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Back in 2019, SevenSpheres released a catalog of brown dwarfs (last updated in 2020), generated from the compilation by Wm. Robert Johnston. However, that source hasn't been updated since 2015, so one that was more up-to-date was in order.

That's where the UltracoolSheet comes in. Being from 2020, it contains the results of several surveys from recent years; the number of objects is somewhat less than that of the older catalog, but given that many of its entries were unconfirmed, the quality of the data more than makes up for it.

The following is the result of using some spreadsheet magic to generate a Celestia add-on from the UltracoolSheet, which after filtering out duplicate entries from the default data files (plus the exoplanet catalog by Sirius_Alpha), results in a grand total of 2819 ultra-cool dwarfs, spanning from the late M-type main sequence stars, to L, T and Y-type brown dwarfs. Over a hundred of them are actually binary systems, and three are triple, rendered here with approximate parameters.

Given that the original source doesn't contain physical properties such as radii or visual magnitudes, these have been taken from other sources or estimated using the COND03 isochrones, with some guesses about the age of each dwarf (as an example, if it's known to be a member of a moving group). That yields decent results in many cases: for instance, young dwarfs become more inflated than older ones, which are more compressed.


Limitations

• Since the last update of the UltracoolSheet, there are many recent discoveries which are missing. It's also very incomplete beyond 100 parsecs (that means no Teide 1, sorry )
• As just said, most physical parameters are guesses and may be significantly off in specific cases.
• Several of the dwarfs included here are companions to higher-mass stars, these not being dealt with here. As such, the distance values for them from other files may not match the ones of the companions, which can result in the components being separated by up to a few light-years. In some cases, the parent stars themselves may even be missing, if they're not bright enough to be in default Celestia!
• There may still be duplicates with other add-ons, especially if they don't use Modify/Replace.

For the future

• Many of the binary systems included here have determined orbits, yet those are currently not modeled here.
• Including some scripts for marking specific dwarfs (e.g. moving group members).
• And of course, here's hoping that the UltracoolSheet itself eventually gets an update!

That's it! Now enjoy your new solar neighbors

Update time! Back in April, I posted a new version on the Discord server, and over the last month, I've been further working on adding data from other sources, so that the catalog is no longer too out-of-tune with recent results. This includes data from Gaia DR3 (1399 objects get new parallaxes, 69 of them without prior values) and Kirkpatrick et al. (2021) (198 objects get new parallaxes, 28 of them without prior values). Physical properties also come in for over two hundred objects: for now only three sources are used, but I hope to expand this in further releases.

Age estimates are also improved: low-gravity objects get age ranges from Allers and Liu (2013) and Cruz et al. (2009); field objects (up to mid-T type) are assigned ages of 1 Gyr, following some studies which find the local sample of brown dwarfs to be biased towards young ages; and metal-poor subdwarfs now take 10 Gyr. This is also helped by a more robust assignment of objects to moving groups. A minimum probability of membership of 80% from BANYAN Sigma is considered, and some objects flagged as members but with missing/not high enough probabilities are now associated.

[Download in the above post]



Full changelog:

Spoiler

• Added coordinates and parallaxes from Gaia DR3 and Kirkpatrick et al. (2021).
• Added physical properties (radii, temperatures) from Filippazzo et al. (2015), Faherty et al. (2016) and Kirkpatrick et al. (2019).
• Filled in many of the missing distances, spectral types and companion position angles. (thanks to Gurren Lagann for tracking down missing distances!)
• Most temperatures are now estimated using the relations of Kirkpatrick et al. (2021), Filippazzo et al. (2015), Faherty et al. (2016) and Zhang et al. (2018).
• Fixed divergent distances of components in some multiple systems.
• Young objects without parallaxes now have distances estimated from the spectral-type-absolute-magnitude relations of Faherty et al. (2016).
• Improved assignment of objects to moving groups.
• Improved age estimates for low-gravity objects, field dwarfs and subdwarfs.
• Minor additions/changes to designations.
• Fixed some broken SIMBAD InfoURLs.
• Fixed triple systems.