[X] My Assistant

[ljk4-1]

Paper: astro-ph/0507422

From: Jonathan J. Fortney [view email]

Date (v1): Mon, 18 Jul 2005 21:49:23 GMT (134kb)
Date (revised v2): Tue, 3 Jan 2006 19:32:19 GMT (224kb)

replaced with revised version Tue, 3 Jan 2006 19:32:19 GMT (224kb)

Title: Atmosphere, Interior, and Evolution of the Metal-Rich Transiting Planet
HD 149026b

Authors: J. J. Fortney, D. Saumon, M. S. Marley, K. Lodders, R. S. Freedman

Comments: Accepted to the Astrophysical Journal. 18 pages, including 10
figures. New section on the atmosphere of planet HD 189733b. Enhanced
discussion of atmospheric Ti chemistry and core mass for HD 149026b

We investigate the atmosphere and interior of the new transiting planet HD 149026b, which appears to be very rich in heavy elements. We first compute model atmospheres at metallicities ranging from solar to ten times solar, and show how for cases with high metallicity or inefficient redistribution of energy from the day side, the planet may develop a hot stratosphere due to absorption of stellar flux by TiO and VO. The spectra predicted by these models are very different than cooler atmosphere models without stratospheres. The spectral effects are potentially detectable with the Spitzer Space Telescope. In addition the models with hot stratospheres lead to a large limb brightening, rather than darkening. We compare the atmosphere of HD 149026b to other well-known transiting planets, including the recently discovered HD 189733b, which we show have planet-to-star flux ratios twice that of HD 209458 and TrES-1. The methane abundance in the atmosphere of HD 189733b is a sensitive indicator of atmospheric temperature and metallicity and can be constrained with Spitzer IRAC observations. We then turn to interior studies of HD 149026b and use a grid of self-consistent model atmospheres and high-pressure equations of state for all components to compute thermal evolution models of the planet. We estimate that the mass of heavy elements within the planet is in the range of 60 to 93 M_earth. Finally, we discuss trends in the radii of transiting planets with metallicity in light of this new member of the class.

\\ ( http://arXiv.org/abs/astro-ph/0507422 , 224kb)

[ljk4-1]

This is from the latest Sky & Telescope News Bulletin, of all places.

LOOKING FOR A CREATOR'S CALLING CARD

If our universe was purposefully created -- perhaps by a deity or an
advanced civilization in another universe -- could the creator have left a
calling card in the microwave background?

The idea is not as crazy as it seems. Cosmologists such as Andre Linde
(Stanford University) and Alan Guth (MIT) have speculated that an advanced
civilization could, in principle, cook up a new universe in a lab by
concentrating huge quantities of energy into a tiny volume of space....

In a paper posted on astro-ph, physicists Stephen Hsu (University of
Oregon) and Anthony Zee (University of California, Santa Barbara) come up
with an alternative idea: astronomers could look for an artificial message
from the creator in the cosmic microwave background (CMB) -- the afterglow
of the Big Bang....

http://SkyandTelescope.com/news/article_1647_1.asp

[ljk4-1]

Active Assessment of Active SETI

by H. Paul Shuch, Ph.D.

Almost since its inception nearly half a century ago, SETI science has seen its supporters wage a running battle over the question of transmissions from Earth. Deliberate transmission of signals into space, sometimes called Active SETI, is justified by its proponents on the grounds of reciprocity. That is, some argue, we cannot in good conscience search for signals which we would hope other civilizations might choose to beam our way, if we ourselves are not willing to transmit such signals from Earth. The counter-argument involves the safety, and some would say the very survival, of our planet.

Critics to Active SETI point out the dangers of shouting in the jungle. Radio amateurs in support of Active SETI counter that (1) the cat is already out of the bag, as we have been inadvertently transmitting to the stars for a century or so, and (2) if everybody's listening and nobody calls CQ, the bands will appear dead to all concerned.

http://www.setileague.org/editor/sanmarin.htm

[Guest_Richard Trigaux_*]

The counter-argument involves the safety, and some would say the very survival, of our planet.

