[meteorite-list] So many parent bodies, so few samples

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon, 11 Jun 2007 18:11:26 -0500
Message-ID: <042501c7ac7d$d6685640$c3e08c46_at_ATARIENGINE>

Hi, Darren, List,

> exact solar system analogs and we wouldn't know it because
> we haven't been able to take data for long
> enough to actually find their planetary systems...

    I'd like to be wrong, but I think it's going to be
a long wait. Let's say you're dozens of light years
away from us and luckily, you're in the plane of the
planets. You set up your automatic giant telescope
system and wait for the Earth to cross in front of
The Sun.

    The Earth is only 1/100th of the diameter of the
Sun and so only blocks 1/10000th of the Sun's light.
So you're waiting for up to 365 days for the Sun to
dim by 0.01%. Of course, there are sunspot clumps
that dim the Sun that much but they take days to
cross the Sun. So, you can distinguish between
a big sunspot and a terrestrial planet no matter how
far out it is.

    The Earth will only take less than thirteen hours to
cross the Sun's disc when viewed from far away.
But the problem of "spotting" the Earth is nothing
when compared to catching Mercury! Mercury will
only dim the Sun by about a 1/10th of the amount
the Earth will, or 0.001% for less than eight hours.
Good luck, alien planet hunters! Fortunately for you,
there's bigger game to hunt.

    Yes, it's the Solar System's Big Boy -- Jupiter --
that catches all the attention. It will dim the Sun by
almost 1% and the dimming transit will last 30 hours.
Jupiter will be the Catch of the Day for an alien planet
hunter. But it may not be the first to be discovered
because our poor alien will have to wait for up to
almost 12 years for Jupiter to show up in his 'scope...
the first time. Just like our planet hunters, They will
go through a few full cycles of the whole system,
to be sure. That will kill most of a century.

    I hope we're worth it.

    Since the technique requires only big telescopes
(in orbit would be nice), simple automated machinery,
and LOTS of patience... Well, OK, you need to be near
the plane defined by the planetary plane of the solar
system -- that's about 3% of the stars within a given
volume. How many is that?

    Well, there's about 14,000 stars with 100 light years
(3% = 420). Hipparchos says 22,010 stars within 326
light years (3% = 660). There are 3919 Sun-like stars
(spectral type F8 through K3) within 100 light years.
These are stars very much like the Sun; if you were
standing on Earth-like planet (and were not distracted
by being on an alien planet), it would be indistinguishable
from the Sun at first glance.

    Of those 3919 stars, about 120 of them are in a place
where they can spot Our Solar System EASY -- it's like
shooting planets in a barrel... or something like that. Out
to 200 light years, that is A THOUSAND Sun-like stars
(and their planets and their aliens) that can easily find
us with such simple means as these.

    With a big orbital telescope farm and the steadfastness
we all need, detection within 1,000 light years is no problem.
There are 120,000 Sun-like stars in that volume well-placed
to find and catalog our Solar System in detail. No doubt the
systems that have suitable planets in what They think is the
habitable zone are referred to Their Big Eye scope for some
spectroscopy and visualization. Perhaps suitable candidates
go on the list for a light-sail fly-by probe.

    Let's all be on our best behavior. Who knows? THEY
may be watching. Or is it THEM?


Sterling K. Webb
----------------------------------------------------------------------
----- Original Message -----
From: "Darren Garrison" <cynapse at charter.net>
To: <meteorite-list at meteoritecentral.com>
Sent: Monday, June 11, 2007 2:52 PM
Subject: [meteorite-list] So many parent bodies, so few samples


http://www.space.com/scienceastronomy/070611_mm_planet_floodgates.html

Trickle of Planet Discoveries Becomes a Flood
By Jeanna Bryner
Staff Writer
posted: 11 June 2007
07:10 am ET

Alien worlds, once hidden from knowledge, are now being discovered in
droves,
stunning astronomers with their unique features and sheer numbers. The
discoveries are so common that more and more don't even get reported outside
scientific circles.


Take the announcement at the end of May of a massive planet, dubbed TrES-3,
that
zips around its star in an amazingly rapid 31 hours, giving the planet a
1.3-day
year. Astronomers issued a press release, but you might not have heard about
it
because the discovery was so overshadowed by other planet announcements and
barely received news coverage.


"It's pretty routine now," said Alan Boss, a planet formation theorist at
the
Carnegie Institution of Washington. "Most planets that are found are not
deemed
worthy of a press release because they are sort of becoming 'one more
planet.'"


The total is now more than 200 extrasolar planets confirmed. And this is the
tip
of the iceberg in planet finds. Astronomers have more tools than ever, and
technology is so advanced that planet discovery has become almost mundane.


The regularity of planet finds, luckily, is buffered by the wild variety in
the
discoveries themselves, including the following contrasts: nascent worlds of
just a million years versus those that are billions of years old; hot gas
giants
and icy Neptune-like orbs; planets that whip around their parent stars with
cosmic speed and others that seem to creep at a slug's pace; and planets
orbiting double-stars, red-dwarf stars and even so-called failed stars.


