Hi,
The heavyweight is about as heavy as you can
get without turning into a small star:
> the newly discovered planet is about 1.18 times
> brighter than Jupiter and 8.2 times as massive.
When they say "slightly bigger than Jupiter,"
they are apparently assuming it is 1.18 times
brighter than Jupiter because it has that much
more surface area. This would give it a diameter
1.086 greater than that of Jupiter (and a volume
1.28 greater than Jupiter).
> ...it's mostly made of hydrogen.
With a mass of 8.2 Jupiters in a volume 1.28
greater than Jupiter, that makes the planet's density
6.4 times greater than Jupiter's. Since Jupiter's
density is about 1.33 gm/cm^3, the density of
this planet is 8.1 gm/cm^3, or roughly about the
density of an iron meteorite. How could it be
made of hydrogen, the lightest substance in the
universe?
The density of hydrogen at 2,800,000 atmospheres
of pressure is only 1.03, about the density of water;
it's a long way from being as dense as iron. But,
somewhere in that pressure range, hydrogen turns
into a metal. Jupiter must have 100's of Earth masses
of metallic hydrogen (since it has a vigous magnetic
field), but the density of metallic hydrogen is only
1.3 gm/cm^3, still a long way from being as dense
as iron.
This all fits very nicely -- for Jupiter. Its density
(which is 1.33 gm/cm^3) is only slightly greater than
that of metallic hydrogen's, so obviously Jupiter is
largely metallic hydrogen. To say that it is "metallic"
hydrogen means only that the atoms are finally
squeezed together so closely that hydrogen's one
electron can get confused about which nucleus is
"its mommy" and can wander off (and be replaced
by a neighboring electron) and so conduct electricity.
Solid metallic hydrogen does not compress much,
but liquid metallic hydrogen is much more compressible.
It will double in density if you apply a mere 4670 billion
kg/m^2 of pressure. That makes it about 2000 times less
compressible than water. (Everybody thinks water is
incompressible, but at the bottom of the deepest ocean
trenches, the density of water is more than 4% greater
than at the surface!)
The interior pressure of this planet must be truly
phenomenal, but still it is not enough to ever squeeze
all that hydrogen so tightly that their nuclei combine in
fusion reactions, making it a star. At eight Jupiter masses,
it's too "tiny" to be even the weakest dimmest star. That
takes about 12-13 Jupiter masses.
Because its star, HD 147506, is bright and not too far
away, this source: http://oklo.org/ says "there will be all
sorts of opportunities for detailed follow-up." We can
expect a lot of big instruments to be turned its way (like
the Spitzer).
Some feel for the tremendous pace of these discoveries
can be gained by the fact that the news of the heavyweight
was still be posted at various websites when ANOTHER
new extrasolar planet was discovered!
http://exoplanet.eu/planet.php?p1=XO-2&p2=b
Sorry, Marcin, it's not a meteorite, only another
lousy planet! :=)
Sterling K. Webb
--------------------------------------------------------------------
----- Original Message -----
From: "Sterling K. Webb" <[EMAIL PROTECTED]>
To: "Meteorite List" <meteorite-list@meteoritecentral.com>
Sent: Wednesday, May 02, 2007 12:55 PM
Subject: [meteorite-list] Astronomers Find Extrasolar Planet
HeavyweightChamp
Hi, List,
Last week, the lightest extrasolar planet;
this week, the heaviest!
Sterling K. Webb
---------------------------------------------------
http://www.space.com/scienceastronomy/070502_supermassive_planet.html
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