[meteorite-list] A New Nearby Oddball Planet

Mon May 2 23:54:09 EDT 2011

Richard, List,

Ok, here goes...

The mass of the planet? Well, there's a slight "wobble"
of a star caused by the gravitational pull of the planet.
The extent of this movement can be used to estimate
the planet's mass as a proportion of the stellar mass -
which itself is another estimate based on the star's
spectral characteristics and the star's luminosity once
we know the star's distance from Earth which we know
by parallax and other techniques.

The Hertzsprung-Russell equation (boy, I hope I spelled
that right!) relates the mass of the star to its luminosity
and color:
http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html
So, once we have a handle on the star's mass, we can
translate the "wobble" into what planet mass it would
take to make that amount of "wobble."

OK, we got the mass of the planet down.

Now, when the planet crosses the face of the star, it
causes a tiny reduction in the strength of the light
and that tiny reduction is proportional to the size of
the disc of the planet compared to the disc of the star.
If the star dims by 0.0001%, the the area of the planet
is 0.0001% of the area of the star.

And we can measure the angular diameter of the star's
disc. And because we know the distance to the star, we
can can calculate the physical diameter of the star from the
angular diameter. And from that we can calculate the
diameter of the planet in actual physical terms. And,
once we have the planet's diameter and mass, we can
calculate the density of the planet.

All you need is a ream or two of paper and a jar of
sharp No. 2 Ticonderoga pencils.... Yes, there is some
error introduced, or more correctly, a range of answers,
but that density of 11.0 is very unlikely to actually be
as low as the density of iron (8-ish) and just as likely
to be a higher density than a lower one.

Sterling K. Webb
---------------------------------------------------------------------------
----- Original Message ----- 
From: "Richard Montgomery" <rickmont at earthlink.net>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>; "Meteorite List" 
<meteorite-list at meteoritecentral.com>
Sent: Monday, May 02, 2011 8:12 PM
Subject: Re: [meteorite-list] A New Nearby Oddball Planet

