbling under the pressures of "interstellar
> optimism,"
> the desire to improve things just a touch.
> After all, planetary systems have unique histories. The Earth picked
> up this
> whonking huge Moon to stabilize its axis and its climate though blind luck
> at
> incredible odds. Mars got all these volariles (we think) but then got its
> atmosphere
> stripped off and died. Venus really got a dirty deal; don't know what it
> was, but it
> was nasty. Them's the breaks.
> It does make it look like there's more planetary bad luck than good
> luck, doesn't
> it? I'm sure we all wish Europa well! And I have a soft spot in my head
> for Titan.
> Always have had...
> The interstellar "optimists" tend to think of extra-solar worlds as
> similar to what
> we know, but 50-60 years ago the interplanetary "optimists" tended to
> think of solar
> worlds as more Earth-like than they turned out to be.
> As a teenager in the early Fifties, I devoured every scientific book on
> other
> planets that there was, and the picture they presented was rosy compared
> to reality,
> The very best book on Mars, "The Physics of the Planet Mars," by the great
> Gerald de
> Vaucouleurs, was translated in English in 1953, a substantial tome filled
> with
> equations, graphs, and tables. I special ordered it, and it was damned
> expensive.
> It presented a Mars with an atmospheric pressure of 100 to 200
> millibars and 85
> degree F. noonday temperatures. All the astronaut would have to do was
> slip on flight
> mask with a 10 pound oxygen tank on his back and go for a stroll. He
> could leave his
> leather jacket and white scarf back in the rocket because it's comfortable
> weather out
> there, at least in the daytime.
> The notions of Venus were rosier still. It seems that the less you
> know, the
> happier the picture you get.
> Here's the kind of paradox that arises from "happy" thinking. Venus
> gets twice as
> much solar energy as the Earth. But the albedo (reflectivity for those of
> you
> listening in) of Venus is more than twice that of the Earth (as we
> estimated the
> Earth's albedo in those days), so Venus shouldn't be any warmer than the
> Earth (and a
> few brave souls even suggested it was cooler, with big polar ice caps)
> In the 1940's, Rupert Wildt measured huge fat CO2 absorption features
> in the Venus
> spectrum and concluded that Venus was a waterless inferno as hot as hell's
> hinges.
> What he got for his suggestion was a lot of scowls and being ignored for a
> decade or
> so. Other scientists (big names and I ain't saying who) measured H2O
> bands, They were
> dead wrong about the water, because the water they were measuring was in
> the atmosphere
> of Earth, not Venus! Who knew?
> So, Venus was maybe a little warm, very wet, always cloudy but bright,
> kind of like
> the Permian had been on Earth. Venus was so remarkably like the Earth on
> paper that
> everyone figured it was the twin it appeared to be. Probably had oxygen
> under those
> clouds, Get out of the spaceship, wear good boots (it was bound to be
> muddy), and keep
> an eye out for Venusian dinosaurs.
> I'm not talking about science fiction writers here; I'm talking about
> real
> honest-to-gosh scientists. We had gotten over Lowell and his canals on
> Mars, but not
> by much. Pickering was still talking about life on the Moon, for heaven's
> sake.
> Although he had a great explanation for Martian canals: they were the
> migratory routes
> of Martian herbivores, fertilized by their droppings.
> Tommy Gold had his own special heresy for Venus (doesn't he always?),
> an ocean of
> hydrocarbons, an idea that would get picked up from Venus and moved to
> Titan for 30 or
> 40 years. Ain't there.
> You don't suppose wishful thinking has anything to do with the notion
> of a
> planetary body with oceans of gasoline, do you? Nah... Sorry, no oceans
> of free
> gasoline. You can leave the SUV at home, buddy.
> In some ways, science fiction writers could be more realistic than
> scientists in
> those days. Hal Clement (Harry Stubbs) wrote two novels about life on a
> SuperJupiter
> around 61 Cyngi which are better pieces of rigorous thinking about these
> really alien
> worlds than any scientific work that had been done on the question. He
> made me think
> about eutectic melts of ammonia and water in all its complexity until my
> head really
> hurt. Of course, in those days, no one was doing scientific work on the
> question.
> Turns out the SuperJupiter around 61 Cyngi is really there! Along with
> scores of
> other SuperJupiters around other stars.
> Even more fascinating is the possibility of other kinds of stars. We
> have always
> assumed that the tiniest faint dink of an M9 star is as small as "stars"
> get. Less
> mass and you get essentially non-luminous bodies: brown dwarves, very
> brown dwarves,
> and black dwarves.
