Habitable Stars

General physics and astronomy discussions not directly related to Celestia
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Dollan
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Habitable Stars

Post #1by Dollan » 21.03.2004, 21:29

Hello folks...

I've been working on putting together a poor man's catalogue of habitable stars based on various criteria. My initial starting point was to utilize the Hipparcos-enhanced 150ly Chview file, and seperate all stars of spectral types F, G, and K. Stage Two was to whittle these 827 returns down by including only those stars that range from F7 V to K4 V, a standard for habitable stars. This brought the total down to 462 stars.

The current stage that I'm working on is eliminating all stars with luminosities either below 0.4xSol, or above 2.0 (in fact, I posted a question related to this in another section of this forum).

If anyone is interested, I can keep tabs on this little project in here. I realize that there are other resources available, not the least of which is the HabCat being used at SETI, but I found this a good distraction for my mind on some of my more hectic days, as well as a way to gain some first hand knowledge on some aspects of stellar mechanics.

So, anyone want me to keep tabs on the project in here?

...John...
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #2by marc » 21.03.2004, 21:56

Yes please.

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Post #3by Evil Dr Ganymede » 21.03.2004, 23:49

What criteria are you using though? I know tidelocked planets in close orbits around M V stars are considered to be habitable (see paper by Joshi et al.

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Post #4by Dollan » 22.03.2004, 00:06

I'm using several base parameters. I've mentioned the spectral types and luminosities. Next I will do a refinement for masses (although these tie into luminosity fairly well, so I don't expect much of a winnowing there). Following that will be a metallicity check; values below 0.4 (or is it 0.3? I can't recall off the top of my head) are thought to preclude the formation of rocky worlds, while those above 2.5 may actually inhibit it (this from Seth Shostak in an email sometime back; I'm hoping to contact him again for confirmation of that, since his reply was lost in my last great computer crash).

Two other points will revolve around stellar age, and finally orbital parameters if it is a multiple system. granted we don't know enough, but I'm going by the thought that if a planet can have a stable orbit, then that's okay (the question of whether or not planets could even form in such environments to begin with is just too difficult to pin a conclusive statement on).

As for the torch orbiting worlds... This is something I believe is possible, but for the time being I will treat those cases on a star-by-star basis. I believe, though, that this will open up everything from K5 V to M5 V or so. But there are so many such stars, it would take me forever to weed through them and decide which ones are suitable.

((did I mention I'm doing this for a sci fi project o mine, as well?))

...John...

Evil Dr Ganymede wrote:What criteria are you using though? I know tidelocked planets in close orbits around M V stars are considered to be habitable (see paper by Joshi et al.
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

Guest

Post #5by Guest » 22.03.2004, 14:25

Hi, John;

Did I ever send you my list of nearby sun-like stars?
I have no doubt that you have got all these anyway, but just in case-

Nearby Sun-like stars (all these stars are G class dwarfs)

