More on planets

You may recall that I posted on the Pluto controversy. Now it turns out that astronomers apparently have no idea what's going on.

Over the past few years, astronomers have found several extrasolar objects that by weight would qualify as planets, yet they lack what would seem to be the most basic of planetary prerequisites—a parent star. Many of these free-floating orphans are surrounded by disks of dust and gas with enough mass to coalesce into their own miniature solar systems. One of the orphans, which some researchers call planemos, may even have a planetary-mass object orbiting it.

The discoveries are blurring the line between planets and stars—and may bring about a revolution in thinking about planets that goes far beyond the Pluto debate.

It's worth reading, if you're into that sort of thing (Nerd!). Here's my summary: It was once thought that stars formed when an interstellar cloud coalesced into a giant mass with enough gravity to cause nuclear fusion. Planets were smaller chunks that were spit out during this process and orbited the star. But we observe a few things that don't fit this model. We have some planets that don't appear to orbit a star, for example. Then, there are brown dwarfs. These massive bodies were big enough to cause fusion, but were not big enough to sustain it, so they are big dark objects. The weird part is that there appears to be no clear line between a massive planet (many times more massive than Jupiter), and a small brown dwarf.

Whole thing here.