'Free-floating' planets found with no star in sight

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That sounds very close to me! Much closer than I'd expect.

Full article:
http://www.bbc.co.uk/news/science-environment-13416431

Thats very interesting.

That "within ten AU's" statement cant mean "10 AU's from US" because that would put them into our own solar system. It must mean ten AU's from each other at some spot way out light years away.

Ten Jupiter sized objects within a billion mile diameter volume of space ( Jupiter is 400 million miles from the Sun). Thats a rather crowded part of space.

I was planet geek in grade school and often wondered if there werent free planets wandering around between the stars. Even speculated that life could evolve on a free brown dwarf ( an overgrown jupiter like object) because such an object would be able generate its own heat but not be big enough to start atomic fusion and become a star- so it might be able to power its own life forms with out the light of a parent star.

I'm betting that "ten AU" is a mis-print or a misunderstanding from a press release. The way it's being used implies it is a volumetric measurement, but it's not. It's linear. The construction of that whole sentence is confusing. What's within ten AU? Us? The nearest star? The next Jupiter-like object? Did all ten objects fit within a ten AU cube? Unclear.

The Wikipedia entry for this reads a little different: http://en.wikipedia.org/wiki/Free-floating_planet

During a study published in 2011, the team found 474 microlensing events, ten of which were likely candidates for a free-floating Jupiter-like object. From this they estimate a density of about two of these free-floating planets for every star in the galaxy. (I'd like to see a much larger sample set before I buy into those statistics.)

An article in Science clarifies this somewhat: Of their ten candidates, none had a stellar object within 1.5 billion kilometers of the planetary object. So my guess is that's the ten AU the BBC article was referring to. This makes more sense.

Trouble is "1.5 billion kilometers" from the nearest star would put one of them closer to a star than Uranus is to the Sun which would put it inside of a solar system.

Im sure you're right that it is a misprint or misquote of somekind. I suspect that they may have astronomical units confused with parsec's. A parsec is like one percent of a degree of arc in the sky - a unit of measure astronomers use to measure a piece of sky - before they actually try to figure out the real size of the thing theyre looking at ( the moon and the sun take up the same amount of sky but the sun is 400 times as wide as the moon). They probably meant 100 jupiter sized objects within ten parsecs. That would make perfect sense.

Lets say you're sitting behind the batter's mound. The ump, the batter, the pitcher, and about 100 fans in the bleachers in the opposite side of the stadium are all in your line of sight and they all can be bocked from your view by your upraised hand. Your hand might be "ten parsecs" and all the above people are the "ten jupiter sized objects" even though they are all at different distances from you (and from each other).

Exactly. I think that's the criterion they're using for saying they're not bound to a particular star, but are instead free-floating. If there's no star within 1.5 billion kilometers, they're arguing that it's not part of a solar system.

But the objects themselves are quite distant from us.

I'm guessing the only way to get to the bottom of this is to find the original article in Nature, written by the astronomers who did the study. The language in a journal tends to be a lot more exacting than that used in a follow-up news article.

They are not 10 AU from a star, these planetars (the term I have heard used for rogue planets) are all within a 10 AU area of each other

Interesting article though TM, thanks. I've always found planetars to be very interesting and looked forward to the discovery of the first

It is also possible for a planetar to exist closer to a star, but be moving quickly enough that it is not actually in orbit/captured by the gravity of the star. Though no doubt many planets are extrasolar captures. One key indicator is thought to be a retrograde orbit

Vigilans, can you give a web or paper citation for this? I'm not doubting you. It's just that none of the articles I saw made this statement. I'd like to understand this better.

I'd suggest reading the writeup Phil Plait did on this:

http://blogs.discovermagazine.com/badastronomy/2011/05/18/the-galaxy-may-swarm-with-billions-of-wandering-planets/

Excellent write-up! Thanks! I like that he spelled out the interaction between MOA and OGLE. That was a really good cross-check on their data.

Just figured it out. One point five billion kilometers (1 billion miles) is the same thing as "ten astromical units".
So that explains where that ten AU figure comes from: its the closest of any of the ten objects is to a star.

So its neither the distance from us, nor from EACH OTHER. Indeed even the latter would be absurd. The diameter of the orbit of pluto is 80 AU's so it would mean that ten jupiter sized objects were discovered inhabiting a crowded efficiency apartment one eigth as wide as our own solar system! Not likely.

The author of the original article you found should be flogged by his editor for criminally negligent and criminally vague writing!

Nothing surprising. They really are nothing more than stars or small star systems that didn't make it. Matter shall congeal.

[quote="zer0netgain"]Nothing surprising. They really are nothing more than stars or small star systems that didn't make it. Matter shall congeal.[/quote

Low mass brown dwarfs. So what?

Thats like saying "unicorns. So what?"

Brown dwarfs only exist in theory. Theyve never actually have been seen as far as I know.

So? In something as big as the Milky Way alone, the odds of interstellar matter NOT having enough mass to ignite when it coalesced is high enough that it's quite probable they exist. Based on observation, a lot of things we believe is out there can't be absolutely proven.

Very interesting. There is more in heaven and earth than is dreamed of in our philosophies.

ruveyn

intriguing. obviously the ten AU referred to is not 10 AU from us, or else they would have been detected long before they came within that distance (by simple telescopic observation), and they would have perturbed the orbits of our planets catastrophically as they passed through the solar system.

i would think that they would also not be within 10 AU from another star, because they would not micro-lens the light of that star.

seen from light years away, a jupiter sized object would be seem very small compared to the sun, and therefore, the rays from the sun would go over and under and around the planet, and the arc of obstruction would be insignificant. the only way one would detect planets 10AU from a star, is for the brightness of the star to be reduced by a small amount as the planet passes in front of it, and therefore it could only be proven to be an orbital planet if this dimming happened in regular cycles.

the only way a jupiter sized object could micro-lens the light from a star, is if the apparent size of the star was much smaller than the object, and therefore the star who's light was microlensed would be very much farther away from us than the object (light years).

this leaves me to think that they may mean 10AU's from each other (in linear way (100 au long string)).
this could be the case if the planets once orbited a star that died, and lost so much mass , that it's unabsorbed planets would spiral off into space and then travel in a straight line at a speed equivalent to their previous orbital velocities.

i would think that when our sun dies, that the inner planets orbital velocities would be slowed due to drag from collisions with the expanding gases that buffet them in the red giant phase before the sun has lost sufficient mass to lose the inner planets, and they would be consumed into the sun before it contracted into it's helium stage. the outer planets however, would have no mechanism that would slow their orbital velocities, and they would then exit the solar system and drift off into interstellar space when the sun dies.

i think that scenario would be common, and these newly discovered "rogue" planets are the former satellites of their dead star.

whatever, it is just my speculation. i can not provide citations or references because i just thought about it in an arm chair way (and possibly came to as valid a conclusion as an arm chair would).