'Hundreds of Worlds' in Milky Way

Raphael Emportu writes "BBC news is reporting that rocky planets, possibly with conditions suitable for life, may be more common than previously thought in our galaxy, a study has found. New evidence suggests more than half the Sun-like stars in the Milky Way could have similar planetary systems. There may also be hundreds of undiscovered worlds in outer parts of our Solar System, astronomers believe. Future studies of such worlds will radically alter our understanding of how planets are formed, they say."

Re:Aquatic life?

[KokorHekkus]

Not every day or time, it all comes down to in which environment it has to survive. And we have examples of tool-compatible appendages in aquatic life here on earth: the octopus that can open plastic bottles http://www.youtube.com/watch?v=wfRqYjv9QgA [youtube.com]. And then there are other aqautic life that seems to do very well without fins such as crustaceans.

Re:Not so Rare Earth

[Dunbal]

Yes, this is known as the Anthropic Principle [wikipedia.org].

not very wrong

[dominux]

a planet would not be 100% uniform liquid at room temperature. You don't get planet sized blobs of water. Our planet is a lot of liquid around a fairly small probably solid iron core. The most common liquid component of planet earth by a long way is magma. The solid rock crust and liquid water in the seas is so insignificant by comparison it is surprising we even bother to talk about it. Anyhow what you were probably thinking about is a planet with a surface completely covered by liquid water or something like it. I think something could arise on such a planet, at the surface (or possibly below it if we are allowed to assume a hot core with volcanic vents.) You could get algae mats forming and sinking when they die off. Huge floating mats could then provide an ecosystem for other things to evolve around. At some point there could be fishlike animals under the mats and amphibious creatures walking on top of the mats. I can't see any real limit to the size and stability of the floating mats. Any creature looking to develop technology would have to use organic materials, which makes electronics a bit tricky. In terms of leaving the planet, fuel and a launch pad wouldn't be too tricky, building the rocket might be though.

Re:can we make our minds up?

[mdwh2]

Indeed - the article also says:

Some astronomers believe there may be hundreds of small rocky bodies in the outer edges of our own Solar System, and perhaps even a handful of frozen Earth-sized worlds.

So it's reasonable that any Earth-sized bodies would be considered as new planets, but "handful" doesn't seem to account for "hundreds if not thousands".

Then again, I'm amused that this guy still seems to insist that there are 9 planets in our solar system, so either he slept through the recent decision, or he disagrees with it, and in both cases it's consistent that if Pluto is a planet, all those hundreds of other small rocky bodies should be too...

Re:not very wrong

[kels]

The most common liquid component of planet earth by a long way is magma. The solid rock crust and liquid water in the seas is so insignificant by comparison it is surprising we even bother to talk about it.

The Earth's mantle is a crystalline solid, with only tiny isolated pockets of magma. There is no vast magma ocean. The lower mantle is subjected to pressures that can keep it solid well above 2000 degree C. Much of the mantle deforms over millions of years, but it is not liquid.

The biggest liquid component of the Earth is undoubtedly the outer core, which is mainly molten iron.

Doesn't Anyone Read TFA ?

[mbone]

Apparently not, even at the BBC. What they were saying is that there could be hundreds of worlds in the solar system, not in the galaxy. (They meant in the Kuiper belt, far outside of Pluto and Neptune.)

We have already found 273 extra-solar planets [obspm.fr] in the galaxy. No one doubts now that there are millions, if not billions, in the galaxy, and a puling "hundreds" of Earth type planets in the galaxy would strike most people following this research as a very low estimate.

From the article : "Some astronomers believe there may be hundreds of small rocky bodies in the outer edges of our own Solar System, and perhaps even a handful of frozen Earth-sized worlds."

I would also regard this as almost not news at all, given the rapid rate of discovery of TNOs [harvard.edu] (Trans Neptunian Objects), three of which so far are the size of Pluto or larger.

Re:No shit.

[Yvanhoe]

That the chance of a star to have planets is one in a million. Doesn't seem impossible, does it? The survey of the closest stars around our solar system seem to contradict this. I don't have exact numbers, but too many planets were discovered within a 50 light-years radius to conclude that only one star in a million has a planet.

Of course the Earth could be located in a statistical anomaly within the Milky Way, but if you posit a uniform repartition of planets, there has to be more.

I am just nit-picking however. I fully agree with the rest of your post.