> Neophyte question again, from someone with a sharp interest and a lack 
> of astophysic knowledge:
>
> In short, how can we determine the density of a planet, other than 
> ours and the locals...??  I can do it for gold-quartz samples 
> (fortunately, the other reason for metal-detectors in the filed 
> :>) )...but I need terrestrial gravity to pull it off.
>
> Always ready for a lesson,
> Richard Montgomery
>
> ----- Original Message ----- 
> From: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
> To: "Meteorite List" <meteorite-list at meteoritecentral.com>
> Sent: Monday, May 02, 2011 3:44 PM
> Subject: [meteorite-list] A New Nearby Oddball Planet
>
>
>> Back in January, there was a List discussion of a planet
>> of the Kepler 10 (unnamed) star which has a density of
>> 8.8, as heavy as iron and an argument about whether
>> an entirely iron planet could exist and how.
>>
>> Now we have a (roughly) terrestial planet with a density
>> of 11.0, or about the density of a solid lead ball... Iron
>> ain't gonna do it.
>>
>> http://www.space.com/11544-densest-alien-planet-55cancrie.html
>>
>> Nearby Alien Planet Nearly Dense as Lead
>>
>> Astronomers have pinned down some details of an
>> exotic nearby alien planet that's almost as
>> dense as lead.
>>
>> The exoplanet, called 55 Cancri e, is 60 percent
>> larger in diameter than Earth but eight times
>> as massive, researchers revealed Friday (April 29).
>> That makes the alien world the densest solid planet
>> known -- twice as dense as Earth. [2 x 5.5 = 11.0]
>>
>> Astronomers previously thought 55 Cancri e took
>> about 2.8 days to orbit its parent star. But the
>> new study reveals that the exoplanet is so close
>> to its host star that it completes a stellar lap
>> in less than 18 hours.
>>
>> "You could set dates on this world by your wristwatch,
>> not a calendar," study co-author Jaymie Matthews,
>> of the University of British Columbia, said in a statement.
>>
>> Updating views of 55 Cancri e:
>>
>> The super-dense alien world is part of a multiplanet
>> solar system about 40 light-years from Earth, in the
>> constellation Cancer (The Crab). Its sunlike parent
>> star, 55 Cancri, is bright enough to be seen from
>> Earth by the unaided eye, researchers said.
>>
>> This wide-angle photograph of the night sky shows
>> the location of 55 Cancri, a star where astronomers
>> have found five planets, including a hot, dense
>> super-Earth.
>>
>> This wide-angle photograph of the night sky shows
>> the location of 55 Cancri, a star where astronomers
>> have found five planets, including a hot, dense
>> super-Earth.
>>
>> Since 1997, astronomers have discovered five planets
>> circling 55 Cancri (including 55 Canrci e in 2004).
>> All five alien worlds were detected using the so-called
>> radial velocity -- or Doppler -- method, which looks
>> for tiny wobbles in a star's movement caused by the
>> gravitational tugs of orbiting planets.
>>
>> Initially, astronomers thought 55 Cancri e had an
>> orbital period of about 2.8 days. But last year,
>> two researchers -- Harvard grad student Rebekah
>> Dawson and Daniel Fabrycky of the University of
>> California, Santa Cruz -- re-analyzed the data.
>> They suggested that the alien planet might actually
>> zip around its host star much faster than that.
>>
>> So Dawson and Fabrycky joined up with a few others
>> to observe 55 Cancri e more closely. The team trained
>> Canada's MOST (Microvariability & Oscillations of STars)
>> space telescope on the planet's star, then watched
>> for the tiny brightness dips caused when 55 Cancri e
>> passed in front of -- or transited -- it from the
>> telescope's perspective.
>>
>> This is the same technique used by NASA's prolific
>> Kepler space observatory, which has found 1,235
>> alien planet candidates since its March 2009 launch.
>>
>> The team found that these transits occur like clockwork
>> every 17 hours and 41 minutes, just as Dawson and
>> Fabrycky had predicted. The starlight is dimmed by
>> only 0.02 percent during each transit, telling the
>> astronomers that the planet's diameter is about
>> 13,049 miles (21,000 kilometers) -- only 60 percent
>> or so larger than Earth.
>>
>> Using this information, the researchers were able to
>> calculate 55 Cancri e's density.
>>
>> "It's wonderful to be able to point to a naked-eye
>> star and know the mass and radius of one of its planets,
>> especially a distinctive one like this," said study
>> lead author Josh Winn of MIT.
>>
>> The research was released online Friday at the website
>> arXiv.org, and it has been submitted for publication
>> in The Astrophysical Journal Letters.
>>
>> A scorching-hot world
>>
>> Because 55 Cancri e is so close to its parent star,
>> it wouldn't be a very pleasant place to live.
>> Temperatures on its surface could be as high as
>> 4,892 degrees Fahrenheit (2,700 degrees Celsius),
>> researchers said.
>>
>> "Because of the infernal heat, it's unlikely that
>> 55 Cancri e has an atmosphere," Winn said. "So this
>> is not the type of place where exobiologists would
>> look for life."
>>
>> If you could somehow survive the heat, however,
>> the view from the planet's surface would be
>> exotic and spectacular.
>>
>> "On this world -- the densest solid planet found
>> anywhere so far, in the solar system or beyond -- 
>> you would weigh three times heavier than you do
>> on Earth," Matthews said. "By day, the sun would
>> look 60 times bigger and shine 3,600 times brighter
>> in the sky."
>>
>> But the appeal of 55 Cancri e is not limited to
>> such gee-whiz factoids. Because it's so close to
>> Earth, the planet and its solar system should
>> inspire all sorts of future work, researchers said.
>>
>> "The brightness of the host star makes many types of
>> sensitive measurements possible, so 55 Cancri e is
>> the perfect laboratory to test theories of planet
>> formation, evolution and survival," Winn said.
>>
>> ------------------------------------------------------------------------
>>
>> With a surface temperature of nearly 5000F (or ~2700K),
>> this can't be a lead world -- it would have boiled away by
>> now. A solid iron planet would just barely survive -- iron
>> boils at 3134K.
>>
>> A planet of 75% iron with a 25% crust of Tungsten would
>> have a density of 11, and I suppose that if everything less
>> refractory than tungsten had boiled away, you could get
>> such a planet...
>>
>> Here's everything heavier than iron and its density.
>>
>> I got tired of entering boiling points but you can see
>> that the dense elements have high boiling points...
>>
>> Boiling points alone do not tell the story; vapor
>> pressures are high above the melting point and
>> such elements could slowly escape.
>>
>> Tungsten is the best bet. MP 3680K, BP 5828K.
>> and moderately abundant in the universe, about
>> like uranium.
>>
>> 76 Os Osmium  22.61 BP 5285K
>> 77 Ir Iridium  22.56   BP 4701K
>> 78 Pt Platinum  21.46   BP 5869K
>> 75 Re Rhenium  21.02    BP 5869
>> 93 Np Neptunium  20.45   BP 4273K
>> 94 Pu Plutonium  19.84   BP 3501K
>> 79 Au Gold  19.282   BP 3129K
>> 74 W Tungsten  19.25   BP 5828K
>> 92 U Uranium  18.95  BP 4404K
>> 104 Rf Rutherfordium  18.1
>> 73 Ta Tantalum 16.654   BP 5731K
>> 91 Pa Protactinium  15.37
>> 98 Cf Californium  15.1
>> 97 Bk Berkelium  14.79
>> 95 Am Americium  13.69
>> 80 Hg Mercury  13.5336
>> 96 Cm Curium  13.51
>> 99 Es Einsteinium  13.5
>> 72 Hf Hafnium  13.31
>> 45 Rh Rhodium  12.41
>> 44 Ru Ruthenium  12.37
>> 46 Pd Palladium  12.02
>> 81 Tl Thallium  11.85
>> 90 Th Thorium  11.72
>> 43 Tc Technetium  11.5
>> 82 Pb Lead  11.342
>> 47 Ag Silver  10.501
>> 42 Mo Molybdenum  10.22
>> 89 Ac Actinium  10.07
>> 71 Lu Lutetium  9.84
>> 83 Bi Bismuth  9.807
>> 69 Tm Thulium  9.321
>> 84 Po Polonium  9.32
>> 68 Er Erbium  9.066
>> 29 Cu Copper  8.96
>> 28 Ni Nickel  8.912
>> 27 Co Cobalt  8.86
>> 67 Ho Holmium  8.795
>> 48 Cd Cadmium  8.69
>> 41 Nb Niobium  8.57
>> 66 Dy Dysprosium  8.55
>> 65 Tb Terbium  8.229
>> 64 Gd Gadolinium  7.895
>> 26 Fe Iron  7.874
>>
>> You put together a planet from the list...
>>
>>
>> Sterling
>>
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