Got Planets?

[BDanielMayfield]

With the current pace of exoplanary discovery, is it reasonable to assume that all or nearly all stars are orbited by at least one planet?

[geckzilla]

I don't think that the pace indicates anything like that. It indicates that there are a lot of planets out there to discover but there are still many, many more stars out there. If there is no way of detecting a planet around a star if it doesn't orbit it a certain way, how is there a way to look at each star and say whether or not it has a planet? So you'll have to look at models of planetary formation, not the volume of planet discoveries. I think we had a discussion somewhere in here about globular clusters or otherwise crowded environments being inhospitable to planets. I forgot if that's because they will likely get ejected or be less likely to form or both, though.

[BDanielMayfield]

I don't think that the pace indicates anything like that. It indicates that there are a lot of planets out there to discover but there are still many, many more stars out there. If there is no way of detecting a planet around a star if it doesn't orbit it a certain way, how is there a way to look at each star and say whether or not it has a planet? So you'll have to look at models of planetary formation, not the volume of planet discoveries. I think we had a discussion somewhere in here about globular clusters or otherwise crowded environments being inhospitable to planets. I forgot if that's because they will likely get ejected or be less likely to form or both, though.

Thanks for answering, but your answer made me wish that I had rephrased my question Geck. What I'm asking is; with what we know today, what can be deduced about the prevelence of planets orbiting stars? In math terms, in the set of all stars, what is the percentage that can be reasonably expected to be orbited by at least one planet?

[rstevenson]

The only thing we can deduce so far, based on the pace of discovery at least, is that our current techniques are likely to discover large planets orbiting close to their star, because that's what our techniques can do. We will learn a great deal more from the next generation of satellites, and even more from the satellites that are now on the drawing boards, so we'll just have to be patient.

I nevertheless expect that we'll find that planets are normal, at least around stars that are not in globular clusters or other environments where orbital interactions may prevent their formation.

Or, for your rephrased question, and ignoring globular clusters, I expect the answer to be almost 100%.

Rob

[Nitpicker]

... that are now on the drawing boards ...

How very quaint and 20th century.

[rstevenson]

I used to have a drawing board, giving it away just a couple of years ago. And my first "real" job way back when was as a draftsman. (That's how long ago it was; even the rare females doing the job were called draftsmen.)

But I admit to using drafting software for the last couple of decades or so.

Rob

[Chris Peterson]

With the current pace of exoplanary discovery, is it reasonable to assume that all or nearly all stars are orbited by at least one planet?

I believe the current estimate is that somewhere between half and all star systems contain planets. In addition, there is at least one planet for every star that is either in a distant orbit or no longer bound to its parent star at all.

[geckzilla]

Whoa, whoa, careful on your use of the word planet there, Chris. The IAU does not approve!

[Chris Peterson]

Whoa, whoa, careful on your use of the word planet there, Chris. The IAU does not approve!

Tough cookies.

[geckzilla]

I used to be ok with the whole pluto/planet thing because I think it's silly to categorize something emotionally. Mike the Pluto Killer Brown is anything but emotionless when he lords his win over everyone on Twitter anytime the subject is broached (which still happens with a startling regularity). It's pretty much just "It's this way because we said so." and one of the strongest arguments is that we should name things in a way that is "useful" and that's hard to disagree with except that usefulness is also somewhat arbitrary in this case.

Another argument is to say that Pluto is a planet like Europe is a continent, which is to say that neither is true. I wondered if Pluto was part of a continuum of objects also containing things like Earth, Jupiter, etc. If so, the line between planet and not-a-planet has been arbitrarily placed and doesn't necessarily make sense because saying dwarf planets aren't planets at all is like saying that they are their own continuum completely separate from everything else in the solar system. Didn't get an answer other than "that's difficult" or something to that effect. More of a dodge than anything. So I'm still a little confused on this area.

Yet another argument intended to diffuse the confusion created by putting "planet" in "dwarf planet" and then saying it's not a planet is to say that there are snakes called vipers that aren't vipers, among other terrestrial examples of naming mishaps. To me it seems more like a colloquial name has been mistakenly assigned to an animal. Why do this on purpose? The snake is not be a viper then it probably shouldn't be called a viper but the name is stuck due to tradition. Why screw up right from the start when there is an option to not call something a planet if it isn't a planet? Contrarily, a dwarf pear tree is still a pear tree. Of all the arguments this one is the most flimsy.

