[X] My Assistant

[Guest_Myran_*]

NASA sponsored astronomer Michael Brown of CIT just announced he have found a 10'th planet.
The claim was made for one object based on its brightness alone and that for one object at 3 times the distance of Pluto. In short its smack in the middle of the belt of other KBO's.
The guy claim he was forced to reveal his data since a hacker had threatened to release information about the object.
Im strongly unconvinced about that story.
Why then claim it to be a planet rightoff. More likely think this guy must be looking for the fame of Clyde Tombaugh.
Without any infrared measurements or to establish the albedo properly which would have given a guesstimate of the objects size he singlehandedly claim a KBO planet, this should get the Bad astronomy 1'st price prize for preposterous extrapolation from a single unconvincing piece of scientific data.

[Guest_Richard Trigaux_*]

I think this debate is not by itself a astronomy/science debate: what is important is to study the objects, giving them a name is a lesser issue. However there was such an issue into biology, when scientists were to name the different animal/vegetal species and classify them (a much more complex problem than in astronomy). In the beginning it seemed an impossible task, as there was so many different species, apparent families and deep structures hidden under apparend diversity. It took centuries to disentangle this (an important stake, as the classification of species was the key to understand the history of life) and there are still some small moves taking place today.


I shall anyway try some classification, keeping with a "naturalistic mind".

-is a star something which has permanent nuclear reactions.

-a brown dwarf is a more ambiguous object, which has transitory nuclear reactions, or which at least shines like a star for a great span of time, one billion years or more. (In practice it is difficult to guess if an object has nuclear reactions or not. A clue is that deuterium is burned between 20 an 22 Jupiter mass. But smaller bodies without reaction can shine a long time like a small star).

-is a planet an unique object which orbits around one of the previous, more or less in a Titus-Bode step. A planet (with moons or not) formed from an unique original cloud or ringlet. On the countrary if this cloud or ringlet was unable to give a single object, but many objects which don't orbit around each other, then we have asteroids into an asteroid belt. With this meaning, Pluto is a planet, even if it don't have a correct positioninto the Titus Bode structure, while asteroids (Vesta) and KBOs are not, even if Vesta and its belt are in a correct Titus-Bode position.

-would also be a planet something free into space, but too small to fall into the star/brown dwarf categories. May somebody propose another name for this special category, something simpe and easily retainable for the general public.

-Is a moon an object which orbits around another which is not a star or brown dwarf.

-Is an asteroid an object which is wandering alone, or which is a part of a belt.


-For a star orbiting around a planet, I wait for observations of these. Please ljk1-4 quote your sources



We must also cope with a variety of structures for multiple systems. In multiple systems, we keep with the above classification of individual objects. So we have star-star systems, star-brown dwarf systems, with planets orbiting about any of their members. An important thing to understand is that the mass ration of a primary object in a system, over its secondary objects, are not much depending of the size of the primary. We could have for instance the solar system scaled up 30 times: the sun would be a blue giant, Jupiter would be a red dwarf, and Saturn a brown dwarf. If the solar system was scalled down, it could become a planet (or other name for this category) and Jupiter a moon.

It is also important to understand that multiple stars can also come into relatively equal sizes. For instance two stars of relatively equal mass are called double stars. With this in mind, the Earth-Moon system could be called a double planet, or Pluto-Charon also. But the recent discovery of other satellites makes the Pluto system a true planet-moons system, a true miniature of a double star system. So the concept of "double star" or "double planet" is not really relevant, unless the two objects are of relatively equal mass or have close relations like mass exchange. If they are real twins, in a sense. But there is no clear limit, so this classification is not very useful. Only prevails the habit of calling double stars, star systems which can be more unbalanced than the Sun- and Jupiter.

This classification don't remove any unambiguity, but it removes some mess. To make it complete, remains to name planet-like objects wandering alone in space (not bound to a star). Two categories:

-with moons
-without moons.