Transit technique


Astronomers spotted TrES-3 as part of the Trans-atlantic Exoplanet Survey
while
looking for transiting planets, or those that pass directly in front of
their
home star with respect to Earth. It was detected with a network of
telescopes in
Arizona, California, and the Canary Islands. When TrES-3 coasted in front of
its
home star, the telescopes picked up a slight dimming of the star's light, by
about 2.5 percent. The scientists used the dimming to estimate the planet's
mass, size and other properties.


It is located 800 light-years away in the constellation Hercules about 10
degrees west of Vega, one of the brightest stars in the summer skies of the
northern hemisphere.


"It is also a very massive planet-about twice the mass of the solar system's
biggest planet, Jupiter-and is one of the planets with the shortest known
periods," said a co-discoverer of TrES-3 Georgi Mandushev of the Lowell
Observatory in Arizona.


The giant orb orbits so close to its parent star, about 50 times closer than
Earth is to the Sun, the astronomers estimate its temperature soars to about
1,500 degrees Kelvin.


Stellar wobbles


While the "transit method" provides astronomers with the best indirect
information about an exoplanet, so far only about 20 transiting planets have
been spotted.


That's why the most successful (based on the number of planet finds) teams
have
relied on the so-called wobble method, or radio-velocity technique.


"The radial-velocity teams are the most successful," Boss told SPACE.com.
"They
are a victim of their own success. They are able to get more and more
telescope
time, because they can prove to the assignment committees that give out the
time
that 'if you give us so many more nights we can probably find you so many
more
planets,'" Boss said.


He added, "The key bottleneck for finding more planets is simply more time
on a
telescope."


The firsts and superlatives


In addition to finding new worlds, the burgeoning field has achieved many
firsts.


In 2001, a team led by David Charbonneau of the Harvard-Smithsonian Center
for
Astrophysics used the Hubble Space Telescope and NASA's infrared-detecting
Spitzer Space Telescope to detect for the first time the atmosphere of an
extrasolar hot Jupiter called HD 189733b.


Another hot Jupiter, Upsilon Andromeda b, revealed for the first time an
exoplanet with a temperature variation across its surface: One side has
temperatures rivaling those found deep in a volcano while the other face
could
plunge below freezing.


Superlatives abound as well, with discoveries gaining fame as the windiest,
tiniest, most massive and fastest orbiter.


Shortest orbital period in catalog: HD 41004 B b completes a full orbit in
1.328
days.

Longest orbit: HD 154345 b takes 13,100 days to orbit its parent star.

Lightest planet: Gliese 581 C weighs just five Earth masses.

Planet organizer


In an effort to keep track of the rapidly increasing list of exoplanets, a
group
of astronomers published a catalog of nearby exoplanets within 652
light-years
of Earth in a 2006 issue of the Astrophysical Journal, though they realize
updates will be a must on a routine basis.


"Without question, the catalog presented here will become out of date before
it
is printed," the researchers say in the published report of the catalog.


But with such a huge sample of relatively nearby planets, theorists now have
the
chance to test out their theories in the "real world."


"This whole business of extrasolar planets has been a real boon for
theorists
because so far they had only one planetary system to study-and that was
ours,"
Mandushev said in a telephone interview.


For instance, when does an object stop being a planet and become a star, a
threshold that theory places at 10 to 15 Jupiter masses and beyond which an
object can ignite hydrogen fusion to power a stellar glow'


The real goal


The ultimate goal, say many planet hunters, is to find Earth-like planets,
or
those with similar masses, orbits and rocky compositions to Earth. And
beyond
finding the physical Earth-like attributes would be to find life. So far no
"Earths" have been identified, though observatories are coming online with
the
sensitivity to detect small objects that orbit far from their host stars, as
our
planet does.


"The hunt is still on for rocky, Earth-like planets," said Jason Wright, an
astronomer at the University of California, Berkeley, who was part of the
team
compiling the exoplanet catalog.


And astronomers have identified the first Earth-like planet that could
support
liquid water and harbor life. The "super Earth," Gliese 581 C, weighs about
five
Earth masses and is either a rocky planet or one covered entirely by oceans,
astronomers speculate.


Multi-planet systems are also a goal. So far about 25 multi-planet systems
have
been identified with two such systems supporting four planets.


"We haven't found a clone of the solar system yet," Boss said. "But that's
only
ruling out maybe 10 percent of the stars. The other 90 percent could have
exact
solar system analogs and we wouldn't know it because we haven't been able to
take data for long enough to actually find their planetary systems."

______________________________________________
Meteorite-list mailing list
Meteorite-list at meteoritecentral.com
http://six.pairlist.net/mailman/listinfo/meteorite-list
Received on Mon 11 Jun 2007 07:11:26 PM PDT