Critics to Active SETI point out the dangers of shouting in the jungle. Radio amateurs in support of Active SETI counter that (1) the cat is already out of the bag, as we have been inadvertently transmitting to the stars for a century or so, and (2) if everybody's listening and nobody calls CQ, the bands will appear dead to all concerned.

http://www.setileague.org/editor/sanmarin.htm

If there are other civilizations out there, and especially space faring civilizations, they know for long we are here. Why? because, whatever their motives (peaceful or agressive) they surveyed their sky for long with instruments much more powerfull.

For now we are babies in the art of interstellar communications. Only in some tens of years ahead we shall be able to detect Earth like planets at a great distance, and test if they are suitable for life.

That other civs would be exactly at the same point would be a very unlikely coincidence. Either they are much older (million years) or they don't yet exist.

So if they exist they have thousands and even millions years technology advance on us. And, as a consequence, they know for long that there is evolved life on Earth. Eventualy they put our planet on a priority list for survey, and keep constantly an ear on us, knowing that we shall one day or another use prehistory techs such as radio waves. They even may have archaeologists studying us.


Why a predatory civilization would show up right now? It is the same issue: either they were here for long (and we would not be here) or they will never come. Unlikely that they replay "independance day" right at the moment the movie is in the box office.

If they need mineral resources, they can pillage all the outer bodies of our system, which are easier to catch as they are not in a gravity well. At a pinch they could completelly dismember Mars, but never come on a planet like Earth, infected with maybe dangerous bacteria. So they could be mining Pluto right now without us noticing, and them escape lefting just strange patterns on Pluto surface.

If they need a life place, they don't need to wait for a civilization like ours to appear. We are a problem for them, even in the case they have a far more superior war technology. Anyway, any foreign life form will have to first eradicate any life form on Earth, for fear of diseases, a thing which would be very difficult (life exists in deep underground layers). So that there is perhaps less work to terraform a planet like Mars than to colonize Earth.

If they need slaves, so yes they would be interested to show right now. But why? If they have space-faring technologies they will necessarily have plenty of robots. Evolved robots are far more efficient at work that any biological worker.

The only situation which would really motivate an alien civ to attack us are psychological:
-they have some fundamentalist ideology to convert us to
-they don't like others to be happy or successful
-they like having pets, or sex slaves or for psychological games.
Here we are getting a bit nightmarish, but let us notice that such motives are really for psychologically-ill beings. Such a civilization lead by psychologically impaired persons have much weaker chances to survive their own pollution or internal wars. (And by the way it is already here...)


So I think:
-shouting our presence to others is probably safe (although we cannot know)
-It is already done anyway, so why not now to make it in an inteligent way.


Anyway we don't yet have the right technologies. Emitting powerful radio waves is expensive (much more than hearing) and sending laser rays can be done only from space. So we need a large space station in high orbit or more, powered by a very large solar plant (to collect megawatts) or a fusion reactor. Until now there was only one try at Arecibo, when emitting seriously would require a constant presence "on line". Perhaps an alien civ detected the Arecibo try, but for their SETI researchers, it was just a "wow signal" not considered seriously because it was never repeated.

[ljk4-1]

My bets are on missionaries and/or there's a major galactic construction project going on, and we're the rabbit den that will happen to be in the way.

[ljk4-1]

Astrophysics, abstract
astro-ph/0601166

From: Susanne Pfalzner Dr [view email]

Date: Mon, 9 Jan 2006 08:08:17 GMT (353kb)

Encounter-Triggered Disc Mass Loss in the ONC

Authors: C. Olczak, S.Pfalzner, R.Spurzem

Comments: 32 pages, 12 figures, 3 tables. accepted by ApJ

The relevance of encounters on the destruction of protoplanetary discs in the Orion Nebula Cluster (ONC) is investigated by combining two different types of numerical simulation. First, star-cluster simulations are performed to model the stellar dynamics of the ONC, the results of which are used to investigate the frequency of encounters, the mass ratio and separation of the stars involved, and the eccentricity of the encounter orbits. The results show that interactions that could influence the star-surrounding disc are more frequent than previously assumed in the core of the ONC, the so-called Trapezium cluster. Second, a parameter study of star-disc encounters is performed to determine the upper limits of the mass loss of the discs in encounters. For simulation times of $\sim$ 1-2 Myr (the likely age of the ONC) the results show that gravitational interaction might account for a significant disc mass loss in dense clusters. Disc destruction is dominated by encounters with high-mass stars, especially in the Trapezium cluster, where the fraction of discs destroyed due to stellar encounters can reach 10-15%. These estimates are in accord with observations of (Lada et al. 2000) who determined a stellar disc fraction of 80-85%. Thus, it is shown that in the ONC - a typical star-forming region - stellar encounters do have a significant effect on the mass of protoplanetary discs and thus affect the formation of planetary systems.

