Celestia Forums

Hi. I registered here only a few minutes ago, because Celestia is the best astronomy program I've ever seen.

I've made an XLS file for adding new planets to Celestia, but I don't know how to put a link in this forum... you know, for download.

I think that the spreadsheet'll be useful for make new fictional planets around any star. Can somebody help?

the address where you can post it are:

Chris (the best master)
or
Bruckner (but he will going to wedding..)
or to his site : "http://bruckner.homelinux.net/celestia.html
or
D.Edwards
or
Rassilon

the address and the web pages are in the memberlist

or me.... brunetto_64@yahoo.it

thanks!!!

Bruno

...sorry for my english but I am italian....

I'm not anonymous!!!
Bruno

I am

Thanks for the information.

And one thing more... I am not anonymous (If I wasn't forget to login...)

Now I'm registered, I'll try to help and answer other questions.

Excuse me, I didn't want to criticize you, at times understands that the program doesn't take the name and
Then you appear anonymous…

I became angry me with myself…



Post scriptum
I have used the translator of word, excuse for my English…

Bruno

Anonymous wrote:Hi. I registered here only a few minutes ago, because Celestia is the best astronomy program I've ever seen.

I've made an XLS file for adding new planets to Celestia, but I don't know how to put a link in this forum... you know, for download.

I think that the spreadsheet'll be useful for make new fictional planets around any star. Can somebody help?

You can send it to me at claurel@shatters.net and I'll post it on the shatters.net. I plan on doing a bunch of other updates to the Celestia site this weekend, too.

--Chris

I'm working in a new version of the XLS file.

I want to include a system that can show you the temperature of a planet before placing it in the Celestia universe.

The formulae is 280,525 * (1-Albedo^0,25) / (Closest dist.+farthest dist.)^0,5

I'm trying to insert the proportion between the absolute magn. of a star and the temperature, but I can't manage to do this. Any help?

Astrobot

**** Luminosity of a star****

L = Area x sigma x T^4

Where:
L = total luminosity (in Watts)
A = total area of star = 4 x pi x R^2 (in m^2)
sigma = Stefan-Boltzmann constant = 5.6705 x 10^-8 W/(m^2 x K^4)
T = surfaced Temperature in Kelvins

L / Mabs relation:

L/Lsun = 2.512^(4.68-Mabs- B.C.)

L = total luminosity (in Watts)
Lsun = total luminosity of the sun (in Watts)
Mabs = absolute magnitude
B.C. = Bolometric correction (ask me for more information about this or ude my excel star generator to calculate)
http://usuarios.lycos.es/darktemplars/D ... stem01.xls

******************

****Temperature of a planet****

Eu (Energy per unit area in the orbit of the planet)

Eu = L / ( 4 x pi x D^2)

Eu = Energy per area unit in the planet's orbit (W/m^2)
L = luminosity of the star (W)
D = mean distance of the planet = U.A. x 150 x 10^9 (aprox) (m)

T basic:

Eu x pi x R^2 x ( 1 - albedo) = sigma x 4 x pi x R^2 x Tb^4

Tb = ( Eu x ( 1 - albedo ) / (sigma x 4 ) ) ^(1/4)

Eu = Energy per area unit in the planet's orbit (W/m^2)
albedo = albedo
sigma = Stefan-Boltzmann constant = 5.6705 x 10^-8 W/(m^2 x K^4)

T final:

Tf = Tb x greenhouse

greenhouse = 1 + 0.01 x P^0.5 + 0.1 x Pgr^0.5 + 0.1 x Wv

P = atmospheric pressure of the planet
Pgr = greenhouse gas presure
Wv = water vapor factor

Maybe these last formulae to calculate P Pgr and Wv are a bit hard for you ( I don't know) if you want to learn more, ask me please.

I am working in a Excel planet generator too, that will have all these formulaes and much more into account to generate worlds. I started last week so I only have the star generator ready. You can use it for the Luminosity/Mabs relation.

Here is a screenshot:



You can download it directly here:

http://usuarios.lycos.es/darktemplars/D ... stem01.xls

it wil be impemented in the next days

The formulae:
280,525 * (1-Albedo^0,25) / (Closest dist.+farthest dist.)^0,5

have no very much sense for me, please how have you calculate it?

Celestia takes into account the albedo factor but no the greenhouse effect that in some cases is much greater than the albedo influence.

It's very simple.

First, I created an example SSC file with one planet.
Then I put it in diferent distances and take note of temperature (about eight times), and the same with albedo.

