Wandering Worlds: Astronomy's latest unexplained phenomenon..

[jab1]

I posted this over at the latest creationist/evolutionist thread, but I think it deserves a thread of its own: "18 Planet-Like Objects Found Far From Stars."

The finding is certain to upset current theories of how planetary bodies form, several experts said.

They are considerably younger than predicted; they were found in a star cluster about 1,200 light-years away called Sigma Orionis that is no more than 5 million years old. Each "planet" is between five and fifteen times larger than Jupiter, the largest planet in our solar system. They were found by the infrared radiation they emit.

Bodies like these have never before been observed. They are so odd, astronomers are even debating what they should be called.

Part of the reason they have never before been observed is that we did not have the proper equipment until now. Another reason is that these objects are located in a unique place, unique in that it is relatively close and there is very little gas or dust to block the view. Also the sky is purty damn big and it takes time to search it all.

As indicated above, they were not predicted by current theories that try to describe how stars and planets form. This only means that the theories have to be changed or even scrapped entirely, but it certainly doesn't falsify the entire science of astronomy.

But you know some creationists will use this discovery to claim exactly that.

[Scylla]

I don't see what makes these objects any different from brown dwarfs. They're just smaller.

[tracer]

The article in jab1's link says:

Each is between five and 15 times as large as Saturn or Jupiter

This statement is needlessly vauge.

For one, by "as large as" it probably means "as massive as," not "as big across as." An object 15 times the diameter of Jupiter would be bigger than the Sun.

For another, Jupiter is over 3 times as massive as Saturn.

[John Corrado]

Originally posted by tracer
The article in jab1's link says:

For another, Jupiter is over 3 times as massive as Saturn.

Well, there ya go. The objects are five times as large as Jupiter, and fifteen times as large as Saturn. QED.

[Phobos]

Originally posted by jab1
As indicated above, they were not predicted by current theories that try to describe how stars and planets form. This only means that the theories have to be changed or even scrapped entirely, but it certainly doesn't falsify the entire science of astronomy.

But you know some creationists will use this discovery to claim exactly that.

This is no big surprise. Astronomy is full of things that don't neatly fit our definitions. Just recently, there was a big debate as to whether Pluto was a planet or just another member of the Kuiper belt. Lots of solar system objects fall somewhere between the definition of comet (ice + rocks) and asteroid (rocks with maybe some ice). Brown dwarfs are those objects not quite massive enough to be stars. I'm not quite sure why these objects are not considered brown dwarfs (dwarves?) ...probably because they're not massive enough to generate the same internal heat or something like that. I'd have to read up on brown dwarfs again. They wouldn't be planets unless they orbited a star.

This may not be the case here, but it's also not uncommon for a planet to form around a star and then be ejected from the solar system due to an unstable orbit. So there should probably be lots of free-roaming planets around.

[Akatsukami]

Phobos writes:

This may not be the case here, but it's also not uncommon for a planet to form around a star and then be ejected from the solar system due to an unstable orbit. So there should probably be lots of free-roaming planets around.

Actually, I believe that it was shown over a century ago that, in a three-body system, all three bodies were safe from ballistic ejection.

In a multiple-body system, of course, there is no proof, but I believe that most astronomers do not consider it likely that planets of a multiple star system will be ejected.

(Of course, there is considerable debate as to whether planets will form in a multiple star system.)

[tracer]

Phobos wrote:

brown dwarfs (dwarves?)

Believe it or not, the proper plural is "brown dwarfs."

The variant "dwarves" was invented in the middle of the century by Tolkien, for his Middle-Earth books. Earlier sources that discuss more than one dwarf invariably pluralized it as "dwarfs" -- including the Disney movie Snow White and the Seven Dwarfs.

[Wendell Wagner]

I thought that Tolkien revived rather than invented the plural "dwarves", but the more I look at the entry in the OED the less sure I am. Does anyone have a complete history of the plural form for "dwarf"? In any case, "dwarfs" is standard for referring to humans, stars, and any other metaphorical use of the word. "Dwarves" can only refer to legendary creatures.

[jab1]

Originally posted by Akatsukami
Phobos writes:

Actually, I believe that it was shown over a century ago that, in a three-body system, all three bodies were safe from ballistic ejection.

In a multiple-body system, of course, there is no proof, but I believe that most astronomers do not consider it likely that planets of a multiple star system will be ejected.

(Of course, there is considerable debate as to whether planets will form in a multiple star system.)

Well, this is why astronomers find these objects so strange: as far as they can determine, some of them were NEVER part of a solar system; they formed in isolation. Jack Lissauer of Ames Research Center said:

"...even those of us who would call them planets would not say they formed the way the planets in our solar system formed."

A few of these isolated planets may have been kicked out of conventional solar systems,but Lissauer is confident that most of them formed alone, in the same way as stars.

They were just never big enough to become stars, and yet they are also too small to even be called brown dwarfs.