Curated data-sets for TRIPS

Contents

• Background

• Known Issues in provided datasets

• Why there are two different types of data files?

• Data Restrictions

• Special Values

• Data Dictionary

Background

The basic TRIPS data sets are derived from the Gaia Dr2 data. We are aware that the Gaia team has released a preliminary version of Data release 3. We are currently ignoring that.

We chose 270 light years as a reasonable radius for our base data set. That should be able to be loaded and fairly responsive on any computer built in the last fifteen years running any version of windows from Window 7 service pack 1 to the present.

Known Issues in provided datasets

The datasets provide only stars and star systems. There are no nebula listed, nor any other non-star based object such as gas clouds, dust clouds etc.

Not all the data in GaiaDr2 within 270ly was included in the TRIPS data set. Specifically we ignored objects that had poor astrographic certainty or poor parallax certainty. Generally, that means we skipped very faint objects and objects with few detections that were likely transients.

In addition, there are well-known objects that have very poor Gaia data because the sensors in the satellite, which are designed to measure very dim objects, are dazzled by very bright objects and give poor measurements of them.

There are other issues. In the discussion of Dr2 the Gaia team points out that they should be able to make a 1 to 1 match between Gaia objects and Hipparchos objects. They were not able to do that. No one knows if the problem is on the Gaia side or the Hipparchos side, nor why. We did the best we could choosing what to include.

We took full use of Gaia’s cross-matches they published with pre-existing catalogs and assume that if they found a cross match, the object is real and should be included.

Once that filtering and cross-matching was done, we took full use of the Simbad system to gather astrometric data Gaia’s sensors couldn’t produce such as UBVY magnitudes, spectral class and luminosity, stellar type (dwarf, giant, etc.), temperature and so on. Objects that aren’t found in Simbad, and data which is not available in catalogs like Hipparchos, Tycho, 2MASS, WISE, etc simply have those fields unpopulated.

Even for objects in Simbad some lack information we regard as critical like spectral class. Specifically 181,700 of the 216,422 objects we have included in the data set lack a spectral class at all. We will continue over time to let our update scripts retrieve any new data published about those stars but frankly, we hold out little hope for timely results.

Additionally, there are binary or multiple star systems included in those 216,422 which are not broken apart into their components. There may be data on the individual stars but our existing data sets may not list them seperately. The current version of the program doesn’t have a method for listing a multi-object system and then drilling down to its individual components, be that planets or stars. We’ve noted binary and multiple systems but the drill-down is for some future version. In the mean time somestar systems are detailed with ‘xxxxxxx A’ and ‘xxxxxxx B’ etc. Over the course of time that will be expanded, but for now it’s hit and miss.

Why there are two different types of data files

In the downloadable data sets you will find two types of files. One set are named Trips-Gaia-raw… and the other are named Trips-normal-names. Why, and what are they?

When creating the datasets in order to standardize things as much as possible we made the decision that in our “master” data releases we would simply leave blank fields we didn’t have data for, even if we could guess well. For example; knowing the UBVYI magnitudes of a star and its distance we can guess at temperature and luminosity. In the base data set, we didn’t do that.

Also, where an object exists in the Simbad system, we chose to use to use the Simbad object name for the object in all cases. For example the star “Alpha Centauri” has the name “* alf Cen” in the Simbad system. Many common well known objects have these somewhat cryptic identifiers as a result. For example a variable star with the Flamsteed catalog ID of Iota Eridani would have the id of “V* iot Eri” from Simbad. During the development of the system this was very useful. For day-to-day use, not so much. These data files are called TRIPS-Gaia-raw files.

For “everyday” use, espectially for use by the SF community, we made some different decisions. For the SF versions of the datasets we replace the displayname as follows:

• Removed prefixes from star identifiers, specifially removing *, **, V*, V**, and “NAME” from the display name of the stars.

• Expanded all constellation names to full spelled out versions. “Eri” becomes “Eridani”. Most of the time we use the genative version of the name thus “Alpha Canis Majoris” rather than “Alpha Canis Major”. This is still somewhat inconsistent, but we’re working on it. We will happly have discussions about it.

• Expanded all greek letter abbreviations in Flamsteed ids to fully spelled out versions of the letter name. Thus Alpha not alf. In no case do we use a greek character.

• Replaced the displayname entirely when a “common name” exists thus Altair not “alf Aql” nor “Alpha Aquilae”

Also, for “everyday” use in the SF community we have created “guessed at” stellar classes where there was any data to make a guessed at class from. For the tens of thousands of stars we known none of the critical information about, in each 10ly radius from Sol, we created an entirely fictional spectral class and luminosity based on the actual probability of any such object existing.

Data Restrictions

All the data in the curated datasets are from public domain sources. You are free to modify the datasets or to create your own.

Special Values

The program was written at the request of Chuck Gannon to replace the old ChView program he used for astrographics to aid in writing his Terran Republic or Caineverse stories. So, Chuck got to pre-set some things. Among others, the query system in the program “knows” the names of his species in the Cainverse: Terran, Dornani, Ktor, Arat Kur, Hkg’Rkh, and Slassriithi. Similarly, he specified pre-chosen values for world-types, fuel-types, products, etc. If you want to use the pre-configured “Selectg stars from dataset” dialog you will have to use those values in the fields for Polity, Fuel, Products, etc.

As of version 0.67 you have to just type those names. In the future plans for the system a screen to customise user values is planned. At that time you will be able to modify the presets and the presets will generate pick-lists (combo-boxes) for the fields used for fictional data. For now though, you have to just type them, and live with Chuck’s choices.

Data Dictionary

The program is somewhat picky about the values in certain fields. The table below names each field, describes it, and says if a value is required. When preparing datasets to be imported all columns are required even if blank and they must be in the order shown below.