'Homeless' Planets May Be Common In Our Galaxy

sciencehabit writes "Our galaxy could be teeming with 'homeless' planets, wandering the cosmos far from the solar systems of their birth, astronomers have found. In a paper published online today in Nature, the researchers list 10 objects in our galaxy that are very likely to be free-floating planets. What's more, they claim that in our galaxy, free-floaters are probably so populous that they outnumber stars."

A new kind of space ship?

[definate]

Well, while I wouldn't think they'd be "space ships" in the classical sense.

I do wonder, would this not be a viable method of extremely long term, interstellar travel?

Find a "free-floater [urbandictionary.com]" (terrible name), build a perhaps subterranean civilization, somewhat colonize this planet, impart an impulse, and go for a ride for millions of years. Given we're advanced enough to even make it to one, we might even be able to attach "weak" but sustainable engines to it, such that we can slightly control it. It wouldn't be a terraformed planet, or similar, more like a moon, which we can live on, sustainably, regardless of the vacuum of space, and lack of sun. This would then essentially be a giant, "space ship".

Interesting idea.

Not really planets

[Xtifr]

Tch, they're not really planets, right? I mean, if they're not orbiting a star, then they can't have "cleared the neighborhood of their orbit". Yet one more reason the IAU's current definition is so idiotic. (Besides the fact that it suggests that Mercury is more like Jupiter than it is like Ceres.)

Re:Dark matter?

[thegreatemu]

There was some attempt a while back to assign dark matter to things like this, or free-floating black holes, brown dwarf stars, etc. I.e., somewhat exotic (or not) objects composed of normal matter.

However, in the past maybe 10 years, the constraints for dark matter come much more from cosmological arguments than from observations of the galaxy today. If you're interested, I'd suggest googling WMAP and baryon acoustic oscillations. The basic idea is that we can study the cosmic microwave background, which is the left over radiation as the universe cooled below a critical point some few 100k years after the big bang. In the CMB are embedded small fluctuations like ripples in a pond after you throw rocks in, which are the imprint of pressure waves spreading outward through the primordial plasma. By studying the size and spacing of these ripples, and applying a whole crapton of cool math, you can deduce things like the speed at which those ripples propagate, which is a direct function of both the total matter density and the baryonic (i.e. normal) matter density.

Of course I'm skipping all the details, but the basic result is that, although we first noticed dark matter from observing the motion of galaxies today, it was confirmed to a much better degree by observing the universe in its birth stages, and it's these latter measurements that tell us that dark matter absolutely cannot be due to the behavior of matter and general relativity as we understand it today.

generically expected; great if found

[hogghogg]

Free-floating planets are generically expected: Essentially all models for how solar systems like ours (and the others we now know) involve dynamical interactions that would kick out planets at high velocity, leaving them unbound. Astronomers have expected to find these for decades, but have been unable to do so because a planet not warmed by a nearby star gets cold fast (hundreds of thousands to millions of years) and therefore invisible even in the infrared. This result is very important if correct, because gravitational lensing is an emission-insensitive way to find the planets. And yes, IAAA! (ps As for whether they are "spacecraft": I love that idea, but the "people" onboard probably wouldn't give the planet an impulse themselves (way, way, espensivo), they would make use of a free-floater passing by and hitch the ride.)