[meteorite-list] Habital Planet Discovery Announcement

From: Katsu OHTSUKA <ohtsuka_at_meteoritecentral.com>
Date: Thu, 30 Sep 2010 13:01:10 +0900
Message-ID: <E41A13B0F74D4EC8A2E14DC668ED2056_at_KATSU>

Its preprint is in arXiv.org
http://lanl.arxiv.org/abs/1009.5733

Katsu
----- Original Message -----
From: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
To: <countdeiro at earthlink.net>; <meteorite-list at meteoritecentral.com>
Sent: Thursday, September 30, 2010 11:27 AM
Subject: Re: [meteorite-list] Habital Planet Discovery Announcement


Hi, Count, List,

Also reported here:
http://www.space.com/scienceastronomy/earth-like-exoplanet-possibly-habitable-100929.html

    The finder is excessively enthusiastic about the chances
of life. There are problems with a three-earth-mass. It
will not be like a Big Earth. It's more complicated than
that. (The Yahoo article has the mass wrong, BTW.)

   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 as the Earth, only more so? Nope,
more of the same is definitely not the same.

   If the Earth were bigger, 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 and
bigger Earth.

   Since the solid crust of a larger "Earth" would be
much thinner, heat transfer to the surface much faster,
vulcanism much livelier, plate tectonics much zippier.

   This "Earth" has a diameter 1.40 times that of our Earth:
11,200 miles across. It would have twice the surface area,
2.75 times the volume, and 3 times the mass (compressibility
squishes). It's surface gravity would be 51% greater. If the planet
is four Earth masses, its diameter would be 1.58 times the
Earth's without accounting for compressibility and about
1.50 to 1.53 Earth radii squished. Its surface gravity would
be 73% greater than the Earth's, in that case.

But I'll continue to calculate based on three E-masses...

   Because it would have 3 times the water but only two
times the surface, the average ocean depth would be about
4500 meters! The pressure at the depths of these oceans
would be about 9000 atmospheres. The highest mountains
possible would be about 4000 meters (calculating from the
median diameter), so if you were the greatest mountain
climber on this Super Earth, standing on the top of Super
Earth's highest mountain, you would still have 500 meters
of water above you!

   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 Super Earth would be about 60 km thick, but
the lithosphere would only be about 40 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 Super Earth's silicate crust would be
recylced very rapidly with lots of local vulcanism and lots of
"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.

      So a bigger Earth is not just a bigger Earth. Knowing that
somebody will ask how much bigger a bigger Earth has to be
before there's no land at all, just oceans, the answer is:
somewhere between 2-1/2 and 3 Earth masses is the point
where the median ocean depths equal the height of the
highest possible mountain.

   Whoops! No continents. This Super Earth is a WaterWorld!
Possibly very few islands. That's serious. It means "No Surfing,"
because there's no land for the waves to break on. It's almost
certain that it would have more water than our Earth, because
the star is metall-poor (see below).

     A red dwarf is a main sequence star: once a dwarf, always a
dwarf. It's just a low-mass star with a longer lifetime (25 billion
years?) than our Sun (10 billion years?). At a third of a solar
mass, it's got a respectable little "heliosphere" and all the
usual solar (or stellar) apparatus, just less extensive than a
G0 dwarf star like us. But it doesn't have as big a system to
fend outside radiation away from.

In general, M-class star systems seem to be quiet places.
Some theorists regard smaller stars as safer places (sort of
like being a stellar mouse; just keep quiet and no one will
notice you). M-class dwarfs are very, very common and often
very old, but their age is often hard to determine. [Their
stellar atmosphere is full of diatomic molecules and their
spectra are, like, scrambled eggs!]

    I looked for information on the star itself, Gliese 581:
http://www.solstation.com/stars/gl581.htm
    "Gliese 581 is a cool and dim, main sequence red dwarf
(M2.5 V). The star has almost a third (31 +/- 2 percent)
of Sol's mass, possibly 29 percent of its diameter, and a
bit more than one percent (around 0.013) of its visual
luminosity..."

    The composition of the Super Earth may be different,
too. "The star appears to be only around 47 to 56 percent
as enriched as Sol in elements heavier than hydrogen ("metals")...
Its kinematic characterisitcs, magnetic activity, and sub-Solar
metallicity indicate that Gliese 581 is at least two billion
years old. Gliese 851 is a variable star with the designation
HO Librae."

    I don't like that "variable" part, do you? Less heavy
elements means a half the iron, half the oxygen, silicon,
carbon, you name it... And conversely, lots of volatiles,
maybe more ocean than I calculated, possibly a thicker
atmosphere.

    Gliese 581 has its Wikipedia entry, of course, and Planet G
is already there: its mass is ?3.1 Earth masses; it orbits at
0.14601 ? 0.00014 AU; its year is 36.562 ? 0.052 days. The
orbit has approximately 0.0 eccentricity. Well, maybe.
http://en.wikipedia.org/wiki/Gliese_581

    It's just like show business: yesterday, you were a nobody
and today, you're a Star!

    Gliese 581 is about 1/3rd of the mass of the Sun, which
means that it is only 0.037 the luminosity of the Sun, a
mere 3.7%. Gliese 581 is a neighbor, only 20.4 light years
away, one of the 100 closest stars.

    The newly discovered planet is 0.146 AU from the star,
about 13,578,000 miles, and takes only 36.562 days, or
877.5 hours, to orbit its star.

    If it seems to you that it must be rather dim on Gliese 581g,
with a star only 3.7% of the brightness of the Sun... think
again! At 0.146 AU, a star is 46.9 times brighter than it is at
1.0 AU, so it's fortunate that the star is only 3.7% of the
brightness of our Sun, because "sunlight" on Gliese 581g is
a mere 173% BRIGHTER than sunlight on Earth. Accounting
for all the factors, the solar energy at the planet should be
about 75% greater than the Earth's also.

    And lastly, they are likely wrong about the planet being
tidally locked to face the star. As a close planet rotates and
slows by tidal forces acting on it, there is a "trap" at the 3:2
resonance, which is so strong that it stops the slowdown.
The planet likely has a "day" 54.843 days long. But it will
even out those temperature extremes. I predict strong storm
systems transferring heat and moisture from the "summer"
hemisphere to the "winter" hemisphere.

    See, we already know something about space travel to
Gliese 581g! Take sunglasses, some really good rain gear,
many, many watercraft, and leave the surfboard at home.
And if we've learned to talk to dolphins and whales by the
time we go, we might consider asking them to join the crew...
Depends on what the probes find.

    If there's intelligent life, it may be expecting us someday.
In October 2008, members of the networking website Bebo
beamed A Message From Earth, a high-power transmission at
Gliese 581, using the RT-70 radio telescope belonging to the
National Space Agency of Ukraine. This transmission is due
to arrive in the Gliese 581 system's vicinity by the year 2029;
the earliest possible arrival for a response, should there be
one, would be in 2049.


Sterling K. Webb
----------------------------------------------------------------------------------
----- Original Message -----
From: countdeiro at earthlink.net
To: meteorite-list at meteoritecentral.com
Sent: Wednesday, September 29, 2010 6:37 PM
Subject: [meteorite-list] Habital Planet Discovery Announcement


> Hello List,
>
> Maybe...just maybe...
>
> http://news.yahoo.com/s/afp/20100929/sc_afp/usastronomyplanet_20100929210707
>
> Best to all,
>
> Count Deiro
> IMCA 3536
>

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Received on Thu 30 Sep 2010 12:01:10 AM PDT