Stellar Mapping


Stellar Mapping title

Latest update: 25th May 2013

SECTION 0: INTRODUCTION

The aim of this project is to show the locations of the stars around Sol as accurately as possible. This dataset is aimed at anyone interested in astronomy or who is interested in adding nearby stars to their own RPG or sci-fi/Traveller universes – the raw data is easily adaptable to any sci-fi setting or RPG. Every effort has been made to make the data as simple to interpret as possible, though FTL routes have not been calculated here.

The stellar data is visualised using Astrosynthesis 3.0, published by NBOS, which is available for $35 from DrivethruRPG and RPGNow (I strongly recommend buying it if you’re interested in this sort of thing – which presumably you are, since you’re reading this – it’s an excellent 3D visualisation tool!)

Section 1 describes the techniques used to convert existing astronomical data into a more usable form. An Excel file is also provided for users to convert from RA/DEC to Galactic Coordinates and back again.

Section 2 presents the star data. Several star datasets and catalogues are provided (each with its own advantages and disadvantages) that include stars up to 300 lightyears from Sol. The data is presented in CSV (comma separated variable) format, which can be read into both Excel and Astrosynthesis. AstroDB files are not included here since they can be easily generated using Astrosynthesis after importing this data.

Section 3 provides some advice and ideas for combining and presenting the data in Astrosynthesis.

Section 4 presents links to additional articles that expand on the Stellar Mapping page!

Section 5 lists any updates to the data presented on this page. (e.g. stars added to datasets that had been omitted for various reasons).


 

SECTION 1: DATA PROCESSING

Co-ordinate Converter

The Excel 2007 coordinate_converter spreadsheet allows you to convert between J2000.0 Right Ascension/Declination and Galactic Latitude/Longitude (both ways) for a single star, and also provides X/Y/Z co-ordinates for the star if its parallax is known. All of these data can be accessed from Vizier and other sources. The spreadsheet requires the Right Ascension and Declination (in hr/min/sec and deg/min/sec respectively, both in J2000.00 epoch) and the J2000.00 trigonometric parallax values (in arcseconds). (Thanks to Veeger, PraedSt, and Grant Hutchison from BAUTforum, and Spaceman Spiff and Selden from the Celestia forums for all their help with figuring out the conversions).

Download: Coordinate_converter: J2000.0 equatorial co-ordinates <--> galactic co-ordinates conversion spreadsheet

If you want to convert lists of stars from equatorial to galactic co-ordinates and galactic XYZ, you can use the bulk_converter Excel 2007 spreadsheet – just copy/paste the RA/Dec or alpha/delta (decimal coordinates) and copy the formulae in the tables. A sample star is shown, and the Explanation tab explains the columns. This spreadsheet will also convert to Astrosynthesis X, Y and Z co-ordinates.

Download: Bulk_Converter: converts lists of stars from J2000.0 equatorial to galactic co-ordinates

Note that J2000 equatorial co-ordinates must be entered into the spreadsheets. This conversion should also work without modification for J1991.25 equatorial co-ordinates from the Hipparcos database, but it’s best to use J2000.0 just in case. J2000.0 co-ordinates can be downloaded from Vizier using the “Compute” options in the search forms there. The spreadsheets will not produce accurate results for data from earlier epochs (e.g. 1950.00) – this is due to inaccuracies in the older data, along with precession of the star co-ordinates since that epoch.

A note on co-ordinate systems

Right Ascension and Declination are equatorial co-ordinates, and can be imagined as the Earth’s latitude and longitude projected into the celestial sphere. RA (Right Ascension) is measured in hours/minutes/seconds, and Dec measured in degrees. The RA zero meridian is the “first point of Aries”, where the sun crosses the celestial equator in March. A Dec of 0° would be at the celestial equator, defined as the projection of the earth’s equator into the celestial sphere. Polaris is at a Declination of around +89°, making it the north pole star.