http://arxiv.org/abs/astro-ph/0601166

[Guest_Richard Trigaux_*]

Astrophysics, abstract
astro-ph/0601166

From: Susanne Pfalzner Dr [view email]

Date: Mon, 9 Jan 2006 08:08:17 GMT (353kb)

Encounter-Triggered Disc Mass Loss in the ONC

Authors: C. Olczak, S.Pfalzner, R.Spurzem

Comments: 32 pages, 12 figures, 3 tables. accepted by ApJ

The relevance of encounters on the destruction of protoplanetary discs in the Orion Nebula Cluster (ONC) is investigated by combining two different types of numerical simulation. First, star-cluster simulations are performed to model the stellar dynamics of the ONC, the results of which are used to investigate the frequency of encounters, the mass ratio and separation of the stars involved, and the eccentricity of the encounter orbits. The results show that interactions that could influence the star-surrounding disc are more frequent than previously assumed in the core of the ONC, the so-called Trapezium cluster. Second, a parameter study of star-disc encounters is performed to determine the upper limits of the mass loss of the discs in encounters. For simulation times of $\sim$ 1-2 Myr (the likely age of the ONC) the results show that gravitational interaction might account for a significant disc mass loss in dense clusters. Disc destruction is dominated by encounters with high-mass stars, especially in the Trapezium cluster, where the fraction of discs destroyed due to stellar encounters can reach 10-15%. These estimates are in accord with observations of (Lada et al. 2000) who determined a stellar disc fraction of 80-85%. Thus, it is shown that in the ONC - a typical star-forming region - stellar encounters do have a significant effect on the mass of protoplanetary discs and thus affect the formation of planetary systems.

http://arxiv.org/abs/astro-ph/0601166

Interesting indeed, as most of the stars form into such kind of regions. But it don't really affect their capability to form planets, as:
-the mass loss in only a fraction
-maybe only the outer parts of the disk are affected.



This may explain the chaotic aspect of our Kuyper belt, and its apparently abrupt end.

Eventually a star encounter may trigger the formation of the planets into an otherwise stable disk.

Such encounters may also explain "freak" systems, which contain hot Jupiters and very eccentric orbits.

[ljk4-1]

Transmitting to One Million Worlds

http://www.space.com/searchforlife/060112_...k_transmit.html

SETI researchers have typically looked at any particular star system (at a given
frequency) for only a few minutes, at most. But what are the chances that an
alien signal has been sent our way just at the right moment to splash upon our
antennas during that brief interval?


Worlds With Multiple Suns Abundant

http://www.space.com/scienceastronomy/0601...ar_planets.html

Two new studies suggest that planet formation around multiple star systems may
be more common than previously thought.

[ljk4-1]

PLANET FINDERS DISCOVER NEW WORLD WITH FAST DEVICE
--------------------------------------------------

Astronomers have discovered a planet orbiting a very young star nearly 100
light years away using a relatively small, publicly accessible telescope
turbocharged with a new planet-finding instrument.

The feat suggests that astronomers have found a way to dramatically
accelerate the pace of the hunt for planets outside our solar system.

http://spaceflightnow.com/news/n0601/11planet/


POSSIBLE COMET DUST FOUND AROUND DEAD STAR
------------------------------------------

NASA's Spitzer Space Telescope has spotted what may be comet dust
sprinkled around a white dwarf star that died approximately 500 million
years ago. The findings suggest the star, which most likely consumed its
inner planets, is still orbited by a ring of surviving comets and possibly
outer planets.

http://spaceflightnow.com/news/n0601/11cometdust/

[Guest_Myran_*]

The suggestions put forth by Mr Richard Trigaux are mostly interesting possibilities, and I agree that the cost for interstellar flight -even for one extremely advanced civilization- would be so high that it possibly would take some kind of 'grand idea' of one kind or other before they would undertake and well open the wallet for the tremendous cost.