> But 2MASS (the Two Micron All Sky Survey) turned up huge numbers of
> very, very
> faint stars never seen before, too faint to be seen in visible light.
> About twenty of
> them have been assigned on their spectral characteristics to a new class
> of stars: the
> Class L main sequence stars. About six are brown dwarves. Since 2MASS
> only sampled a
> very small patch of sky chosen at random and since their low emission sets
> a limit to
> how far away we could detect these faintest of all stellar objects, we can
> calculate
> their abundance.
> The astounding answer is that they are more abundant than the M Class
> stars that we
> used to think were the most abundant, so much so that the likelihood is
> that there are
> about 2000 L Class main sequence stars within 50 light years of the Sun.
> Yes, that's
> 2000 neighboring stars to our Sun that we can't even see in visible light!
> <http://astron.berkeley.edu/~basri/bdwarfs/sec4.htm>
> <http://astron.berkeley.edu/~basri/bdwarfs/sec6.htm>
> That's an average of about one such star per 260 cubic light years.
> Hmmm... What's
> the radius of a sphere with a volume of 260 cubic lightyears centered on
> our Sun? It's
> a shade less than the distance to the "nearest star," good old alpha
> Centauri. I put
> quotes around that phrase "nearest star" because, if 2MASS is right (and
> it seems to
> be), there is a good chance there's an "invisible" star just as close or
> closer to the
> Sun than that star we can see!
> Really big bright stars don't seem to have planets. They gobble up all
> the planet
> food and blow off the rest; it too energetic an environment for a solar
> system to form
> in. We used to think low-mass stars, like M class, wouldn't have planets
> because there
> wasn't enough mass around, but the detections of extra-solar planets seem
> to indicate
> that the formation of a less energetic star leaves plenty of material left
> over for
> planets. Little Gliese 876 has two SuperJupiters!
> So, following that line of reasoning, why wouldn't the new L Class
> stars have lots
> of planets too? Despite the fact that "happy" thinking would like alpha
> Centauri to
> have planets because it's the closest, hence easiest, star to get to, no
> detection
> attempt has ever found any hint of planets. A closer L Class main
> sequence star with
> planets would genuinely be worth looking for!
> But trying to find a nearby "invisible" star is a truly daunting
> technical problem
> concerning which no light bulbs have turned on in my brain... It's as dim
> in there as
> the L dwarves themselves!
>
>
> Sterling K. Webb
> ------------------------------------------------------
> MexicoDoug_at_aol.com wrote:
>
>> Hola Sterling,
>>
>> Your Super-Earth got me thinking about viable life forms though I'm not
>> yet
>> too adjusted. There certainly will be continents, though they will be
>> floating quagmires of life and useful excreta, and will probably get
>> quite thick.
>> Easily enough to walk on, despite those who worry about finding a
>> surface on
>> such gas-liquid giant planets. Not that walking will be too easy, so I
>> guess
>> you would need bigger muscles to deal with that. The interesting thing
>> with
>> such a world is there would be several interfaces - multilevel
>> continents -
>> especially suitable as anchors (surfaces) for life depending on the
>> vertical
>> profile of gases and liquids present. Gravity might be similar to that
>> on
>> Earth believe it or not, or even less in some of the upper level
>> continents
>> since the rarification will reduce the gravitational acceleration by the
>> height
>> squared (If you are on a planet 8 times the mass of earth but at 2.8X
>> the
>> radius, "surface gravity" is the same as Earth.)
>>
>> But you're right it would get stuffy, so life would probably be pretty
>> acuatic-like and evolution driven by the rise to an upper or lower
>> continent in
>> addition to competition for low hanging fruit resources. There would
>> probably
>> be heavy development using bouyancy, and things would probably fly in
>> that
>> fashion. So the mosquitos you would swat would land on you by
>> regulating their
>> body densities with intestinal waste gas. Yuck.
>>
>> Dense Ice would be at least down where pressures (and depths) were at
>> 3000
>> atm, and very unstable given the dynamics of the situation, it would be
>> more
>> like a cloud formation, as probably not to present much of an issue.
>> But the
>> sort of magnetosphere this planet would have...could metallic hydrogen
>> make
>> it Earth-like? Probably too small. It would be a pretty boring place,
>> though
>> as meteorites would not be much less likely than on the surface of ...
>> Venus... so I guess these water breathing nitrogen-fixing creatures
>> would do
>> something else for kicks (Starlight would not be very plentiful - and we
>> need a
>> renewable energy source or biosphere equilibrium with net energy going
>> into
>> support the net entropy production of the system).