Alpha Centauri A (Distance from Sol: 4.395 ly) (Luminosity 1.567 x Sol) (warning- binary system)
Tau Ceti 11.9 ly (Lum 0.463 x Sol) class
Eta Cassiopeiae 19.4149 ly, lum 1.287 x Sol
82 Eridani 19.77 ly, lum 0.632 x Sol
Delta Pavonis 19.92 ly, lum 1.231 x Sol
Xi Bootis 21.85 ly, lum1.440 x Sol (warning variable)
Beta Canum Venaticorum 27.3 ly, lum 1.203 x Sol (warning close orbiting binary pair)
61 Virginis 27.8 ly, lum 0.805 x Sol
Gliese 666 28.7 ly, lum 0.41 x Sol
Beta Comae Berenices 29.86 ly, lum 1.447 x Sol
Kappa Ceti 29.87 ly, lum 0.851 x Sol (possible close binary)
Gliese 442 30.14 ly, lum 0.815 x Sol
61 Ursae Majoris 31.12 ly lum 0.589 x Sol
Alpha Mensae 33.1 ly, lum 0.833 x Sol
Iota Persei 34.36 ly, lum 2.321 x Sol
Delta Trianguli 35.38 ly, lum 1.161 x Sol (close orbiting binary)
11 Leonis Minoris 36.46 ly, 0.746 x Sol
Gliese 534.1 37 ly, lum 0.5 x Sol
Lambda Serpentis 38.34 ly, lum 2.049 x Sol (close orbiting binary)
HR 6439 38 ly, lum 0.4 x Sol
Zeta 2 Reticuli 39.4ly lum 1.020 x Sol
Zeta 1 Reticuli 39.5 ly, lum 0.786 x Sol
Zeta Trianguli Australis 39.48 ly, lum1.399 x Sol (close orbiting binary)
85 Pegasi 40.5 ly, lum 0.64 x Sol (binary system)
55 Cancri 40.9 ly, lum 0.57 x Sol (several detected planets)
Gliese 302 41ly, lum 0.567 x Sol
Gliese 67 41.2 ly lum 1.45 x Sol (close orbiting binary)
Lambda Aurigae 41.2 ly, lum 1.83 x Sol
Gliese 95 41.35 ly, lum 0.406 x Sol
Gliese 620.1 42 ly, lum 1.01 x Sol +white dwarf companion?
Gliese 722 42.3 ly, lum 0.93 x Sol
58 Eridani 43.4 ly, lum 0.98 x Sol
HR 4489 43.46 ly, lum 0.4 x Sol
Gliese 853 44.39 ly, lum 1.127 x Sol
HR 8935 45 ly, lum 0.8 x Sol
18 Scorpii 45.7 ly, lum 1.08 x Sol
47 Ursae Majoris 45.9 ly, lum 1.679 x Sol (at least one planet)


As you know, I tend to think that every star will be able to support a population of some kind, although they might be extreme genetic tweaks , virtual entities or robots;
but these stars are most likely to have an earth-clone of some sort.

ooh look! GL 620.1 has got a white dwarf companion...

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Post #6by eburacum45 » 22.03.2004, 14:27

Logs in to claim the last post
(thinks- I'll have to check the luminosities of all these stars against the data in Celestia I suppose- there are often quite marked differences)

steve

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Post #7by Dollan » 22.03.2004, 15:24

Hey Steve...

Yeah, I'm certain all of those stars are in my current data base. Some of them will probably be winnowed out though. One of the final cutting points will deal with the orbits of any planets that have already been discovered, and will require a bit more research (47 Ursae Majoris is thought to be able to have a terrestrial world without disruption from the Jovians already in orbit).

And suns with white dwarfs... if they have a good seperation, and are old enough, I have to admit I'm a bit lost on what effect they would have on a Gaian world in orbit of the companion. Certainly there would be a marked effect on the biosphere, if it wasn't wiped out altogether.

...John...
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #8by brunetto_64 » 22.03.2004, 18:56

I have seen the joshi article, and I have found it interesting, may be to create a new kind of planet textures, with an iced emisphere ( that forever night) and the other emisphere with a eartlike circular region...this is work for Rass!!!!
8) 8) 8)
Brunetto

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Post #9by Dollan » 22.03.2004, 19:59

Hi Brunetto...

Although they haven't been added to the most recent version, I've thought a lot about different varieties of these type of worlds, which I have dubbed "Vesperian" worlds, for my Planetary Classification List.

One type would be quite Earth-like (Gaian), with the day and night sides kept at an optimum temperature thourgh atmospheric and oceanic heat transfer.

Another type would be with less water for heat transfer, making the dayside hotter, though habitable, with the nighside being much colder, perhaps like antarctica.

A third type would be the most inhospitable, with almost no surface water. The dayside would be hot and barren, while the nightside would be completely frozen, with only certain volcanic regions active to aid in atmospheric transfer. The only habitable zone would be near the terminator, and would probably be marked by strong winds as the atmosphere is being driven by the sun.