But I would be hard pressed to accept the idea of any kind of civilization that would mine minerals in one stellar system and then ship the metals over interstellar distances.
There might be need for mining for one species that travel between the stars, perhaps for repairing the ship or possibly replace eroded radiation shields. But that would of cource be rather limited.

ljk4-1 said: My bets are on missionaries and/or there's a major galactic construction project going on.

Galactic construction project? You placed your bets on the arrival of the Vogon construction fleet?

[ljk4-1]

The suggestions put forth by Mr Richard Trigaux are mostly interesting possibilities, and I agree that the cost for interstellar flight -even for one extremely advanced civilization- would be so high that it possibly would take some kind of 'grand idea' of one kind or other before they would undertake and well open the wallet for the tremendous cost.

But I would be hard pressed to accept the idea of any kind of civilization that would mine minerals in one stellar system and then ship the metals over interstellar distances.
There might be need for mining for one species that travel between the stars, perhaps for repairing the ship or possibly replace eroded radiation shields. But that would of cource be rather limited.
Galactic construction project? You placed your bets on the arrival of the Vogon construction fleet? 

A Kardashev Type 2 or 3 civilization might have better and more urgent uses for the stars and other energy sources of the galaxy. Rearranging them to suit their needs might be on the list. Requiring materials for collecting that energy is another.

As for one reason to travel interstellar distances: Leaving a star system where the sun is going terminal or the planets are no longer habitable.

[Guest_Richard Trigaux_*]

But I would be hard pressed to accept the idea of any kind of civilization that would mine minerals in one stellar system and then ship the metals over interstellar distances.
There might be need for mining for one species that travel between the stars, perhaps for repairing the ship or possibly replace eroded radiation shields. But that would of cource be rather limited.

In the today paradigm as what intertellar travels are slow and difficult, there is no interest to send large objects, just seed ships (containing genetic codes) or automatons (automatic self-reproducing factories). So in this case there is no need of massive mining, and searching for mining traces on all our Kuyper belt objects (KBOs) may be a very tedious task, for an unprobable result. If there is a better way for interstellar travel, such as the Heim method (discussed elsewhere in this forum) there is no more need to halt en route.

By the way the better material for meteorite shields (against interstellar dust) is a thick multilayered honeycombed structure made of thin blades of carbon-carbon composite, eventually weighted with another material. Theses are precisely the most abundant materials in comets and KBOs (carbon + silicates). Water can be used to power fusion reactors.

I think it is realistic to envision fusion ships travelling at velocities of 1000km/s. At this speed they need about 300 years per light years, say 1200 years to reach Proxima Centauri. But if so, it is unrealistic to send manned ships at such a slow speed, unless there are very huge "world ships". Such huge ships could require massive mining of comets and KBOs.

[Guest_Myran_*]

Response to Richard Trigaux: I agree fully, my point was that interstellar flight would be a major task even for one really advanced spacfaring race/world.
So it was in response to you mentioning the 'need of mineral resources' that I intended to say that its quite unlikely but not impossible. And that any mining any aliens would do would rather be for secondary reasons.

There are some other materials suggested for a meteroite/radiation shield, one of them are to have a disk of beryllium flying a short distance ahead of a interstellar craft. But yes water could be used also, I think that was the idea in the book 'Songs from distant Earh' by Arthur C. Clarke and they indeed had to make a pitstop after their disk had been hit with something loosing most of its mass.

ljk4-1 said:

"As for one reason to travel interstellar distances: Leaving a star system where the sun is going terminal or the planets are no longer habitable."

Yes racial survival would of course put pressure on any race/species/entity, if any such develop (or even could) on a planet around one class A or F star they might be jumpstarted into becoming one interstellar society. That would of course also be something that would fit under my 'Grand idea' since spaceflight in that case would be a race for survival. Then we have the case of Homo Sapiens who are making their own planet inhabitable as we communicate here. I live in the arctic and havnt seen a normal winter for the last ten years. But im diverting from the subject and its too depressing to think about in any case.

[David]

Transmitting to One Million Worlds

SETI researchers have typically looked at any particular star system (at a given
frequency) for only a few minutes, at most. But what are the chances that an
alien signal has been sent our way just at the right moment to splash upon our
antennas during that brief interval?

