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Shortlist of Possible ET Addresses
An anonymous reader writes "Yahoo News is reporting that Astronomer Margaret Turnbull of the Carnegie Institution has released a 'top 10' list of potential inhabitable star systems. NASA is planning on using this top 10 list as the targets for their Terrestrial Planet Finder a 'system of two orbiting observatories scheduled for launch by 2020.'"
"...private philanthropists who pay for the bulk of their work may find out first when and if extraterrestrial life is discovered." I think that in the event of finding E.T life, SETI just might, you know, tell some other people as well.
While the chances of hearing from alien worlds is depressing small ("Rare Earth"), still the thought that a few private individuals will know first should give us pause. If there is more information in the detected signal than "hello there", who knows what could be learned? Markets may move in a big way (here's how antigravity works, immortality, existence of god, a big black hole is headed your way, etc.).
Then again if that's the only way we're gonna get these projects funded, perhaps these philanthropists should be rewarded for their risk taking.
The Terrestrial Planet Finder has been cancelled:2
http://www.spaceref.com/news/viewnews.html?id=109
So this list seems redundant. To bad, as it was NASA's most exciting project IMO.
But there is still ESA's Darwin, an essentially identical project, which is still scheduled for a 2015 launch as far as I am aware.
Now, is it just me, or does the idea that life may well need some abnormal event to kick-start it in conflict with that very idea?
Perhaps include *some* of these systems?
smash.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
This search for 'habstars' (habitable star systems) is really fascinating, and perhaps even practical in an offhanded way. What better way to inspire future astronomers and astrophysicists than to find some beautiful blue-green jewel like ours out there, even if we can't detect signs of intelligent life.
This would be a lot more motivating and captivating than scanning the heavens for shapes of creatures from mythology, which is no better than looking for pictures of Jesus or the Virgin Mary in a cheese sandwich.
Once we find something out there worth travelling to, then it would automatically spur thoughts of developing means to get there. Even if such dreams aren't possible due to the limits of known physics, it's still a noble and instinctive goal, like our grazing ancestors had in seeking greener pastures. Who knows where such thoughts might ultimatley lead?
Life on Earth 'unlikely to have emerged in volcanic springs'
13 Feb 2006
"The latest findings of experiments to re-create the conditions under which life could emerge from chemical reactions suggest that volcanic springs and marine hydrothermal events are unlikely to have provided the right environment, a leading researcher from the United States will tell an international meeting tomorrow (14 February 2006) at the Royal Society, the UK national academy of science."
In the alternative Plos ran an interestin article titled Jump-Starting a Cellular World: Investigating the Origin of Life, from Soup to Networks which touches on the front running theories on the origin of life.
"Academicians are more likely to share each other's toothbrush than each other's nomenclature."
Cohen
If memory serves me right ET was after a PHONE Number not his home address.
Jon - TheSpork
This "listing," "research," and "entire project" is all just for show...we've actually been travelling the galaxy to other habitable (and inhabited) planets from a secure facility inside Cheyenne Mountain--kinda surprised nobody mentioned that already! In fact, we've made friends with several other worlds and they joined our fight and helped us defeat a race of nasty snaky guys! Oh, and if anyone wielding a creepy glowing staff promises you candy for reading his book on Origin, run FAST. Sheesh...old news what?
"You want me to SIGN this thing?!"
Yeeeey, let's find some things to kill!
I think, therefore I am...I think.
"Any biochemists out there feel free to disagree and/or expound."
I'll take that one. In a liquid water environment it's difficult to see how you'd end up with a biochemistry that wasn't nucleic acid, protein, carbohydrate and fatty acid based. By observation life on earth seems to have explored just about every type of possible molecular structure that carbon/hydrogen/oxygen + other minor elements can produce and if there were some other useful biological molecule then it's difficult to imagine why it's not been 'discovered' and exploited already. That's not to say that the details won't differ - I'd have thought it virtual certain that a mix of different nucleic acids and amino acids would be used in different combinations with a different genetics etc etc, but I'd expect life to be grossly similar on similar planets, just differing radically in the details.
Outside that I'm very unconvinced by non-water or carbon based life. Silicon just doesn't form complex enough molecules so that's out. The next best bet seems to me to me ammonia based.
As Michael Griffin explains in Griffin Builds Hopes For Terrestrial Planet Finder And Hubble Rescue Missions.
The short reason is that the Crew Exploration Vehicle takes priority.
just 10? our intelligent designer has been busy!
NASA isn't looking for ET's phone numbers, they're confirming Gate addresses. It's only a matter of time before McGyver and team of Air Force officers are heading out into the galaxy to do battle with the Gua'uld!
She said NASA once had a policy of what to do, whom to call, and how to announce the news if someone detected a signal of intelligent life from space. "Today it is in fact a group of very generous philanthropists who will get the call before we get a press conference," Tarter said. They include Microsoft co-founder Paul Allen and Microsoft chief technology officer Nathan Myhrvold.
Crap. You can bet the aliens will end up with Windows on 90% of their desktops before they even hear of Linux.
Here or here, a very nice article on the project, "Margaret Turnbull and Jill Tarter have a new list, called HabCat: A Catalog of Nearby Habitable Stellar Systems." (2003) Interview included.
Interesting that starting with the Hipparcos catalog of 120,000 stars and skipping all with major problems for life ("cataclysmic, eruptive, pulsating, rotating, or X-ray stars", low metal content systems, rotating too fast or too much UV or bad size or composition), left 1 star in 6 still potential life bearers.
Wiki on HabCat and Turnbull. The Turnbull page has a link to a PDF, which is a very interesting scientific paper about how the list of habitable stars was made.