So on the one side we have a lot of people who are definitely emotional and just want the Pluto to be a planet (often ignoring Ceres, Vesta, etc) and on the other side we have some good arguments but they are just flimsy enough that one questions if they aren't themselves emotionally invested in the topic for adhering so strongly to them. I mean, they are good arguments, they're just not nearly as flawless as their adherents seem to think they are. Just to show how contentious this question really is, discussing it is banned at The Planetary Society's discussion board at unmannedspaceflight.com.

[Chris Peterson]

I used to be ok with the whole pluto/planet thing because I think it's silly to categorize something emotionally. Mike the Pluto Killer Brown is anything but emotionless when he lords his win over everyone on Twitter anytime the subject is broached (which still happens with a startling regularity). It's pretty much just "It's this way because we said so." and one of the strongest arguments is that we should name things in a way that is "useful" and that's hard to disagree with except that usefulness is also somewhat arbitrary in this case.

I simply call anything that is roughly spherical which orbits a star, or formed around a star, a planet. Beyond that, I use qualifiers. There are some definitions that are most useful precisely because they aren't rigorous.

[Beyond]

Tough cookies.

My mother used to say that at times. I wonder where it come from?

[Chris Peterson]

Tough cookies.

My mother used to say that at times. I wonder where it come from?

Was your mom a tough cookie?

[Beyond]

Not at all. I just never thought to ask where she got it from. Oh, wait... she may have picked it up from my sister.

[Chris Peterson]

Not at all. I just never thought to ask where she got it from. Oh, wait... she may have picked it up from my sister.

So your mom's sister was a tough cookie?

[rstevenson]

My mother made tough cookies. They could be used as weapons, and occasionally were -- especially if you said, where my mother could hear you, that they were tough.

Rob

[geckzilla]

I actually like crunchy, crumbly cookies. I thought everyone liked them like that for a long time but then sometime in high school maybe I learned that soft was the preferred texture.

[Chris Peterson]

I actually like crunchy, crumbly cookies. I thought everyone liked them like that for a long time but then sometime in high school maybe I learned that soft was the preferred texture.

Soft generally means they were made with too much sugar. I agree, a bit more crunchy/crumbly is better.

[geckzilla]

I think a lot of people simply bake them too long, having not invested in a timer with an alarm or simply by inexperience and not knowing how their pans and oven handle the heat.

[BDanielMayfield]

Got milk, to go with them cookies?

[Chris Peterson]

Got milk, to go with them cookies?

Goat milk.

[BDanielMayfield]

Got milk, to go with them cookies?

Goat milk.

That's goot.

I also like your inclusive definition of what constitutes a planet:

I simply call anything that is roughly spherical which orbits a star, or formed around a star, a planet. Beyond that, I use qualifiers. There are some definitions that are most useful precisely because they aren't rigorous.

[Beyond]

Not at all. I just never thought to ask where she got it from. Oh, wait... she may have picked it up from my sister.

So your mom's sister was a tough cookie?

haha, you must have been munching on a 'tough cookie' when you read my reply. My sister... not my mother's sister... my mother's daughter. My sister has been independent since she was a kid and some people used to take that as toughness.
Also, i like most cookies to be on the crispy side.

[rstevenson]

I actually like crunchy, crumbly cookies. I thought everyone liked them like that for a long time but then sometime in high school maybe I learned that soft was the preferred texture.

Soft generally means they were made with too much sugar. I agree, a bit more crunchy/crumbly is better.

The industry terms are "chewy" and "crunchy" -- and they are completely different beasts, made with quite a different proportion of ingredients. A soft (chewy) cookie doesn't have too much sugar in it, it has the right amount for a soft cookie. Examples of chewy cookies would be chocolate chip or molasses cookies. Examples of hard (crunchy) cookies would be ginger snaps or shortbreads.

Most of the time, if a cookie that should be chewy is hard but not crunchy, it just means the baker mixed them too much, developing too much of the gluten, or maybe they used the wrong kind of flour. But if they follow a good recipe and have some idea what they're doing, it's easy to make the different kinds consistently chewy or crunchy, as desired.

I know whereof I speak...

Rob

[geckzilla]

Chocolate chip cookies are good crunchy, though! I mean, I will cheerfully gnaw on one. I like the dried up bits of chocolate, too. I am not very picky when it comes to sweets. I just baked some brownies in two separate glass pans so I'd have all edges.