Reading that article makes me think of two terms that might be added to the "Drake equation":

1) The percentage of technologically advanced civilizations that have an abiding interest in communicating with other intelligent species -- maybe the majority sentiment in the universe is solitary standoffishness (leave us alone!) or even paranoia (if we discover another intelligent species, they will kill and eat us!).

2) The bar for satisfaction of the desire to communicate with other intelligent species. What if it's enough to discover one intelligent species you can communicate, and you have no interest in digging up every single intelligent species in your galaxy? If our SETI program had turned up half-a-dozen intelligent species, wouldn't there be some sentiment that "okay, it's done its job, why bother continuing with it?" Maybe the 'lifetime' to be considered is not the lifetime of the civilization, but the length of time it takes before an extraterretrial SETI program actually turns up something -- at which point the beacons are turned off.

Of course, maybe that happens because they've aroused the awareness and wrath of the predatory interstellar Zorgon Empire, which brutally stamps out any civilization whose broadcasts interfere with their favourite soap operas...

[ljk4-1]

Sister Society Issues Call for Papers

For more information contact: Dr. H. Paul Shuch, Executive Director

(201) 641-1770, or email info @ setileague.org

For Immediate Release

LITTLE FERRY, NJ.., January 2006 -- The Society of Amateur Radio Astronomers (SARA), a SETI League Affiliate Society that represents several hundred amateur radio astronomers around the world, hereby solicits papers for presentation at its 2006 Annual Meeting, to be held June 18-21, 2006, at the National Radio Astronomy Observatory (NRAO), Green Bank WV. Papers on radio astronomy hardware, software, education, research strategies, and philosophy are welcome. Although the annual Green Bank meeting is, strictly speaking, a SARA event, this year SETI League members have been invited to participate.

H. Paul Shuch, The SETI League's volunteer executive director, also serves as SARA vice president. In that capacity, he is coordinating this joint technical meeting. SARA members, SETI League members, or supporters wishing to present a paper should email a letter of intent, including a proposed title and informal abstract or outline (not to exceed 100 words) to Dr. Shuch at vicepres @ radio-astronomy.org, no later than 1 March 2006. Be sure to include your full name, affiliation, postal address, and email address, and indicate your willingness to attend the conference to present your paper. Submitters will receive an email response, typically within one week, along with a request to proceed to the next stage, if the proposal is consistent with the planned program.

A formal Proceedings will be published in conjunction with this Meeting. Papers will be peer-reviewed by a panel of SARA members with appropriate professional expertise and academic credentials. First-draft manuscripts must be received no later than 1 April 2006, with feedback, acceptance, or rejection emails to be sent within two weeks thereafter. Upon final editing of accepted papers, camera-ready copy will be due not later than 1 May 2006. Due to printer's deadlines, manuscripts received after that deadline will not make it into the Proceedings. Instructions for preparation of final manuscripts will be emailed to the authors of all accepted papers.

At its 2006 gathering, SARA members will be celebrating the club's 25th Anniversary. SETI League members in particular are encouraged to participate in this landmark meeting by presenting their work for the benefit of the two sister societies. Further information about SARA can be found on their website, radio-astronomy.org.

Largely using radio telescopes and optical telescopes, SETI scientists seek to determine whether humankind is alone in the universe. Since Congress terminated NASA's SETI funding in 1993, The SETI League and other scientific groups have privatized the research. Amateur and professional scientists interested in participating in the search for intelligent alien life, and citizens wishing to help support it, should email join @ setileague.org, check the SETI League Web site at http://www.setileague.org/, send a fax to +1 (201) 641-1771, or contact The SETI League, Inc. membership hotline at +1 (800) TAU-SETI. Be sure to provide us with a postal address to which we will mail further information. The SETI League, Inc. is a membership-supported, non-profit [501©(3)], educational and scientific corporation dedicated to the scientific Search for Extra-Terrestrial Intelligence.

P.S. Tearsheets are always appreciated. Thank you.

-end-

--
H. Paul Shuch, Ph.D. Executive Director, The SETI League, Inc.
433 Liberty Street, PO Box 555, Little Ferry NJ 07643 USA
voice (201) 641-1770; fax (201) 641-1771; URL http://www.setileague.org
email work: n6tx@setileague.org; home: drseti@cal.berkeley.edu

"We Know We're Not Alone!"