Wiki article on the Terrestrial Planet Finder, which uses Turnbull's list of 5000 candidates within a 100 light year radius. List of Top 100 candidates. Note 18 Scorpii at 46 light years is number 62 in the list, and 37 Geminorum is not listed.
The highest ranked 2 candidates in that list are just 4 ly away from Earth, at Rigil Kentaurus, and then Tau Ceti at 12 ly. There is one at 3 ly and some others at 19, 20, 24 ly too.
Allen Telescope Array
Turnbull's top 10 list includes 51 Pegasus, where in 1995 Swiss astronomers spotted the first planet outside our solar system, a Jupiter-like giant.
Others include 18 Sco in the Scorpio constellation, which is very similar to our own sun; epsilon Indi A, a star one-tenth as bright as the sun; and alpha Centauri B, part of the closest solar system to our own.
Send them a message containing the link: Click here to be removed from our mailing list..
It's rare that you're presented with a knob whose only two positions are Make History and Flee Your Glorious Destiny.
Lets do the math. Universe, ~13 billion years old. Earth, ~5 billion years old. Time to develop first sun-like stars perhaps 1 billion years. So there is a reasonable chance that there are (or were) Earth like planets up to 7 billion years older than Earth (at least around stars slightly smaller than the sun which age more slowly). There are some systems with younger Earths (*much* younger for those systems currently in the process of planetary formation). Lineweaver's group has worked on this and has concluded that ~70% of the Earth's in the galaxy are older than ours -- many of them by billions of years.
Based on this it is unlikely that either TPF or SETI (based on its current approaches) will discover "intelligent" life. The statistics dictate that you only have perhaps a 5000 (years) / 12,000,000,000 (years) chance (less than 1 in a million) of finding a planet which hosts "intelligent" life as we know it.
For those systems with terrestrial sized planets and those with water TPF is a reasonable effort -- it might manage to detect water and if lucky atmospheric composition that could hint at life. However pointing the SKA (or any other radiotelescopes) at the stars in the list provided are highly unlikely to be successful because they assume intelligent civilizations which are currently at (and remain at) our stage of development. (This changes the statistics to about 1 in a billion.)
The reasons for this are as follows... Whether you believe in steady state growth (Dyson's assumption in 1960), or exponential growth as "The Singularity" concept proposes the bottom line is that it seems very unlikely that a civilization would actively choose to remain at our state of development (i.e. zero growth for millions or billions of years). If you choose the steady state model the time to develop to a Dyson Shell is measured in a few hundred to a few thousand years. If you choose the singularity model then the time to develop a Matrioshka Brain (also here) is measured in decades. Once either of those states is reached the star goes "dark". So the star list is useless (to either the TPF mission or SETI) for identifying locations of intelligent civilizations with capabilities even slightly beyond our own.
Robert Bradbury
Notes:
For the above calculations I chose 5000 years as the longevity of humans with a reasonable level of technology development. One could limit it to smaller time frames (~100 years for radio or 40-50 years for lasers or rockets). TPF has a much greater chance of being successful than radio or optical SETI because it is working with a much larger time window. Water world longevities range from 100 million to many billion years if they restrict themselves to sun-like (
That's what I'm saying. I'd be highly suprised if alien life used precisely the same biochemistry, however I'd be equally suprised if it didn't use nucleic acids, amino/acid/proteins, sugars/polycarbohydrates and lipids. These grouping are too useful and easily available for them not to be used.
We can even reasonably be a bit more precise about it. With proteins of the 20 amino acids in prime use a good dozen of them could be expected to turn up in an alien biochemistry just because they're the simplest that do the job. With the carbohydrates many are also a dead certainty - glucose, fructose etc. and polymers like chitin are certain to be just as useful to alien biochemistry as they are to ours. On the lipid front, wll lipids are lipids and our biochemistry uses just about everyone going anyway so there's certain to be major overlap.
Nucleic acids are more interesting though. I'd lay a bet on RNA just because the ribonucelic acids tend to form easily in prebiotic conditions. DNA is more suspect, particularly as life here can get along without it just fine. Nevertheless it's the next simplest step up from RNA so may be favoured against other varients. Of course which nucelic acids are actually used is open to chance, although it's noticable that the ones we have are among the simplest.
Beyond these broad categories though indeed it gets more speculative. Even so, some assumptions seem probable. For example if there is RNA/DNA then a triplet genetic code is likely, because as has been observed, a doublet code doesn't give you enough combinations to work with (but there is evidence that our early genetic code was doublet and we evolved the triplet later) whereas a quad code would be inefficient needing 33% extra DNA to code and more error prone.
Other things that might also be expected to turn up. For example porphorins (the building block of haem, chlorophyll and many other useful molecules).
Unfortunatly I guess we'll never know, unless we strike lucky on Mars or Europa.
The submitter got it slightly wrong. First off, Margaret Turnbull's team came up with a list of 17,129 potentially habitable star systems in 2003, and the work she has done since has been to refine that list.
b le.shtml
What she announced yesterday were TWO "Top 5" lists. The first list includes the top 5 recommendations for a SETI search:
beta CVn
HD 10307
HD 211415
18 Sco
51 Pegasus
The second list includes the top 5 recommendations for the TPF to examine for Earth-like planets:
epsilon Indi A
epsilon Eridani
omicron2 Eridani
alpha Centauri B
tau Ceti
Why the difference? Well, the second list is of much closer stars, and much more likely to have planets that TPF can find and image. The first list has stars that are a bit farther away, but are, generally speaking, more like our Sun.
And here's a useful link:
http://www.aaas.org/news/releases/2006/0218habita
Bruce