Talk:2M1207b

Planet versus Moon[edit]

2M1207b is an interesting astronomical object that seems to test the definition of various classification schemes. If a brown dwarf is a star, then 2M1207b is a planet. If a brown dwarf is a planet, then 2M1207b would be a moon. 2M1207 does not orbit a larger object than itself, however.

I believe "brown drawfs" are neither a star or a planet, just as "dwarf planets" are not really a planet or an asteroid. The question then becomes: "Will astronomers adopt the approach that "brown dwarfs" can have planet(s) orbiting them?" Kheider 06:36, 30 September 2007 (UTC)[reply]

This would of course, introduce the question as to what to call an object that could not produce any form of fusion at any time in its formation, of sub brown-dwarf mass, but independent and not orbiting another body, if such bodies exist and if they could be detected.

These are currently called "rogue planets". At least until we understand more about these systems and how they form. Kheider 06:36, 30 September 2007 (UTC)[reply]

It doesn't seem obvious that brown dwarfs are necessarily universally called stars in all circumstances yet either. 66.248.122.173 01:24, 30 September 2007 (UTC)[reply]

Kind of reminds me of how once they realized that Pluto was smaller than predicted, Pluto was not called a planet by all. I see no problem with defining a middle group. But it will take understanding to accurately define such classification systems. Kheider 06:36, 30 September 2007 (UTC)[reply]

Since the mass of 2M1207 is 25 M_J and 2M1207b is 3.3 M_J, these objects would be a star and planet respectively. BlueEarth 17:22, 30 September 2007 (UTC)[reply]

True stars have a mass of at least 75 Jupiters and 2M1207 is no where near that. According to the discussion page at Brown Drawfs, Brown Dwarfs have not yet officially been declared as either. Kheider 16:40, 1 October 2007 (UTC)[reply]

Orbital period[edit]

The orbital period is a highly misleading quantity to put in the article. All we have is a projected separation, which is a minimum value of the true separation: basically we do not know the relative position in the radial direction: the companion could easily be several tens or hundreds of AU closer to or further away from us than the primary, and we would not know). Secondly we do not know the orbital eccentricity: it could be near periastron or apastron of a much wider/closer orbit. E.g. from this paper:

Depending on
projection effects, even the semi-major axis of 2M1207b might
be much larger than 46 AU.

All this means that the orbital period is an unknown quantity, presenting a value here overstates the current knowledge of the 2M1207 system. Icalanise (talk) 22:33, 27 June 2009 (UTC)[reply]

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