Since these definitions are specific to Earth, it doesn’t make much sense to use them to mark star locations. Instead, galactic co-ordinates are used – this co-ordinate system is centred on Sol, with 0° Galactic longitude pointing towards the galactic core (Coreward). Longitude is measured anticlockwise from this line (90° is Spinward, 180° is Rimward, 270° is Trailing). Since Sol is actually located about 67 lightyears above galactic plane, the Galactic Equator is the plane parallel to the galactic plane with Sol at its origin. Galactic latitude is also measured from Sol, with positive (Galactic North) latitudes being above the galactic plane, and negative (South) latitudes being below the galactic plane. (see http://en.wikipedia.org/wiki/Galactic_coordinate_system for more information).

Conversion from Galactic XYZ to Astrosynthesis XYZ

The coordinate_converter and bulk_converter spreadsheets assume that the +X axis is the Coreward direction (directly towards the galactic core, at 0° Galactic Longitude), the +Y axis is Spinward (the direction of galactic rotation, at 90° Galactic Longitude), and the +Z axis is “up” towards Galactic North. These Galactic XYZ co-ordinates can be used without modification for most purposes.

However, Astrosynthesis uses a different XYZ orientation, so the Galactic XYZ co-ordinates must be converted to that reference frame before being used there. In Astrosynthesis, +X is the Trailing direction (opposite to the direction of galactic rotation, at 270° Galactic Longitude), +Y is “up” towards Galactic North, and +Z is the Rimward direction (directly opposite the galactic core, at 180° Galactic Longitude). Thus:

 Galactic to Astrosynthesis   Astrosynthesis to Galactic 
 Galactic Y * -1 = Astrosynthesis X   Astrosynthesis Z * -1 = Galactic X 
 Galactic Z = Astrosynthesis Y   Astrosynthesis X * -1 = Galactic Y 
 Galactic X * -1 = Astrosynthesis Z   Astrosynthesis Y = Galactic Z 

Note that the bulk_converter spreadsheet includes this calculation – use the AS X, AS Y, and AS Z columns if importing the data from there into Astrosynthesis!

Because of this re-orientation, the Astrosynthesis XYZ files must only be used for importing the data into Astrosynthesis. The Galactic XYZ files should be used for any other purpose.


 

SECTION 2: STELLAR DATASETS

The Stellar Mapping datasets presented here were created using the Conversion spreadsheets described in Section 1. Equatorial RA/Dec co-ordinates for each star were converted to corresponding alpha/delta (decimal degree) values (RA/Dec were provided as decimal values in the New Reduction) and then into galactic co-ordinates – trigonometric parallax values for the stars were also taken, and converted from milliarcseconds to lightyears and parsecs (the correct distances are assumed to be in the centre of the error bars). The galactic co-ordinates and parallaxes were then converted into orthogonal Galactic X/Y/Z co-ordinates.

Two versions of the CSV files are provided for each dataset – one in Galactic XYZ (that can be used for any purpose except for Astrosynthesis), the other in Astrosynthesis XYZ (ONLY for use in the Astrosynthesis program – do not use this for any other purpose!). The files have been compressed into zip files that contain the CSV file and an explanatory text file. The larger catalogues contain a CSV of the complete dataset as well as smaller CSV files containing smaller subsets of the dataset for convenience. Make sure you download the correct version for your purposes!

 

Accurate Datasets

The RECONS, DENSE, CTIOPI, and EXTENDED HIPPARCOS datasets should be considered “accurate”, in the sense that they contain the most up-to-date stellar data that I can find. It should be noted that there are certainly other stars within 300 ly of Sol that are not included within them – some have not been discovered and catalogued yet, while others may be found in other stellar databases that I have not tracked down and included here. The datasets presented here should NOT be used for scientific purposes as they have been edited and have not been peer-reviewed – if you are doing scientific research then use the original material from the source datasets!

The RECONS, DENSE, and CTIOPI datasets can now be downloaded in a single zip file that includes separate RECONS, DENSE, and CTIOPI CSV files in either Astrosynthesis XYZ or Galactic XYZ format. These three datasets should be used with the Hipparcos dataset, and include no overlaps or duplicates (as far as I can tell). This zip file can be downloaded after the CTIOPI description below.

