RISSO Catalogue

RISSO stands for Rogue InterStellar Straying Object and refers to all objects that are neither a "real" star (no red dwarf or upwards) nor orbit one.

These include free-floating brown dwarfs, sub-brown dwarfs, planetary-mass objects and planets drifting across space independently of stars. They fall through every grid, don't really fit into any category and are not mentioned in usual star catalogues.

Therefore, I have created a catalogue just in their honor.

RISSO Catalogue Version 2603 (first release) contains 869 objects, corresponding to 766 individual Rissos in 754 Risso systems and 103 planets orbiting them. 14 of these systems are less than 20 light-years away from Earth.

Source of data

The raw data comes from the website Exoplanet.eu. Their database contains all known objects outside our solar system that weigh less than 60 Jupiter masses (minimum mass). Or to put it another way, all objects that do not operate real nuclear fusion in their interior.

Astronomical objects between 13 and 60 Jupiter masses can fuse an atom with a proton (hydrogen + proton = helium), see deuterium fusion, but not two complete hydrogen atoms to one helium atom.

All exoplanets fit into this definition, whose listing is the actual goal of the operators of Exoplanet.eu.

If you delete the content of the filter box on their catalogue page and enter "star_name = null" instead, the list I downloaded and processed will be displayed. I removed entries with missing distances from it, renamed and converted columns.

Many thanks to the team at Exoplanet.eu. Since the database is regularly maintained and expanded, I will check back in time and bring my catalogue up to date.

Definition Risso

A Risso ...
• is a natural, round, at least planet-sized object
• is not a star, has less than 80 Jupiter masses (maximum value)
• does not orbit a star
• can form Risso multi systems
• can be orbited by planets

A Rissos can be of type or designation:
• brown dwarf
• sub-brown dwarf
• planetary-mass object
• free-floating planet

They form a star system, in the center of which there is no star, but at most a full-grown brown dwarf. Or just a planet with even smaller companions.

This means that a brown dwarf in the orbit of a Sun-like star is NOT a Risso, and exoplanets are even less so.

Well-known Rissos: Luhman 16, WISE 0855−0714, WISE J1711+3500, UGPS J0722-0540.

Also included in the catalogue, at least for the time being, are planets orbiting them, marked with lowercase letters at the end of their name. Equivalent companions that together form a multi-system are marked with capital letters, see explanations of the columns ident1, ident2 and type.

Seriousness

The data is real, the objects really exist and the catalogue was more than necessary, but none of this is meant to be 100 percent serious. It is not my job to define new cosmic object classes.

But let's take a look at the present and the future in equal measure. As of mid-March 2026, 85 star systems are known within a radius of 20 light-years, compared to only 14 Risso systems. A ratio of 6:1 in favor of the stars.

This ratio will be reversed dramatically very soon, I'm willing to bet on that. According to my prediction, there are far more Rissos out there than stars. We don't have the slightest idea of what is flying around between the glowing dots.

The better telescopes become, the more of the extremely hard-to-find, small, cold fellows are found. Sooner or later someone - presumably the IAU - will have to clean up the chaos around the Rissos and bring order to terms and categories.

Time is of the essence, because Risso-Hunter 1 is already warming up and Risso-Hunter 2 is fully assembled.

My bet

As of March 2026 we have ...
- 766 known Rissos
- 754 Risso systems
- 14 systems within a radius of 20 light years

My prediction for New Year's Eve 2035 (in 10 years)
- more than 10,000 known Risso systems
- more than 200 systems within a radius of 20 light-years
- at least one Risso at a maximum distance of 2.999 light years from Earth

That's my bet, anyone can pin me down to it.
Noted on 31 March 2026.
Signed: Martin Seydler

Columns + content

id	ID, ascending
name	Name/designation
type	Object-Type (m = main, c = companion, p = planet)
ident1	Fraction extracted from the name, which indicates the valence in multi Risso systems. A stands for the primary (Main), B for the Beta-Risso (Companion), lowercase letters indicate planets. No specification (empty string) means main Risso without known companions.
ident2	Same as ident1, but without parentheses ()
dist_ly	Distance in light years
ra_d	Right ascension in degree (0 to 360)
de_d	Declination in degree (-90 to +90)
mass_j	Mass (in Jupiter masses, mean value)
radius_j	Radius (in Jupiter radii, mean value)
discovered	Year of discovery
updated	Date of last record update by Exoplanet.eu
mass_j_min mass_j_max	Minimum and maximum mass (error range from/to)
radius_j_min radius_j_max	Minimum and maximum radius (error range from/to)
name_alt	Alternative names

Notes
Column id is not a Risso-id, but rather a sequential number, which may well change in the next version.

Known flaws

A handful of entries contain 0 values for mass_j, several hundred for radius_j. Hopefully, this will be corrected by a future update.

I haven't done any case-by-case checks of the objects, so there are erroneous entries that don't belong in this catalogue. I noticed GJ 1001 C at a distance of 40 light years, which does not have a main Risso assigned to it, and the actually existing star GJ 1001 (without C) is located at a distance of 12 light years.

Unfortunately, the Exoplanet.eu database does not contain any information for brightness (magnitude) and spectral type. This is a pity, some of the data can be viewed on Wikipedia, but both can be estimated with the help of the columns mass_j and dist_ly.

Companions or planets

The information in column ident1+2 cannot always be relied upon, which is due to measurement inaccuracy and its interpretation. This type of information may change in future versions.

If b is the planet of a brown dwarf, it can also be a double risso of two similarly sized brown dwarfs. In such cases, the b may eventually become a B or even C.

For this reason, I have left the 103 possible planets in the catalogue for the time being, although they make little sense without further data (orbital parameters). To filter out the planets, only the column type has to be tested for not equal to 'p'.

Conceivable extensions

This is the first version of which I still have to find out if I will be happy with it. It contains the most important data such as name, position and distance, so you know where to find them. Whether this is enough, I will find out after the first uses.

It would be possible to manually add missing data (brightness, spectral type,...), at least for Rissos in the immediate vicinity.

In addition, orbital parameters for the planets could be inserted, but I have not yet tested whether they are correctly entered in the database of Exoplanet.eu.

And maybe the division into name and ident1+2 could be improved.

It could therefore be that column names and content turn out differently in an update.

Download

The current version is RISSO 2603 or risso_2603 of March 2026 with 869 entries, based on a database query at Exoplanet.eu of March 13, 2026.

SQL

The SQL file creates a database table called risso_2603, preceded by a drop-table statement. A database and indexes are not created. The import file was created with the PHP database tool Adminer 5.4.1.

SQL-Download
⬇ dbstars_risso_2603.sql => 149 KB

Povray

The text file can be included in Povray and contains a string array with all the necessary information. Integer or float variables must be converted before use, as Povray does not allow arrays with different data types (string, integer, float) in version 3.7. I omitted data that is not absolutely necessary for the display when creating the file.

What such an array looks like can be seen in a mini-example.

Povray-Download
⬇ dbstars_risso_2603.inc => 88 KB

Animation

The video shows stars and Rissos up to 20 light years away from the Sun. Red stands for red dwarfs, yellow and white for sun-like or larger, our sun is shown as a pink ball in the middle.

The brown-black spheres are Rissos, additionally recognizable by the cryptic names such as WISE J0855-0714.

Further animations are in the works, this is only a first attempt. In fact, it is not easy to coordinate the different colors, sizes and text information well.
For more videos, see my blog post from January 2026.