Quote:
Originally Posted by timb
That's wrong. The IAU working definition states objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets". Brown dwarfs are not stars, therefore no object orbiting a brown dwarf is a planet. If the brown dwarf orbits a star I suppose you could argue that its satellites also orbit the star, but that would be a special case. |
Don't know how you came to this conclusion.
But let me try and work this out:
1. Brown dwarves = greater than 13 Jupiter masses by definition, and burn deuterium - hence, Brown dwarves are stars, not planets
2. An object orbiting a brown dwarf which is less than 13 Jupiter masses and does not burn deuterium is a planet.
An object fitting #3's description has indeed been discovered orbiting an object matching #1's description, so yes:
At least one planet has indeed been discovered orbiting a brown dwarf, which * is * a star according to the IAU definition. It defines an object 13 Jupiter masses or more, deuterium burning, as fitting the description of a star - as that is exactly what a brown dwarf is: between 13 mJ and Red Dwarf in mass, and burning deuterium but not hydrogen and helium.
They are not main-sequence stars but they are indeed stars, IMO and according to the IAU definition you laid out.