 

RECONS: The RECONS list of the 100 nearest star systems is currently the most accurate list of stars near Sol. This list represents the current state of our knowledge of stellar and substellar objects around Sol, and is updated on a yearly basis. The most distant star system on the RECONS list (LP 771-095) is at a distance of 22.7 lightyears. The RECONS data presented here includes accurate spectral types and mass, and also lists companions to multiple stars.
Updated 5th Feb 2012: HIP 84709 (Gliese 667) has been added to the RECONS CSV files! See Section 5 for details.

Source:http://www.recons.org/TOP100.posted.htm
Number of star systems: 109
Distance range: 0.00 – 22.7 ly from Sol.
Accuracy: positional, mass, spectral and companion data are accurate. Radius and Luminosity data are not included (last update – Jan 2012).

 

DENSE: The DENSE project is located on the RECONS website, and is a separate database that includes accurate locations for 136 white dwarfs within 25pc of Sol (some of these are members of multiple systems too). However, this is NOT the original dataset – it has been edited for typo corrections in the original data, and also has had alternative star names added (where known). Spectral types have been added from the White Dwarf Catalogue at http://www.astronomy.villanova.edu/WDCatalog/index.html.

Some of the entries from the original DENSE list have been removed since there is some overlap in the CTIOPI dataset – full details of the edits can be found in the “CTIOPI-DENSE merging details” section in the readme file in the zip file. Note that duplicates that are also present in RECONS have been removed from the DENSE list presented here.

Source: http://www.denseproject.com/25pc/ (edited).
Number of star systems: 106.
Distance range: 22.7 – 81.5 ly from Sol.
Accuracy: Positional and spectral type data are accurate, but mass, luminosity and radius are generic. Companion data is not included.

 

CTIOPI: CTIOPI (Cerro Tololo Interamerican Observatory Parallax Investigation) is another dataset from the RECONS group – its purpose is to discover red, white, and brown dwarfs that are within 25pc of Sol.

It is important to note that the CTIOPI dataset included here is NOT identical to the original CTIOPI dataset on the RECONS website – there is some overlap between the CTIOPI dataset and the DENSE white dwarf dataset, which means that both datasets have been edited to remove duplicates. Full details of these edits can be found in the “CTIOPI-DENSE merging details” section in the readme.txt in the zip file. Note that all CTIOPI entries within 22.7 lightyears have been removed to avoid overlap with RECONS.

Updated: 24th March 2010 – Separated multiple-star systems in CTIOPI have now been re-combined as single systems. If the A/B/C components of multiple-star systems were separated by several lightyears in the original data (due to parallax inconsistencies) then they have now been combined as Multiple systems at the location of the A star (this is assumed to be at the correct distance for the system). Some stars were originally listed as solitary “A” components without any corresponding B components listed at all – these have been left as single stars, but it can be assumed that they are actually multiple stars with the other components at the same location as the A star. Also, Gliese 2130 ABC has been added to the CTIOPI dataset.

Source: http://www.recons.org/publishedpi (edited).
Number of star systems: 165
Distance range: 22.7 – 827.8 ly from Sol (most are within 100 ly).
Accuracy: Positional and spectral type data are accurate, but mass, Luminosity, and radius are generic. Multiple systems are listed where known.

 

EXTENDED HIPPARCOS: The Hipparcos dataset is currently the most accurate dataset for stars beyond the extent of RECONS, but does not include the dimmest stars. The Extended Hipparcos (HIPX) dataset is the latest version, published in 2012 by Anderson & Francis. HIPX includes spectral types, luminosities and other data from various datasets and combines them with position and parallax data from the previous New Reduction Hipparcos (van Leeuwen, 2007) and original Hipparcos datasets. While most of the HIPX parallax data is taken from the New Reduction, some of the multiple star system parallaxes were revealed to be inaccurate – in these cases, the star system’s parallax was replaced by data from the Original Hipparcos dataset. This means that there are differences between HIPX and the New Reduction dataset that was presented here previously. The Extended Hipparcos dataset presented here has been clipped at 300 ly from Sol.

Updated: 24th March 2010 – Separated multiple-star systems in HIPX have now been re-combined as single systems. If the A/B/C components of multiple-star systems were separated by several lightyears in the original data (due to parallax inconsistencies) then they have now been combined as Multiple systems at the location of the A star (this is assumed to be at the correct distance for the system). Some stars were originally listed as solitary “A” components without any corresponding B components listed at all – these have been left as single stars, but it can be assumed that they are actually multiple stars with the other components at the same location as the A star.

Source: http://vizier.u-strasbg.fr/viz-bin/VizieR-3?-source=+V/137A/XHIP.
Number of star systems: 20,089
Distance range: 22.8 – 300 lightyears from Sol.
Accuracy: Positional data are accurate, spectral/physical data are accurate where presented, mass is generic. Multiple systems are listed where known.

 

LDWARF: The LDwarf dataset is a list of brown dwarfs that have parallaxes associated with them, taken from the IPAC Brown Dwarf Archives – this dataset was last updated on 14 Feb 2011. It is not a complete list of all known brown dwarfs – hundreds more are known, but distances for the others cannot be determined because parallax data does not exist for those objects.

While some of the distances presented in this dataset are derived from trigonometric parallaxes, others are derived instead from (spectro)photometric parallaxes. Trigonometric parallaxes are derived geometrically and are generally more accurate than photometric parallaxes, which are derived purely from spectral and luminosity data. “Photometric parallaxes” are techically not really “parallaxes” at all – instead the spectral type of the object is checked against luminosity models to get an estimate of its luminosity, which is used along with the observed visual/IR magnitude to calculate the distance of the object. Unfortunately this method is not very precise, which means that some of the photometric parallaxes for these objects have very large error bars – but this is the best data that is currently available.

NOTE: One system – SDSS J141-134 (#25004 on the list) – is listed in the original data as having a parallax of 127 +/- 27 mas. This places it almost in the right location to create a 7.7 ly link between Xi Bootis and CE Bootis, which would be very useful in the 2300AD setting. Since the error bar is very large, I have changed its parallax to 122 mas on this list (still within the error bar, which does allow it to connect those two stars) – this number is shown in the mass column, listed in arcseconds. The original (127 mas) data for this system is listed in the text file in the LDwarf.zip file.

It should also be noted that two Brown Dwarfs (UGPS J072227.51-054031.2 and DENIS J081730.0-615520) are located within the RECONS sphere. These are not listed in the RECONS data, but are retained here since their parallaxes indicate that they are within 22.8 lightyears of Sol (even given their large error bars). They do not make a significant difference to the 2300AD route distribution.

Some of the Brown Dwarfs in this list are members of multiple systems that are listed in other datasets presented on this site. These are listed as complete multiple star systems on this list (the other components are duplicated here using the original data) – the datasets should merge seamlessly when combined (the ID numbers are preserved in both lists) but some components may be duplicated – this should not create problems since they will have the same name and position.

Updated: 25th May 2013: The LDWARF Galactic XYZ file contained incorrect data! The Z-coordinate values in the old file were all wrong (they were incorrectly calculated, and were actually the +X coordinates). I’ve replaced the Galactic XYZ file with the corrected data, and it is available for download in the LDWARF download section – thanks to Dr Charles Gannon for getting me to look at it again! (The Astrosynthesis XYZ file was fine, so that doesn’t need to be replaced).

Source: http://ldwarf.ipac.caltech.edu/archive/version5/viewlist.php?table=parallax&format=text.
Number of star systems: 79
Distance range: 0 – 331 lightyears from Sol (most are within 100 ly).
Accuracy: Positional data are accurate (with the exception of one system – see above), spectral/physical data are accurate where presented, mass is generic. Multiple systems are listed where known.

 

Other datasets

These datasets are either subsets of the datasets listed above, or are presented here for historical purposes.
The Yale and Gliese 3 Datasets have now been moved to their own blog post to keep them separate from the more accurate data presented here.

