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Zvezdichko
2011-May-18, 09:31 PM
http://www.nasa.gov/topics/universe/features/planet20110518.html

Now this is what I call really exciting.

Many, many planets who wander in space and don't orbit other stars

(... and I guess that some Nibiru-nuts will pick on this issue)

Hernalt
2011-May-19, 12:14 AM
"The survey is not sensitive to planets smaller than Jupiter and Saturn, but theories suggest lower-mass planets like Earth should be ejected from their stars more often. As a result, they are thought to be more common than free-floating Jupiters." I'd love for this intuitive idea to be confirmed. Imo a CHON, KREEP and space sushi meal-on-wheels.

Zvezdichko, you raise what I think is a useful anxiety about the interface between science and public. What is a Nibiru nut? Define it, set it in its taxonomy in relation to its nearest relatives. In the first order it's of course 'you know it when you see it'. I'm asking for second order.

E.g. We can say that galaxies pass right through each other with nary a stellar collision. But if I model the inner solar system in C and have a body pass by, I can make the moon leave the earth, the earth leave the sun, etc. I don't feel particularly nutty; I don't really know what a Nibiru nut is. :think: Is it someone who attracts or detracts from space knowledge? Is it for space exploration sound to eschew the common principle, 'any press is good press'? I do not have solid thoughts on these matters of interface between scientists and public, but I think it's where a lot of energy can be generated if contained correctly (i.e. not dismissed or let off as heat.)

Roger E. Moore
2011-May-19, 03:02 AM
http://www.nasa.gov/topics/universe/features/planet20110518.html

Now this is what I call really exciting.

Many, many planets who wander in space and don't orbit other stars

[checks watch] Just in time for the re-release of When Worlds Collide! Most righteous!

EDG
2011-May-19, 05:56 AM
The BBC article baffles me a bit:
http://www.bbc.co.uk/news/science-environment-13416431

from the article:

They detected evidence of 10 Jupiter-sized objects with no parent star found within 10 Astronomical Units (AU). One AU is equivalent to the distance between our Earth and Sun. Further analysis led them to the conclusion that most of these objects did not have parent stars.

Really? This sounds suspiciously misreported, and I didn't spot it in any other versions of the news elsewhere. I wonder if they meant 1000 AU or something.

Noclevername
2011-May-19, 06:04 AM
More likely they meant 10 light-years. Even 1000 AU is still close enough to be gravitationally bound to our Sun.

tusenfem
2011-May-19, 08:44 AM
from Zvezdichko's link:

The newfound planets are located at an average approximate distance of 10,000 to 20,000 light-years from Earth.

Although "auntie Beep's" is slighly differnt, they say:

They detected evidence of 10 Jupiter-sized objects with no parent star found within 10 Astronomical Units (AU).

Which does not mean they are 10 AU from our Sun.

EDG
2011-May-19, 10:26 AM
I don't think noclevername meant that he thought they were bound to our sun. He meant that if a planet can potentially orbit our sun at 1000 AU then (assuming that these are sunlike stars) planets should be able to orbit them at that distance too.

The problem I have with the statement on the BBC article is that a planet that is further than 10 AU from its star could still quite easily be bound to it (as the outer planets of our own solar system are), but the article seems to imply that they wouldn't be.

Jim
2011-May-19, 11:48 AM
The article I read said "1 billion miles," which is about 10 AU. Don't forget, these are Jupiter+ sized bodies. Keeping them in a stable orbit at that distance would be tricky and - as the article I read said - change how we view orbital mechanics/stellar system dynamics.

But, if they really are not orbiting a star, can they be called "planets?" In the old Greek meaning ("wanderers"), yes. But we tend to say planets orbit stars and these don't.

But if I model the inner solar system in C and have a body pass by, I can make the moon leave the earth, the earth leave the sun, etc.

Heck, just Google "Rogue Planet." He's done the modeling for you.

antoniseb
2011-May-19, 12:51 PM
... I don't really know what a Nibiru nut is. ...
There are people who believe that aliens have informed some of us that a giant dark planet will come into the inner solar system and disrupt things. In these stories, the planet is named Nibiru. Several reported dates for this event have come and gone. Z was just pointing out that this study shows that there are rogue planets out there, and Nibiru proponents may start chattering louder again.

antoniseb
2011-May-19, 12:59 PM
The article I read said "1 billion miles," which is about 10 AU. Don't forget, these are Jupiter+ sized bodies. Keeping them in a stable orbit at that distance would be tricky...