>>
>> What I wonder is how the higher forms would generate and harness
>> electricity
>> for progress, considering the whole planet is sounding rather grounded
>> in a
>> lightening sauna? It would make for a hell of a set of oceanmill farms
>> working off the sea currents for anyone who could come up with a good
>> insulator...
>>
>> Saludos, Doug
>>
>> Sterling W. wrote:
>> Hi,
>>
>> Is this an all time high or an all time low? I'm replying to
>> my own post (see below)!
>> While I don't have the most recent edition, I dug out my copy of
>> "Planetary Engineers' Handbook" (Dresden, 15th Ed., 2314 AD) to
>> investiigate the characteristics of a "SuperEarth." Here's what
>> I found:
>> So, what would a SuperEarth be like? If you start with the
>> same recipe mix of ingredients as the Earth and just made a
>> bigger batch of planet, is it just the same, only more so? Nope,
>> more of the same is not the same.
>> If the Earth were bigger, it would retain more volatiles to
>> begin with. But in addition, the volume of water would
>> increase faster than the increase in surface area, so the
>> oceans would be deeper. Because of the deeper oceans and the
>> greater gravity, the pressures at the bottoms of those oceans
>> would be much higher.
>> Continents and their mountains would be much lower, because
>> the temperatures in the crust would increase faster with depth,
>> until the fluid point would be reached in the crust instead of
>> the mantle like it is on "our" Earth. Mountains can only pile
>> up until the pressures under them are about 3000 to 3500
>> atmospheres, and that zone would be reached at shallower and
>> shallower depths on a bigger Earth.
>> The solid crust of a larger "Earth" would be much thinner,
>> heat transfer to the surface much faster, volcanism much
>> livelier, plate tectonics much zippier.
>> Imagine an "Earth" exactly twice the diameter of our Earth:
>> 16,000 miles across. It would have four times the surface,
>> eight times the volume, and 12 times the mass (compressibility
>> squishes). It's surface gravity would be 3 times greater. The
>> escape velocity from the surface would 2.45 times greater.
>> Because it would have 12 times the water but only four
>> times the surface, the average ocean depth would be about 9000
>> meters! The pressure at the depths of these oceans would be
>> about 3000 atmospheres. The highest mountains possible would be
>> about 4000 meters (calculating from the median diameter), so if
>> you were the greatest mountain climber on the SuperEarth,
>> standing on the top of SuperEarth's highest mountain, you would
>> have 5000 meters of water above you!
>> Whoops! No continents. The SuperEarth is a WaterWorld.
>> On our Earth, the crust is about 30 kilometers thick, but
>> the lithosphere (rocks that stay stiff and not slushy and
>> slippy) is about 75 kilometers, so the Earth's lithosphere
>> contains all the crust and the top part of the mantle.
>> The crust of the SuperEarth would be about 90 km thick, but
>> the lithosphere would only be about 30 kilometers thick. This
>> means that it would be very difficult to sink pieces of crust
>> (subduction) and equally difficult to bring deep basalt magmas
>> to the surface.
>> On the other hand, the SuperEarth's silicate crust would be
>> recylced very rapidly with lots of local vulcanism and
>> "hotspots" and have a very similar composition everywhere. The
>> only weathering that would be possible would be chemical,
>> because all the volitiles are released into the oceans rather
>> than the atmosphere.
>> The only question we can't answer is how hot or cold a
>> SuperEarth would be, since that depends on the distunce to its
>> Sun. Too far away and the oceans turn to ice, even Ice III,
>> which sinks instead of rising. Wow, did you know that?.
>> Too close and the oceans boil away, creating a
>> SuperVenus. But I discover that making a Super Venus is
>> not as easy as it sounds. It's very hard to strip all that
>> atmosphere and immense oceans of volatiles away from a
>> planet that has an escape velocity of 27,400 meters per
>> second!
>> And remember, a SuperEarth would have
>> proportionately more volatiles than a puny little Earth
>> like ours. It could even afford to lose some of those
>> 9000 meters of ocean, don't you think? Maybe
>> enough to have continents?
>> Its immense atmosphere would have a very high
>> albedo from a water cloud deck 100's of kilometers
>> deep, and the surface temperatures could well be below
>> 100 degrees C. Hmm, starting to sound interesting.
>> (Originally posted to the List 08-31-2004 in anticipation
>> of the discovery of a "SuperEarth," and Heck! I didn't
>> even have to wait a year... What next?)
>>
>> Sterling K. Webb
>> ------------------------------------------
>
>
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Received on Wed 15 Jun 2005 07:39:45 PM PDT