The Pleiades Corridor: The creation of this custom dataset is described in my “How to make a Stellar Database” blog article. It includes all Hipparcos stars in a corridor between Sol and the Pleiades star cluster, extending out to 500 ly from Sol. If you’re familiar with the 2300AD RPG, this should contain the approximate path that the Bayern took to reach the Pleiades star cluster! This has now been updated to use Extended Hipparcos data.

Source: Extended Hipparcos Catalogue.
Number of star systems: 144
Distance range: 22.8 – 500 ly, corridor of stars includes the Pleiades star cluster and goes slightly beyond it.
Accuracy: Positional data are accurate (extracted from Extended Hipparcos dataset), spectral/physical data is accurate where known. Mass is generic and luminosity/radius is not provided. All stars are listed as single stars.

 

Further Stars: The “Further Stars” dataset is a custom list based on the stars described at Solstation.com. Most stars are within 300ly of Sol, but some further bright stars of interest are also presented (the furthest star listed is Alnilam (epsilon Orionis), at a distance of just under 1977 lightyears). Note that this dataset has not been updated to Extended Hipparcos yet! I will be updating it to HIPX at a later date, but it does contain duplicate stars in different positions and should be considered to be less accurate than the other datasets!

Source: New Reduction Hipparcos Catalogue.
Number of star systems: 194
Distance range: 22.8 – 2000 ly (most stars within 300ly)
Accuracy: Positional data are accurate (derived from New Reduction HIPPARCOS data). Spectral Type, Mass, Radius, and Luminosity are generally accurate, derived from a combination of wikipedia, Celestia, and James Kaler’s Stars site. It should also be noted that all the Further Stars are listed as single stars, but many are actually multiple star systems (only the A component is listed here) – users are encouraged to research specific stars further if they need more information about them.

 


 

SECTION 3: USING THE DATASETS

Importing the data into Astrosynthesis

These datasets can be easily imported into Astrosynthesis 3.0. Make sure you download the Astrosynthesis XYZ version of the dataset and unzip the CSVs into a folder. Then start Astrosynthesis (this will create an empty sector), and go to the File/Import menu and select “Import CSV data”. Press the “Browse” button and point it to the file you want to import, and make sure “add to existing sector data” is selected. Start with the RECONS dataset, and then individually import any other datasets you want to include if you are combining them. Once you’ve imported all the datasets that you want to use, save it as a new AstroDB database file by going to the File/Save As menu.

You’ll end up with something like this:

RECONS-coreward

RECONS dataset, looking towards Sol and the galactic core.

RECONS-top

RECONS dataset, looking down at Sol from the Galactic North Pole.

Combining the datasets

If your primary concern is accuracy, you must combine the RECONS, edited DENSE, edited CTIOPI, and LDwarf datasets with the Extended Hipparcos dataset only. This gives the most complete census of known stars with accurate positional data. There are no overlaps or duplicates between these datasets. The Pleiades Corridor dataset may also be combined with these (there will be duplicates with the HIP dataset, but this should not matter since the data are identical).

The other datasets are presented here as curiosities:

The Further Stars dataset is a subset of New Reduction Hipparcos, but includes only a relatively small selection of stars (some of which are beyond 300 ly). It should not be combined with the Yale or Gliese3 datasets. Care should be taken if combining it with the other datasets, since some of the star positions may have been updated in the Extended Hipparcos datasets and some of the stars between 22.8 and 300 ly have been duplicated (in different positions). This dataset will be updated to HIPX at a later date.

The Extended Hipparcos, Yale and Gliese3 datasets should never be combined with eachother, as they will contain duplicates that are displaced from eachother by varying (and sometimes significant) distances due to relative inaccuracies between the datasets. Yale and Gliese3 should only be combined with the RECONS dataset at most, and essentially represent “different versions of the universe” that are not as accurate as RECONS/DENSE/CTIOPI/LDWARF/HIPX. As such they are only useful for historical purposes and should not be used if accuracy is required.

