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Are We Missing Nearly All Nearby Planets?

07/25/2012 4:54 PM

Just read a story about the 2,300+ planets thus far discovered, using the "Transit Method". This is the method where the brightness of the star lessens whenever a planet transits in front of it (from our point of view).

But it brought this thought to mind: In order for the planet to transit the star from our point of view, there is a relatively narrow window of how that planetary system must be aligned. The plane that is formed by the orbital path of the planets must be nearly coplanar to the view from Sol. Otherwise, the planets will never come between us and the distant star, no matter if there are 100 planets in that system. They will all remain undetected.

So as all these astronomers are observing all these thousands of stars, for the flicker, and eliminating the ones that come off empty... the truth appears to be that most of them could potentially still have planetary systems; given the very few degrees, out of 180, that will allow the Transit Method to work.

Does anyone have any idea of the success ratio that this method has? I mean, most of the possible orbital planes will not allow the method to work. Although it's apparently the best method available, it seems much more inefficient than I'd first considered it to be.

My non-Euclidean geometry is not quite up to par for this one.

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#1

Re: Are We Missing Nearly All Nearby Planets?

07/25/2012 7:11 PM

It's worse than that.

You are correct that there is no special alignment of other solar systems relative to the ecliptic of the Milky Way. This means that many star systems will fail to present the opportunity for a transit detection.

However, transits need to be fairly quick to detect the event. Most of the planets we have detected have very short orbital periods. Longer periods are going to be harder to detect for a number of statistical reasons.

The fact that we see so many of these transits with the restrictions required to see their transits simply tells us that planets are not uncommon. Recent studies suggest that every star has at least one planet in our Milky Way. That is at least 100 billion planets!

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#2
In reply to #1

Re: Are We Missing Nearly All Nearby Planets?

07/25/2012 7:32 PM

If we should survive another 300-500 years without annihilation, I deeply envy our interplanetary explorer descendants.

Sagan's "billions and billions and billions" has just been trumped. The numbers are incomprehensible; as are the possibilities.

I'm humbled

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#3

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 12:07 AM

Euclid is fine, alive and kicking.

Yes, the star, the planet, and we have to be in the same plane, to make the observations. If you consider that the bulk of the Milky Way stars are observed within a +/- 2degree angle, the rest may not matter much at all. Within that, the choices narrowed further. If you consider earth like planets, it is a fraction of a degree, where the planet can transit across the face of its star. It is a fraction of a degree, thru we view it. And the two angles do not align, except by a minor miracle.

So, the chances are between nil and minimal, that we can observe it at all!!

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#4

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 12:40 AM

It seems to me that we need to develop the capability of interstellar probes, to physically examine nearby star systems.

A fusion-pumped Ion drive looks promising, as does the Searle effect for reaching relativistic speeds. However, alas, we are underwhelmed by the current lack of progress in these areas.

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#5
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Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 12:49 AM

All we need is some transparent aluminum and a few Dilithium Crystals, some Beresium modified Corbomite and we can go.

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#6
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Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 8:12 AM

It's held up in customs, unfortunately.

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#14
In reply to #6

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 12:36 PM

They're waiting for a Klingon translator.

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#7
In reply to #5

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 8:33 AM

Cavorite perhaps?

More seriously, if Venus had a lower abedo, we would have difficulty finding it, 2 transits 4 years apart, ever 109 years, and only lasting 7 hours.

There could be a googol of planets out there!

Dave

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#8
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Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 8:40 AM

How does the planet's albedo effect transit detection?

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#9
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Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 8:57 AM

I do not believe that's what he was suggesting ~ he stated:

"if Venus had a lower albedo, we would have difficulty finding it"

His further statement:

"2 transits 4 years apart, every 109 years, and only lasting 7 hours" suggests that it would be unlikely for us to have detected it via transit-method due to the infrequency of transits...

No matter HOW we look at it, the heavens ARE a wonder to explore ~ !

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#16
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Re: Are We Missing Nearly All Nearby Planets?

08/21/2012 9:07 AM

Thanks for that, I was on holiday

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#10

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 9:00 AM

Okay, so we clearly need a different, more efficient method of detecting planets.

Seems to me that virtually ANY method that has any amount of success would be more efficient than Transit Method. The percentage of planets that we can potentially find this way vs. the number that we can't detect appears to be abysmally low.

Not that it isn't a fantastic leap forward, that we are able to detect any planets at all... considering the distances and relative sizes involved... but when I first heard about it, I hadn't really thought about all the things that must align. I figured if they check a star and find nothing, that's probably it. But that's not the case at all.

I'm curious to know what the next great leap forward may be, regarding planet detection; what particular technology will be the one that next advances, and takes us to the next level.

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#11

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 9:40 AM

Yeah, but once you find a perfect Earth clone, what are you going to do with it? We can't even take care of the one we got. It's best just to leave it alone and focus on keeping the one we got in a livable condition.

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#12
In reply to #11

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 10:01 AM

"We can't even take care of the one we've got"

That's about as subjective a statement as can be. I'm not sure how much taking care of it we need to do... or can do, for that matter. I think it can take care of itself. What we can do is try not to harm it more than necessary. But merely by being a "civilization", we do have effects on our planet. Basically our planet will be fine no matter what we do to it. We may change our environment so much that we kill ourselves off.... but planet Earth will always be fine. It has no obligation to be all that we need. It was here before us, and will be here after we are gone (unless of course a sufficiently large asteroid hits it).

But as far as "leaving alone" any planets that we find, especially Earth clones... I'm going to go ahead and totally disagree with that, on every level, and for more reasons than I could list. Pure exploration and advancement of knowledge being two reasons. Survival of our species is another. Population saturation. I could go on and on.

But this isn't the subject of my question. I'm curious about how many planets remain undetectable by current methods, and what the next steps in detection may be.

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#13
In reply to #12

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 11:26 AM

Better optics are expected through metamaterials research. So... better telescopes will help.

I do think the 'transit' approach is simply a shortcut to confirm that planets exist out there, while we are still working out the optics necessary to pick em up and do a proper catalogue.

But I also agree with other comments, that the technical challenge of difficult or unliveable habitats even here on this planet is something requiring mastery before we hope to venture off to some 'earthlike' other world... where 'earthlike' is pretty loosely defined and includes mercury-like and mars-like.... so close, but yet so far, eh.

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#15

Re: Are We Missing Nearly All Nearby Planets?

07/26/2012 12:47 PM

There is a difference between "discovering" a planet (naming it and getting its position in space) and theorizing about the number of planets out there. The transit method can only find an almost insignificantly tiny portion of all planets: certainly less than one in a billion. The method also gives some false positives.

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