Hubble Finds Wandering Planetoids

Canuckanuck writes: "The Space Telescope Institute which operates the Hubble Telecope has this story about the discovery of an unexpected hereto unknown population of wandering, planet-sized objects in the outer Milky Way that could be 80 times less massive than our beloved Earth. The viewing took place in M22 (a globular cluster) by way of microlensing. These things could be the smallest bodies ever seen beyond our solar system, which don't orbit a star. More information can be seen at JPL's website."

little bo peep says...

[msouth]

So _that's_ where they got off to. Thanks, NASA, I'll be out to collect them shortly.
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Formation is the Mystery

[bonoboy]

The way these things form is a real puzzle. The typical formation of these things requires a nearby nuclear furnace to provide the heavy elements such as silicon and iron. How these things formed in a globular cluster where the gravitational sway must have been so incredibly disruptive that no clear orbital path for accretion was laid out is the difficult part.

Recently in New Scientist there was an article on Megasuns. The theory is that before there were galaxies, there were gigantic stars, at some astronomical magnitude of a normal yellow dwarf's mass. There's apparently a number you reach where they get big enough to become stable again (think of a cubic mass distribution). My thought is that if these things somehow spawned galaxies, which are fractured thingies with accretion disks (bear with me) similar to an immature solar system's, then maybe it's possible that a)the globular cluster itself is a body more recently derived from a megasun than the Milky Way, thus having a less derived structure, and b) maybe that's where the planetoids come from? Accreted bodies orbiting a former megasun?

Bollocks, I know. A more plausible thought is that they're just in an area of such stellar density that shockwaves have somehow managed to form pockets of heavy materials which have accreted to form planet-like objects.

Back to scratching my arse..

Re:Formation is the Mystery

[bonoboy]

How do you account for the sheer number of them? The article called for a large number of them. If they managed to get away from stars in a globular cluster, don't you think the stellar density would have stuffed the orbital paths up so much that accretion to form tight planets would have been difficult? I mean, I can see a gas cloud remaining relatively stable, and thus bodies forming through shockwave interference, but suggestign planetoids all originated in stable orbits just seems really problematic in a globular cluster.

PS: I'm not a physicist or an astronomer..

Re:Correction...

[Canuckanuck]

You're right RareHeintz, I stand corrected. Geez, I even bolded the number! How dumb am I? Anyways, that's still a pretty small object when you look at the size of extrasolar planets that they've been finding to date by the "stellar wobble" method. How big are they? 10 Jupiters or so? 1/4 the size of Jupiter if freaking small, relatively speaking.

Dangit! Correction to my correction...

[RareHeintz]

First sentence should read:

That's 80 times as massive as Earth,

not 80 times less massive.

Must... preview... posts... Argh!

OK,
- B
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Re:Correction...

[RareHeintz]

Yeah, agreed, that's pretty damn small. IIRC, the largest extrasolar planets they've found are something like 1.7 Jupiter masses.

Anyway, all numbers aside, cool article.

OK,
- B
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Correction...

[RareHeintz]

That's 80 times as massive as Earth, not 80 times as massive. The other mass comparison was ~.25 the mass of Jupiter.

If the objects were 1/80 of the mass of the Earth - that's pretty much asteroid-sized - I doubt they could have been detected as microlensing events.

OK,
- B
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Re:Formation is the Mystery

[MichielB]

I think the most likely explanation is that these wandering planets are simply really planets, that somehow got away from their star.

What would happen to the planetaire systems of 2 stars if they pass eachother at say, less than 1 lightyear distance? Of course, most planets would simply be destroyed if such a thing happened, but a few of they are bound to get accelerated by the gravitational pulls and thrown away from the system.

I don't really trust the megasun theory. Sounds too far fatched for me.

Re:Planets or Something Else

[MichielB]

These bodies do not produce light! So you can not see them with telescopes, no matter how many you build. (well, maybe with a telescope the size of the solar system you could see the light of other stars reflecting of them)

You can only estimate their mass, and 1 space telescope is enough for that.

microlensing

[MichielB]

interesting thing is they didn't use a high enough sample rate while taking pictures (they never expected to find objects this small). So they can't really give a reliable estimate of the time the microlensing continued, which means they can't reliably estimate the mass of these objects. So the figure of 80 times as massive as our earth (and not, as RareHeintz points out 80 times less massive) is an upper limit. In reality this objects could be a lot smaller!