Making 2D Maps

The standard way to present 3D stellar data in two-dimensional form (without distortion) is to project the stars onto a flat plane and mark the distance in lightyears above or below the plane next to the star. Fortunately, Astrosynthesis includes a method to generate such 2D maps, and as of the 3.01c update (now available) this exports the map correctly! It’s also possible to add FTL or trade routes to the maps if you’re using them for a Scifi setting (I’ll go into this more when I discuss the star maps from the 2300AD RPG in future blog articles).

The RECONS dataset is shown below as a 2D map, rendered by Astrosynthesis. Obviously, maps containing the larger datasets will be considerably busier than this!


 

SECTION 4: RELATED ARTICLES

This section connects you to the blog articles and updates that I’ve written to expand on the information presented here (topics will include how to use the Vizier stellar databases, and how the new lists affect the 2300AD RPG), so stay tuned for further updates!

Article: Historical Datasets: Yale and Gliese 3: I’ve moved the less accurate Yale and Gliese 3 datasets to a blog post to separate them from the accurate data presented on this Stellar Mapping page.

Article: How to make your own Stellar Database!: In which I describe how to use the VizieR database to make your own stellar database with Galactic XYZ co-ordinates (and how to import it into Astrosynthesis too)! The example provided is a corridor between Sol and the Pleiades (this dataset is included in Section 2 above) – 2300AD fans will recognise this as the Bayern corridor!)

Article: The 2300AD Near Star Map!: In which I compare the Near Star Map from the 2300AD RPG with the realistic distribution of stars in the solar neighbourhood, and find some interesting differences – the article also includes route maps and an animation! You’ll want to read this if you’re a fan of the 2300AD RPG!

Article Series: The 2300AD Realistic Near Star Map Project: A series of (non-canonical) articles in which I present how the Arms from 2300AD might actually look with a realistic star map!
Part I – Introduction
Part II – Overview


 

SECTION 5: DATABASE UPDATES

Sometimes stars are missed from databases for various reasons (e.g. they’re multiple stars whose parallaxes are difficult to determine), but I’ll do my best to track them down – any updates to the datasets on this site are listed here!

Updated: 25th May 2013: The LDWARF Galactic XYZ file contained incorrect data! The Z-coordinate values in the old file were all wrong (they were incorrectly calculated, and were actually the +X coordinates). I’ve replaced the Galactic XYZ file with the corrected data, and it is available for download in the LDWARF download section – thanks to Dr Charles Gannon for getting me to look at it again! (The Astrosynthesis XYZ file was fine, so that doesn’t need to be replaced).

Updated 25th Mar 2012: Added the LDwarf dataset, updated the Pleiades Corridor to HIPX, and updated the HIPX and CTIOPI datasets to include multiples. See this article on my blog for all the details!

Updated 24th Mar 2012: Moved the Historial datasets (Yale and Gliese 3 Catalogues) to a separate blog post, to separate them from the realistic data on this page.

Updated 12th Mar 2012: Replaced New Reduction Hipparcos data with Extended Hipparcos data – further details can be found in my blog.
Also, this Stellar Mapping page has received the Atomic Rockets Seal of Approval (proudly displayed at the top of the page)! :)

Updated 27th Feb 2012: Added CTIOPI dataset and edited DENSE dataset. Reorganised Stellar Mapping page and combined RECONS, DENSE and CTIOPI downloads. Further information is available at this blog post.

Updated 7th Feb 2012: HIP 55203 (Xi Ursae Majoris/Gliese 423) has been added to the Hipparcos CSV files. This star was omitted from the New Reduction catalogue because its parallax could not be accurately determined in the original Hipparcos data. However, ground based observations have yielded an updated parallax. See http://adsabs.harvard.edu/abs/1999A%26A…341..121S for details).

Updated 5th Feb 2012: HIP 84709 (Gliese 667) has been added to the RECONS CSV files. Technically this is a HIP star that is within 22.8 ly of Sol – for some reason it’s not on the RECONS Near Star List though (which is why it was missed). Note that this system’s positional data is determined from New Reduction Hipparcos data rather than from RECONS data.