I've used Excel graphics to extract the two formulaes, and then combine.

The formulae works always, while the star is the sun.

The empirical system is not the better one and Celestia have a lighter temperature desviation, about 2 C in earth and maybe more in other planets.

If you want to make a real calculus I suggest you that try to use real formulaes not empirical ones. Your formulae is mainly right but to be congruent your formulae:

280,525 * (1-Albedo^0,25) / (Closest dist.+farthest dist.)^0,5

I think must be:

280,525 * (1-Albedo)^0.25 / (Closest dist.+farthest dist.)^0,5

The first number 280.525 or 280,525 ( remember to use only one type of decimal separation ) is the Sun temperature constant for your empirical form. It is variable for other kind of stars.

If you want and have a messenger hotmail account talk me directly in:

j_omar7@hotmail.com

I will try to help you more in english or spanish what you want

Saludos desde Madrid Astrobot

Thanks for the advice!

Now, I'll try to perform my worksheet... but it can only work in Celestia.

And thanks for all the formulae, also I'll try to make a similar file for calculing data acording to the real universe, for personal use.

I don't have a messenger acount, but if you want to know, my e-mail is A020686@SUPERCABLE.ES

I'd like to see your planet generator and your star generator is pretty good.

Un saludo de Sevilla!

At last the final Star System generator is completed, with it you can be able to generate random star and double close star systems. It had a lot of bugs (especially with the cooling if brown and white dwarves)

You can use this one to get useful information about the stars in Celestia, specially the mass, life zone... etc.

Here are some screenshots:





You can download directly the Star generator here:

http://usuarios.lycos.es/darktemplars/D ... %20Gen.xls

Wait few weeks for the planet generator...


This is the first step, now all is ready to the Planet generator. This one will allow all of you to make real planetary systems very easy. It will have:

Orbital data
Tidal lock
Axial tilt
Seasons
Lunar objects
system disruption
geopysical data
tectonic activity
magnetic fields
hydrosphere reference
atmospheric composition
albedo
surface pressure
surface real greenhouse temperature
.... and much more

Does the above output an stc file? If not...you should ...Should be possible using VB for Spreadsheets....

Yes, the star generator is a good tool, and if it could make STC files, it'll be a wonderful tool.

But I think it'll be dificult, and the file is good now.

I've sent my file also, it's finished. I sent it to Chris and Bruckner.

Yes it would be very time consuming indeed...Do you know any programming?

Well I hope this will answer all your questions about the Star Generator.

First One the Star generator is only a firts step to make real planetary systems for Celestia. It could be used fow make new star but the problem is about the coordinates. There is not an "easy" way to generate random galactic coordinates for a Star there are too much variables involved.

- The Shape of the galaxy
- The star distribution (blue in spiral arms red un halo and bulge)
- Star Cluster
- Far binary systems
- star associations
- etc

The problem to convert the galactic coordinates to center earth coordinates (distance Ra and Dec that Celestia uses) is easy; the shape of the galaxy can be randomized but the other problems are very hard. If anybody could suggest anything...

Second One. Yes the final idea is that the excel could give almost directly the .scc file for Celestia. This is not a hard work, only let the last page to rearrange the all the system planets and moons parameters at Celestia "way" to work directly; I had tested this one with samples and works fine.

Third and last one. The planet generator are building without big problems by the moment. It can calculate now:

Distance
System zone
Removed orbits
Planet type
Radius
Density
Mass
Surface gravity
Escape velocity
Orbital Period
Eccentricity
Closest Aproach
Further separation
Tidaly Locked ?
Axial Tilt
Rotational Period
Solar Day

But there are much more:

Moons
Composition
Tectonic Activity
Asteroids Belt Type
Base Temperature
Hydrosphere
Water Vapor
Atmospheric Composition
Atmospheric Pressure
Oxygen Percentage
Scale Height
Pressure at Sea Level
Atmospheric Mass
Albedo
Greenhouse effect
Surface temperature
Seasons
... more

And of course test and test until it works with no problems and implement the celestia file output.

Looks good Templar...I think it covers all the bases...One I would like to see is a star generator that could output a global star cluster of 100-10,000 stars into a stc file...Nothing too complicated more random than anything...for the galactic center of a galaxy....

Thing is currently the stars are limited to 16,000 ly before they disappear so this is something that could be made now and by the time chris fixes that...it could then be used...maybe I will write it if no one else wants too

Yes, it must be interesting including a random star cluster in Celestia, and with respective random planets.

Visiting all will take many hours.