Not by my ctrl-f “Jupiter” on that page.
Jupiter is, however, the top of the list on wikipedia’s page for Y-type brown dwarfs.
This is a list of astronomical objects with the spectral type Y. They are a mix of brown dwarfs and planetary-mass objects.
Spectral type Y objects are not all brown dwarfs, they just have a similar elemental composition. Jupiter doesn’t have the mass to be considered a brown dwarf, they are 13-80 times the mass of Jupiter by definition.
That mass-based definition is outdated and does not consider recent observations of the interiors of Jupiter and Saturn made by the Juno and Cassini spacecraft. It is a reflection of cold-war era fusion chauvinism and is due to get an update. Jupiter is a star, Saturn straddles the boundary between star and planet.
Jupiter is a star, Saturn straddles the boundary between star and planet
I would suggest that a brown dwarf straddles the line between star and planet (the Wikipedia page begins with (“Brown dwarfs are substellar objects”) and that therefore Jupiter is, at best, straddling the line between star and planet, and therefore Saturn is solidly a planet.
Still no, from the first sentence of your article
This is a list of astronomical objects with the spectral type Y. They are a mix of brown dwarfs and planetary-mass objects.
That’s mostly because of the outdated IAU definition of the boundary between those genres being at deuterium fusion. Deuterium has a low abundance, and its fusion happens very briefly and early in the lifecycle of these larger dwarfs. That flash is not significant in the grand scheme of what these objects fundamentally are, is highly theoretical and has never been observed, and is more a reflection of cold-war era fusion chauvinism than an actual morphological boundary between object classes.
See that also seems to be using it as a point of reference? It labels it a “Y-class analog”, and every other entry on the list is much heavier and hotter. I’m just not sure.
That’s mostly because the heavier and hotter the object, the easier they are to detect by various means. We’ve only recently been able to detect Y-dwarfs and measure their spectral/chemical properties. We still cannot detect Jupiter-size Y-dwarfs beyond our solar system. Jupiter is analogous to the chemical and spectral properties that we’ve seen in these larger dwarf stars. However, that’s only the outer atmosphere, and that alone isn’t enough to conclude that Jupiter is a star.
The Juno mission has used gravity data to confirm that Jupiter’s hydrogen plasma has fully dissolved what was once the planetary nucleus around which the hydrogen accreted. This is the interior transition to stellar morphology.
Similarly, the Cassini mission has used ring seismology (studying waves raised in the rings by planetary seismology and mass anomalies) to confirm that Saturn has a partially dissolved planetary core. Saturn is an object that can be classified as neither a planet nor a star, and represents a class of transition objects straddling the non-binary border between these genres of objects.
See the following previous comment threads where I’ve fleshed out this argument in more detail and with references:
