IceAceTom

10/20/2010

3614

This is the first installment of a project that combines 3-D mapping of "Real Space" using AstroSynthesis with an experiment of mine in creating a science fiction universe. The AstroSyn .csv files are not just a simple data dump of a star catalog, but essentially a database, with a whole lot of stellar data, both given and calculated.

This is intended for fictional endeavors, not real-world use. I wanted plausibly realistic stellar data to build a universe upon, so while things like star names, distances and catalog numbers are the real ones, most of the calculated physical data was standardized into fixed ranges, and so strays from reality, though usually not too much. Simply put, each spectral class subdivision for main sequence dwarf stars (luminosity class "V", our Sun is a G2V star) was given a fixed mass range, and from that everything else was derived. Non-dwarf stars and oddballs were given a custom mass, usually similiar to the real one.

The AstroSyn Notes section for each star has been preloaded with loads of data, such as distance in ly, various catalog numbers, a standardized mass and luminosity, habitable zone distance (using a custom bolometric luminosity correction), the orbital period of a planet at that HZ and the tidal force exerted on that planet (so you can tell if you'll have a tidally-locked rotation period, though as with our own Mercury, that isn't always the case, and in fact you can set it up so even a habitable planet around a red dwarf isn't tidally locked, thus keeping one side from broiling and the other freezing).

Multiple star systems are also broken down and formatted for proper display in AstroSyn. Standard heliocentric galactic coordinates are also converted to AstroSyn's format (AstroSyn's X axisis the same as Xg, AstroSyn's Y axis is Zg, and AstroSyn's Z is the negative Yg).

There are two AstroSyn .csv files in the Space1 set. The first one includes almost all known stars out to 20 light years from Sol; brown dwarfs and the possible odd faint red dwarf aren't included.

The second file goes from 20 to 60 light years distance from Sol and includes all stars of absolute magnitude 9.50 and brighter; not included right now are all fainter red and white dwarfs that aren't already in the HabCat datset or are not components of a multiple-star system that has a member brighter thab abs. mag. 9.51. I will eventually make a separate file including these stars, but there are a large number of them and they just aren't that important to me for my purposes.

The source data used was David Nash's HYG Database and the HabCat dataset from Jill Tarter and Margaret Turnbull (see Winchell Chung's 3-D mapping discussion on his Project Rho website, www.projectrho.com/starmap.html, many thanks for that site). I then researched each star to gather data and weed out errors, using websites such as the Internet Stellar Database, SolStation's nearby star list, Atlas Of The Universe, ARICNS (the custodians of the Gliese Catalog), RECONS, and James Kaler's stars site at the Univ. of Illinois, along with using the Stellarium software.

Included in the .zip file are the two AstroSyn-format .csv files, along with the OpenOffice.org v.3.2.1 .ods spreadsheet files used to create them, they include all the formulas used so you can make your own dataset for your own fictional universe. I don't know if Excel is compatible with OpenOffice, but it is what I use, and OO is free. :-)

Oh, if you're not familiar with the HabCat, it's a subset of the Hipparcos catalog, with those stars out to a certain distance that are capable of hosting an advance sentient civilization, according to the authors' criteria. So these are stars that are old enough, single or are part of a wide binary, stable, and have a metal content ("metal" being all elements heavier than helium) high enough to have terrestial-type planets; there are lots of other factors involved too. Surprisingly, a large number of red dwarfs are included. Some of the stars in the HabCat already have had planets detected around them. So if you want to stay true to scientific accuracy when making habitable planets in a fictional universe, you'll only use the HabCat stars. I find that too limiting for my purposes, as I want a large number of the smaller F, all G and the larger K-type stars to potentially have earth-like planets, and never mind reality (like Alpha Centauri A *and* B; they aren't in the HabCat but I think it's just plausible enough to have a single habitable planet around each).

The HabCat stars in the data files are labelled as such in the "CAT TYPE" data column; the "PlusCat" stars are my "additions". Most of those stars make up my "Tier 1" in the data files. Stars labelled as "NHC" are "Non HabCat", being not members of the actual HabCat or my "PlusCat".

Some notes on the other data columns in the "Data" spreadsheets:

"Display Name" is what's used in AstroSyn's display; this is usually what the star is most known as or called, which could be a proper name (only if commonly used, obscure ones were ignored in favor of more familiar designations), Bayer letter, Flamsteed number or other primary catalog number (for example, many variable stars use their variable star catalog designation, like DX Cancri).

"Gliese" is the Gliese catalog number, includes the GJ numbers; I forgot why I put it here, probably because Gliese numbers are used a lot for many of the faint small stars.

"Spect2" is my derived spectral class, based on absolute magnitude and a fized mass range; with a few oddball stars I had to manually assign a spectral class in order to prevent going too far from reality.

"V" is visual magnitude, again usually taken from the HYG catalog.

"B-V" is the the B-V color value, thsi was also derived from fixed values, but it many cases I manually inserted a value that better matched reality.

"M" is absolute magnitude, this was calculated using the standard formula.

"Mass" is from my fixed mass range based on my derived spectral types; for Non-dwarf stars and other oddballs I again manually inserted a value that came close to reality.

"Dist LY" is the calculated distance from the Sun in light years, using the best and most precise parallaxes available; these were usually from the HYG catalog, but for the nearer stars I also used ones from the RECONS website.

"CAT TYPE" is the HabCat/PlusCat/NHC type described above; "MPL" means a multiple star.

"Tier" is what I use in my fictional universe to group stars according to value and desirability; Tier 1 is the best group, while red dwarfs are divided into two sub-groups under Tier 4. "N" in the Tier designation means a star not capable of hosting a habitable planet, i.e a "NHC" cat type and not one of the HabCat or my PlusCat stars.

"Tag" is a special identifier for some stars, like very old ones (OLD), UV Ceti-type variable stars (UVC), sub-dwarfs (SD), "superflares" (SF, some G-type dwarf stars are known to experience the occasional extremely massive solar flare, the kind that would sterilize the earth if our sun were to have one), and very close binaries (CB).

Following the "Tag" column are the alternate name and four different catalog numbers under which the star is known, if it's listed in them; they are the Hipparcos, HD (Henry Draper), HR (Hoffleit Bright Star) and BD (Bonner Durchmusterung) catalogs.

"LUM V" and "LUM B" are calculated visual and bolometric luminosties. The visual one used the standard formula; the bolometric one used my own custom bolometric correction value, based on my best estimates. The bolometric luminosity is important when dealing with K-type stars and red dwarfs, since as stars get smaller in mass they output a larger portion of their energy as infrared radiation--need to take it into account when ceating a planet around a small-mass star.

"RA" and "DEC" are right ascension and declination coordinates of the star in DMS format.

The next four data columns are the calculated bolometric habitable zone (it's the "center line" distance, where the solar equivaent energy output is found) in astronomical units (B HZ), the orbital period of a planet at that distance both in years and days(Per @ HZ), and the tidal force exerted on a planet at the HZ distance

The last three columns are the calculated standard heliocentric galactic coordinates. As noted above, these differ slightly from what AstroSyn uses; a simple conversion was done when the AstroSyn .csv file was created.