Re:But do we want them?

[Chemisor]

> Yeah, if you don't mind disassembling the whole planet.

Why should you mind? I'm not necessarily talking about disassembling Earth. We could start with Venus and Mars.

> The NIMBY people would be all over you and, frankly, I would join them on this one.

Why? The planetoids will not be anywhere near your back yard. In fact, if you stay on Earth, you don't even need to be aware of their existence. They'll be so far, you will not even be able to see them without a huge telescope. And it isn't like you have any particular use for Mars and Venus now. Both are uninhabitable, and while Mars might be terraformable, it is much easier to just plunk down a few beanstalks and turn it into a planetoid farm.

Just because it's rocky

[Pedrito]

doesn't tell you a whole lot. What we do know is that most of the extrasolar systems we've found also tend to have Jupiter-like and larger planets and that in the majority of cases, these planets are either fairly close to their stars or in highly eccentric orbits. Either of these conditions would tend to make any "habitable" planets less habitable. A Jupiter-like or larger planet close in or in a highly eccentric orbit would tend to destablize the orbits of any small rocky planets in the habitable zone.

There are so many things that have to come together to make our planet habitable, that I suspect these conditions are a lot less frequently found than a lot of people would hope. That's not to say I don't think is common in the universe. I do. I just think the vast majority (by several orders of magnitude) of it is going to be single-cell (or if not in the form of cells, of equivalent complexity). You need liquid water (which gives you a pretty narrow temperature range at any given pressure), you need something in the atmosphere to protect against stellar radiation (or, if it's a water planet, I suppose something in the water to protect), you need a planet that's active, but not overly active (and lots of factors go into that). Anyway, I suspect true earth-like planets are pretty rare.

Re:sweet

[spiffyman]

The explanation for the "write" vs. "write to" distinction, at least, is pretty simple. The nouns taking the verb "write" are dative case. That's not obvious in English, but it's there, and it underlies the apparent form.

German is useful here because 1) it's the root language for English and 2) its sentence structures can be perfectly analogous. Take the German sentence Schreib deiner Mutter einen Brief which is translated word-for-word as Write your mother a letter. In German, the deiner is a clear marker that Mutter is dative. The exact same thing is happening in English, but since we don't decline our articles or possessive adjectives and rely instead on word order, it's not obvious to the typical native speaker.

Re:No shit.

[Actually, I do RTFA]

How do you know that tidally locked planets are commonplace? There are none in our system.

None, except for Venus...

But yes, I agree most of the numbers seem like poor WAGs, and the water point seemed redundant.

Re:No, YOU are confused.

[meringuoid]

Our galaxy is 50000 ly in radius, which comes out to 1.4e37 m2. Our solar system, taken to the orbit of Pluto, is 40 au in radius, or 2.8e24 m2. The ratio between the two is 5e12.

Remember that the Galaxy is a three-dimensional volume, while Saudi Arabia is flattish. According to Idle et. al (Significat Vitae Carmen Galactica, 1983), our Galaxy itself contains a hundred billion stars and is a hundred thousand lightyears side to side; it bulges in the middle, sixteen thousand lightyears thick, but out by us it's just three thousand lightyears wide. Taking the lower thickness, that gives a Galactic volume of pi * (50000^2) * 3000 = 2.34x10^14 cubic lightyears = 2.00x10^61 cubic metres. Taking the Solar System to the orbit of Pluto, that's 2.86x10^5 cubic AU = 8.97x10^38 cubic metres. Ratio of the two, that's about 2.2*10^22. Allowing that Saudi Arabia is on average covered by one metre's thickness of sand, we get a grain of sand about half a millimetre on a side.

Re:can we make our minds up?

[Impy the Impiuos Imp]

Well, I think the problem was that one reasonable definition of "planet", "a mass large enough that its gravity pulls it into a ball" leaves us with 50-something planets in our solar system.

Re:No shit.

[HiThere]

Sorry, there are lots of tidally locked bodies in our system, Luna would be called a planet if we were at all objective. It's tidally locked (to Earth). Mercury is tidally locked...it's a resonant lock, but it's still a lock. And Mercury *IS* called a planet.

Still, any planets that are tidally locked will be very close to some larger body. If they're close to the sun, then they'll be out of the liquid water zone. If they're close to something else, then I don't see why that should exclude them as a home for life.