...John...
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #10by Dollan » 23.03.2004, 05:48

Well, I've powered through this list, eliminating those that did not
withstand the scrutiny of my luminosity elimination. Aside from those which were removed because they were below 0.4 or above 2.0, I found several doubles which I have also eliminated. apparently, the original Chview file has several errors in it.

So, of the previous 462 stars, there are now 207 remaining. Initially this
was a difficult project phase, as online resources are very hard to come by. I've resigned myself to accepting the fact that the resources that I *do* have will have various errors in them. As I mentioned, the original source file that I used had several stars which were doubled. But there is also the possibility of misidentification, mislabeling of stellar characteristics, distance errors, and so forth.

The sources that I have been using are varied, and I'll list them at the
very end of the project.

So, the next stage, Stage Four, will revolve around two attributes:
metallicity and age. I'm combining these two because these particular bits
of information are going to be *hell* to find, and in a lot of cases I'm
going to have to make my own judgments, based on stellar rotation and other parameters.

Wish me luck!

...John...
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #11by Evil Dr Ganymede » 23.03.2004, 05:59

Have you looked at Solstation's near star list? I have no idea who these people are, but they're really on the ball with their stellar data. You can often find metallicity and age data there.

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Post #12by Dollan » 23.03.2004, 06:12

Oh, absolutely! That is one of my main sources for data. I wish they'd expand their selection, but for what they have, it's really very good.

Actually, they are the same folks that gave us Chview; what a great program!

...John...

Evil Dr Ganymede wrote:Have you looked at Solstation's near star list? I have no idea who these people are, but they're really on the ball with their stellar data. You can often find metallicity and age data there.
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #13by brunetto_64 » 23.03.2004, 12:59

good site, Dollan...I will explore it better this afternoon...do you have the ssc files of planetary systems??? 8) 8)

Brunetto

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Post #14by Dollan » 23.03.2004, 17:50

Thanks, Brunetto!

Well, I'm just now getting Celestia going, trying to get used to it, all of that. I've actually had the program for a while, but I've only just been able to really mess with it.

My goal is to get all of the updated and med-to-high resolution maps for the solar system that are available (a slow process; I'm currently wading through Jestr's wonderful minor moon set, but with dial up it is a long process), then move on to the known extrasolar planet systems (of which D. Edwards, I think, is making some really remarkable textures for). Once that is done, I'll take a crash course into making my own systems, and input those into Celestia.

...John...

brunetto_64 wrote:good site, Dollan...I will explore it better this afternoon...do you have the ssc files of planetary systems??? 8) 8)

Brunetto
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #15by brunetto_64 » 23.03.2004, 17:52

Dollan what luck!!! but your site site is down??? :oops:
Bruno

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Post #16by brunetto_64 » 23.03.2004, 17:53

Dollan what luck!!! but your site is down??? :oops:
Bruno

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Post #17by Dollan » 23.03.2004, 18:14

hi Brunetto...

Yeah, my provider has been having another round of problems today, it seems. I've only recently begun getting my email again.

Keep checking back, they usually get things fixed within a few hours. I suppose this is the payment for the server having been stable for the past couple years: I've had similar problems several times in the last two months!

...John...

brunetto_64 wrote:Dollan what luck!!! but your site site is down??? :oops:
Bruno
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #18by brunetto_64 » 23.03.2004, 19:58

now it's up....
i'm surfing, and it's very good and accurate (the kentaurus system)
Bruno

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Post #19by Dollan » 23.03.2004, 20:04

That system, at least in general form, will be the template for the other systems. And, in fact, it is far from done; with luck, I'll be adding to it in the next few weeks, but really revisions will continue to be done for quite some time to come.

...John...

brunetto_64 wrote:now it's up....
i'm surfing, and it's very good and accurate (the kentaurus system)
Bruno
"To make an apple pie from scratch, you must first create the universe..."
--Carl Sagan

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Post #20by Evil Dr Ganymede » 23.03.2004, 20:37

John - what do you use to make the pictures of your planets? They're rather nice...


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