A Puffed-Up Extrasolar Planet

Maggie McKee writes, "New Scientist Space reports astronomers have found a planet less dense than a wine cork and 38% larger than Jupiter. It circles a star about 450 light years from Earth. A similarly bloated planet has been found before (HD 209458b), so these puffed-up planets may be quite common. But no one knows how they got so swollen. One possibility is 'that some poorly understood mechanism has separated hydrogen and helium in each planet.'"

Comments

Bloated?

[daeg]

Maybe it's just their time of the month. Better keep your distance.

Astronomers...

[/ASCII]

I love astronomy. In what other science does discovering two instances of the same thing make something potentially 'common'?

Reminds me of an old joke. An astronomer, a physisist and a mathematician are traveling on a train through Scotland. Through the window of the train they notice a black sheep.

"Aha," shouts the astronomer. "In Scotland, all sheep are black."

"Nonono, " says the physist. "We only know that there are black sheep in Scotland, not that all scottish sheep are black."

The matematician looks furiously at the other two and almost screams "In Scotland there is at least one sheep with at least on black side!"

Re:Astronomers...

[gEvil (beta)]

In what other science does discovering two instances of the same thing make something potentially 'common'?

When you consider that they've only observed an infinitesimally small portion of the universe, seeing two of the same thing suggests that there's a good chance there are more of them.

Re:Astronomers...

[/ASCII]

Nope. If you take a small number of samples from a very large and diverse population, the odds are actually very high that several of the very uncommon results (e.g. planet types) will be highly overrepresented. It's a variation on "there are so many extremely unlikely things which can happen that it's extremely likely that a few of them will happen."

Re:Astronomers...

[i_should_be_working]

A biologist, a physicist and a mathematician are sitting at a cafe patio sipping coffee and watching the people go by. They see two people enter a nearby building. A few minutes later three people come out of the building.
 
'Ah,' the biologist says, 'they must have reproduced'.
 
'Nah,' says the physicist, 'three is within statistical error of two'.
 
'Well,' says the mathematician, 'one thing is for certain: if someone walks into the building now, it will be empty'.

Re:Astronomers...

[cswiger2005]

Certainly, if you take ten samples and you find one of something then it's very likely it's actual rate of occurrence is less than 1/10.

I'm curious to see your reasoning for this. If you know that your sampling is not representative of the population, or you have a reason to suspect a bias which makes it more likely that you are finding instances of the "something" than if you had a lot more samples available, sure, I'd agree with your reasoning.

Re:Astronomers...

[ceoyoyo]

Okay, assuming you have a representative sample, no biases.

Let's suppose you have hat, with numbers in it. There are 10 tens and one each of 0-9. Each number 0-9 is relatively rare, compared to the 10s.

So let's draw a sample from the hat. Our probability of drawing a 10 is 10/20 or 50%. Our probability of drawing a NOT 10 is also 10/20. Suppose we draw two samples, one is a ten, one is a 3. Not knowing anything about the numbers in the hat (how many there are, how many of each kind there are or even WHAT numbers are there) we might decide that there are likely similar numbers of 10s and 3s. If we draw a second sample and it comes up a 10 we might think there are half as many 3s as 10s. From this population our simple estimate of the population is only accurate (judging 3 to be 1/20) if we actually draw every single number!

In a population that is very diverse (there are lots of individually rare items) your chances of drawing any PARTICULAR rare item are very low, but your chances of drawing A rare item are quite high. And we only ask about the rare items when we do find them.

So with a sample of one puffy planet out of ten samples we have three possibilities. 1. Puffy planets might be very rare and we happened to find one. That's unlikely but possible. 2. Puffy planets represent about 1 in 10 planets. That's possible, and fairly likely. BUT, equally likely is 3. Puffy planets are very rare but the population of planets is very diverse.

3. is even more likely since our observations do show us that there are lots of different kinds of planets out there.

Now, if you take an eleventh sample and it's another puffy planet, 3. becomes much less likely (if puffy planets are rare it's unlikely we'd draw two of them in such a small sample) and 2. more likely.

Re:Astronomers...

[cswiger2005]

Excellent reply; thanks. Of course, I believe the TFA said that astronomers have seen two "puffy" planets out of ten samples being drawn, not just one; but your point about the difference between a PARTICULAR rare item versus a SPECIFIC rare item is still relevant until we get enough samples to have a better feel for the variation out there.

We've observed around 180 exoplanets via Doppler and have ten which perform transits; how many do we have to observe before we start getting a feel for the more common variants versus the rare exceptional categories...?

marshmallow

[gEvil (beta)]

Maybe they're made of marshmallow. You ever seen how big one of those things can get in the microwave?

Drats!

[Atomm]

When I read Puffed Up Planet, I thought it was new geeky cereal. :(

Good grief.

[julesh]

If the cork is 1.38 Jupiter Volumes, how big was the bottle?!?

Re:Good grief.

[bunions]

> If the cork is 1.38 Jupiter Volumes, how big was the bottle?!?

about 460 billion km: http://www.physorg.com/news63346824.html

Ah, the speculation

[jense]

So, a twice-observed occurence makes a possibly common universal feature, and to explain it, we have a poorly-understood mechanism that somehow does something we don't understand with an effect we can't mimic. Ah, the joys of physics. :-)

Two is impossible..

[Kozar_The_Malignant]

"The number two is impossible," - Isaac Asimov in The Gods Themselves.

The meaning being that there may be none of something in the universe, there may be one of something, but if there are two, there are lots more than two. Actually, in this case he was referring to universes themselves, not just things in the univrerse, but the point is the same.

Re:Two is impossible..

[EsbenMoseHansen]

Counterexample: Regular polyhedron in ( 3 dimensions ): The tetrahedron, hexahedron, octahedron, dodecahedron, icosahedron. That's 5, and all there is.

And on the topic at hand: The claim were that these things are common. If they are really rare, there might still be a lot of them.

Mating Displays

[the phantom]

I think it is facinating that scientists can now observe the mating rituals of planets. I assume that these planets are making themselves look larger for potential mates. Soon, we will have scores of baby planets running around, which might answer questions about litter sizes among planets.

Re:Another possibility

[merlin_jim]

Maybe these bloated planets are the only large enough for us to be able to see at this point.

There are certainly limits to the lower range of sizes of planets we can detect - and since most detection methods work based on gravitational influence, it is apparent that a large worlds close in to its sun will be easier to detect than a small one far away.

Many of the first planets we found were very large with very close orbits, however recently we've been able to detect terrestrial - "rocky" that is as opposed to gas giant (none earth sized or smaller yet, alas) - planets around other stars

So while these planets may in fact be common (and I would suspect internal heating more than some esoteric mechanism that we don't understand to explain their densities), we also know of many other types of planets - the most common being dense hot giants with very close orbits to their primaries...