Planets Without Stars or Mini-Solar Systems? 149
iamlucky13 writes "An article today on space.com discusses the discovery of 6 objects by the European Southern Observatory in Chile that are smaller than typical brown dwarfs, larger than Jupiter, and not orbiting any stars. The objects are surrounded by disks of gas and dust possibly similar to the early solar system. In addition to presenting astronomers with a new group of objects to study, the finding also deepens the debate over what makes a planet. The scientists responsible for the discovery sidestep the question by calling them 'Planetary Mass Objects,' or planemos."
True 'planets' then (Score:5, Interesting)
Comment removed (Score:5, Interesting)
Dark Matter (Score:5, Interesting)
I guess the question is how many of these would it take fill up the "dark matter" quotient we think exists.
Re:Dark Matter (Score:0, Interesting)
Why is this not the norm? (Score:3, Interesting)
For example, really how large a whack from a body with the right vectors is needed to send pluto escaping off in some mad direction? Anyone care to calculate how much force is needed to do it?
Re:True 'planets' then (Score:4, Interesting)
Not knowing the time scales involved, I'm just going to throw this out as a possibility: if the orbital period of these odd planets around the galaxy is large enough, then the gravitational landscape on each revolution will be so different that the odd planet will hardly have a regular orbit. Alternatively, could it not eventually be trapped by a star? If so, one could hardly call its journey from wherever it started to the capturing star an orderly orbit.
Star systems without a star (Score:3, Interesting)
but lack the mass to ignite a sustained fusion reaction in the core of the system.
How many others could be out there that we can't see?
Fun for the kids~! (Score:2, Interesting)
At the risk of being modded OT, this article reminded me of an awesome little trick an old physics teacher did to help us visualize how we got from the big bang to planet earth.
Take a small bowl, fill it with water. Then, add a handfull of dark sand. Let the sand sort of float in "space" for a bit, moving the water enough to keep everything floating.
Now, to "play God", simply twirl the water counter-clockwise (or vice versa if you live under the equator) and remove your hand. Behold: your universe of sand will form a planet in the center of the bowl.
And, just out of curiosity: has anyone else ever seen this, or was my Prof. a total crackpot?
No need. (Score:5, Interesting)
The Periodic Table of the Elements makes a lot of sense, because you can make a lot of predictions about the properties of an element based on where it is in the table. There are some oddities, sure, but by and large it is an extremely intuitive system. By comparison, knowing that a star is K or G tells you very little. You can make some inferences, by factoring in the abundances of the elements, the diameter of the star, the overall distribution of the electromagnetic radiation, etc, but if you're going to have to add in vast amounts of additional information to get anywhere, you might as well use that information in the name and have done with it.
For planets, asteroids, etc, it's much the same thing. By using too little information to determine the classification, you end up having to add vast amounts more information later on to produce subcategories, exceptions or new names entirely. That makes no sense to me whatsoever. Even a good naming system will need additions made to it, but it should be consistant with what is already there, and it should be easy to understand the relationships.
Since this is about planets, I'll use those as an illustration. Planets form around stars from the debris in the accretion disk, plus captured material from the stellar nursery in which the star formed, minus material "evaporated" from the system by the solar winds accelerating it, and minus material captured by other stars or gravitational sources. The process of condensing planets is slow, though apparently not as slow as once thought, which means that the material in the accretion disk will be sorted. In our own solar system, it seems to be that heavier elements are more common close to the sun and lighter ones are more common further away. (Mercury is unbelievably dense, for example, whereas Pluto seems to be little more than an iceball.)
However, because you need less energy to accelerate a lower mass, and because elemental hydrogen only forms a solid under extreme pressures, these will ALL have abundances of elements that are skewed (possibly by a lot, for inner planets, as the solar winds are much stronger) from the ratios observed on much larger scales (say, in the galaxy or the observable universe). Stars, on the other hand, are mostly composed of the extremely light elements and fit the expected abundances very nicely. As the gravitational field is reduced, the skew should increase, as it would require that much less energy for something to be ripped away, if it's free. (Obviously, hydrogen that has reacted with oxygen to form water is going to require much more energy than elemental hydrogen alone.) So, the composition tells us a lot about where something forms, how quickly it accumulated mass and how long it took. It would seem obvious, then, that composition should bear a major role in deciding what to call something.
The other "obvious" one would be structure. The "asteroid" recently observed to be 45% empty space (sand is 25%) would probably merit a new classification. Most asteroids probably have multiple "centers" around which they have congealed/collided. Certainly, the two comets that have broken up have had multiple centers, not a single rocky core. By comparison, the gas giants have a single center (duh!), as does the Earth and Venus, probably Mars as well, not sure if there's enough data on the others. But even with that, we can clearly see a logical distinction (as opposed to an arbitrary one) that can clearly distinguish between two very