I suspect that the article's 10AU figure is a reflection of the minimum distance an L Dwarf could be from this 1-2Jm object without also causing a microlensing event. The evidence that some are free fliers would be statistical evidence based on how many were seen compared to stars. Orbital dynamics might be a factor, but I read it as just what the microlensing data could rule out.

John Xenir
2011-May-19, 07:56 PM
What is the estimated temperature of these planets? What are chances of some liquids not much below cloudtops? (if they are more gaseous H/He planets, like 4 ones of our system)

IsaacKuo
2011-May-19, 08:37 PM
I suspect that the article's 10AU figure is a reflection of the minimum distance an L Dwarf could be from this 1-2Jm object without also causing a microlensing event. The evidence that some are free fliers would be statistical evidence based on how many were seen compared to stars. Orbital dynamics might be a factor, but I read it as just what the microlensing data could rule out.
Ah, I think I get it now. The 10AU figure by itself seems a bit unconvincing, since Saturn is about 10AU from the Sun. But if the 10AU limit only applies to the lightest dwarf stars, then 10AU may be beyond the range at which a Saturn sized planet is likely.

Does anyone know if this study detected any bound planets also? I'm guessing not.

Jim
2011-May-20, 11:31 AM
Heck, just Google "Rogue Planet." He's done the modeling for you.

Arrrgh! Rouge Star. http://janus.astro.umd.edu/orbits/nbdy/rstar.html

Bynaus
2011-May-20, 11:46 AM
The problem I have with the statement on the BBC article is that a planet that is further than 10 AU from its star could still quite easily be bound to it (as the outer planets of our own solar system are), but the article seems to imply that they wouldn't be.

The point is that a survey of many nearby stars showed that detectable planets at 10 AU+ are exceedingly rare. Mind you: we do have the technical possibilities to detect them, as shown by the direct imaging of the Beta Pictoris planet (at ~8 AU around a very bright star). From the non-detection of planets in this survey, they calculated how likely it would be that the 10 MOA-events are due to 10 AU+ planets - and it seems that at least 75% of the MOA-events are due to free-floaters.


However, direct imaging, with adaptive optics, of planets orbiting young stars places upper limits on planets at wide separations. The Gemini Planet Imager has set upper limits on the number of stars with Jupiter-mass planets at semi-major axes of 10-500 AU. From these results, we estimate that <0.4 of the 1.8 planetary-mass objects per star are likely to be bound to stars at orbital separations of <500 AU (see Supplementary Information Section 8). Hence, more than 75%
of these planetary mass objects are probably unbound to stars if their typical mass is a Jupiter-mass or more.

From the paper on arxiv: http://arxiv.org/abs/1105.3544

borman
2011-May-20, 08:21 PM
I wonder if their Dark Mass/Baryonic Mass ratio was significantly lowered as a result of their hyperbolic gravity assist to escape speed.

Hernalt
2011-May-21, 05:09 AM
There are people who believe that aliens have informed some of us that a giant dark planet will come into the inner solar system and disrupt things. In these stories, the planet is named Nibiru. Huh. Thank you.


Heck, just Google "Rogue Planet." He's done the modeling for you.

Thanks for the Rogue Star link. Unfortunately it doesn't go below .08 solar masses. I coded for Jovian mass and have behavior of a 1 Jm Nibiru approaching 1AU perihelion from just-barely hyperbolic. Inside a tiny keyhole it absconds with earth and moon. Inside a small window it slings earth over escape velocity. Inside a wider window it imparts significant eccentricity. Then what I'll eyeball as 'survivable eccentricity' after 1.2 AU. Larger mass Nibiru(s) scale this outward. I don't know how to do probabilities wrt the ecliptic. At any rate, very remote odds, and that without listening to a sneaky scientist, who is always fudging data to get his next NSF grant.:whistle:

noncryptic
2011-May-22, 12:35 PM
"Astronomers, including a NASA-funded team member, have discovered a new class of Jupiter-sized planets floating alone in the dark of space, away from the light of a star. The team believes these lone worlds were probably ejected from developing planetary systems." - NASA

Apparently it is thought to be very unlikely that these 'planets' formed on their own, not in orbit around a star.

What reason is there to think that 'body formation' stops only (or almost exclusively) when that body ignites as a star?
I can see how the body being a star helps it to stop accreting even more matter (radiation pressure), but wouldn't the process also stop if there just isn't any more matter in the vicinity to be attracted by the body that's forming, and could such a body not just as well not have enough mass to become a star?

(Otoh such rogue planets - given their relatively low mass compared to stars - might be likely to be captured by stars, which might result in Jupiter-like planets with unusual orbits.)