It would have to be a brown dwarf................or is that racist?................
“Or a red dwarf companion star with the mass of Jupiter.”
A Brown(not Red) Dwarf needs a minimum of ~13 times the mass of Jupiter.
http://en.wikipedia.org/wiki/Brown_dwarf
Red Dwarf are much bigger, I believe at least 60+ times the size of Jupiter.
The hypothetical planet Tyche is said to be only about 4 times the size of Jupiter.
http://www.independent.co.uk/multimedia/archive/00555/tyche3_555342a.pdf
“Or a red dwarf companion star with the mass of Jupiter.”
I have occasionally speculated, in my mind, on a non-standard theory of “alternative” “planet” formation.
Standard theory expects that all planets in a solar system are born of the same process as the formation of a solar system’s “sun”; that planets were further out in the “cooling” ring of material from which a sun and all it’s planets were formed.
But, that has always led me to the following questions.
If - across the entire universe, and even across our own galaxy - stars (suns) are not only dying all the time, are they not also (different ones) being born all the time?
In as much as all stars (suns) do not have 100% the same composition then would it not also be true that what is left when a star (sun) “dies” is also not the same; not the same as that star’s remnant but also not the same with regards to its “solar system”.
Since, what remains when a star (sun) dies is not always the same, then when a star “dies”, or after a star “has died”, is it not also possible that some rocky-core remnant or cooling gaseous remnant of a star, or of it’s “solar system” MAY, in time - pushed and pulled by all the stars around it (no matter how weakly from no matter how far away) - be pulled into the “orbit” (approximate gravitational-assisted direction) of another star (sun).
If that series of questions all have positive answers (if it could be proven) then it would demonstrate that not all “planets” in a “solar system” necessarily originate in that solar system.
What if years from now some form of “dating” shows some planet in our solar system with an orbit outside of our orbit (pick one) to be “older” than the “sun” is believed to be, by current “solar” science?
Now, either I am ignorant (in this realm of science) or nuts, or I need to “patent” this series of questions. /sarc