Lots of mass.
For an object to be a star (even a brown dwarf), some fusion must be going on in the core of the star.
For fusion to occur, you need temperature (millions of degrees) and lots of pressure (at that temperature, atomic nuclei tend to NOT approach each other, unless they are pressed together).
In order to get that much pressure, you need at least 13 times the mass of Jupiter in an object.
Or, if you prefer, Jupiter is only 1/13 of the minimum required to become a brown dwarf.
Even if we were to take ALL the material in the Solar system, other than the Sun, and dump all this matter into Jupiter (including all the planets, Earth, the Moon, the asteroids, the comets, the Oort cloud material, the Kuiper belt object...), you would still not have enough mass to create a brown dwarf.
If you wanted a "real" star, a star that fuses hydrogen into helium (a.k.a. a "Main sequence" star), you would need roughly 75 times the mass of Jupiter. That is something like 6 "minimum-mass" brown dwarfs lumped together.
For an object to be a star (even a brown dwarf), some fusion must be going on in the core of the star.
For fusion to occur, you need temperature (millions of degrees) and lots of pressure (at that temperature, atomic nuclei tend to NOT approach each other, unless they are pressed together).
In order to get that much pressure, you need at least 13 times the mass of Jupiter in an object.
Or, if you prefer, Jupiter is only 1/13 of the minimum required to become a brown dwarf.
Even if we were to take ALL the material in the Solar system, other than the Sun, and dump all this matter into Jupiter (including all the planets, Earth, the Moon, the asteroids, the comets, the Oort cloud material, the Kuiper belt object...), you would still not have enough mass to create a brown dwarf.
If you wanted a "real" star, a star that fuses hydrogen into helium (a.k.a. a "Main sequence" star), you would need roughly 75 times the mass of Jupiter. That is something like 6 "minimum-mass" brown dwarfs lumped together.
-
"A remarkable property of brown dwarfs is that they are all roughly the same radius as Jupiter. At the high end of their mass range (60–90 Jupiter masses), the volume of a brown dwarf is governed primarily by electron degeneracy pressure, as it is in white dwarfs; at the low end of the range (10 Jupiter masses), their volume is governed primarily by Coulomb pressure, as it is in planets. The net result is that the radii of brown dwarfs vary by only 10–15% over the range of possible masses. This can make distinguishing them from planets difficult.
In addition, many brown dwarfs undergo no fusion; those at the low end of the mass range (under 13 Jupiter masses) are never hot enough to fuse even deuterium, and even those at the high end of the mass range (over 60 Jupiter masses) cool quickly enough that they no longer undergo fusion after a period of time on the order of 10 million years. However, there are other ways to distinguish dwarfs from planets:
In addition, many brown dwarfs undergo no fusion; those at the low end of the mass range (under 13 Jupiter masses) are never hot enough to fuse even deuterium, and even those at the high end of the mass range (over 60 Jupiter masses) cool quickly enough that they no longer undergo fusion after a period of time on the order of 10 million years. However, there are other ways to distinguish dwarfs from planets:
12
keywords: and,dwarf,Whats,between,star,jupiter,brown,the,difference,Whats the difference between jupiter and a brown dwarf star