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Exo-Planet Question

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#1 Mister T

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Posted 21 June 2013 - 05:48 AM

I was watching Fraser Cain's newest informational video where he tries to answer "where are all the aliens?".

At one point he recites the figures about how many galaxies /stars / planets there are out there.

So I got to thinking about this from the other end...

Of all the stars we have studied and cataloged, are there any that we have decidedly ruled as having NO planets or proto-planetary discs or remnants of what once might have been planets?

if so how common is this phenomenon? (every time I use that word I want to follow with: de de dee deedee:jump:)

It seems while we are making great strides in discovering exoplanets, it is still a pretty rigorous and time consuming endeavor.

if we can say that there are a certain percentage of stars that don't have planets it can give us insight into how many there are that do. :question:

#2 Pess

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Posted 21 June 2013 - 06:45 AM

Very hard question to answer because of the extreme difficulty of detecting exoplanets.

Last article I read suggested that, on average, there is one planet for every star. (some stars have a bunch, some none--hence the average).

Exoplanets 'should' be common as current theory holds they will form out of the same dust and debris their parent star forms.

What is weird is why are all these Jupiter sized planets forming so close to their star? Or is it just those are the easiest for us to detect?

Pesse (Hot time in the old star tonight) Mist

#3 Ptarmigan

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Posted 21 June 2013 - 02:24 PM

Very hard question to answer because of the extreme difficulty of detecting exoplanets.

Last article I read suggested that, on average, there is one planet for every star. (some stars have a bunch, some none--hence the average).

Exoplanets 'should' be common as current theory holds they will form out of the same dust and debris their parent star forms.

What is weird is why are all these Jupiter sized planets forming so close to their star? Or is it just those are the easiest for us to detect?

Pesse (Hot time in the old star tonight) Mist


I think it is easier to detect a Jupiter sized planet orbiting close to their parent star.

#4 Qwickdraw

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Posted 21 June 2013 - 06:13 PM

"We dont know what we dont know"

#5 WaterMaster

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Posted 21 June 2013 - 06:48 PM

As the only way we can 'see' eco-planets is when they eclipse their star, we can only detect planets that are orbiting their star in a plane that is roughly parallel to our line of sight. We really don't know what we don't know, e.g. we don't know how many stars might have orbital planes that are perpendicular to our line of sight. Also, Ptarmigan is right, bigger planets, close to their star, are much easier to detect.

#6 Rick Woods

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Posted 21 June 2013 - 10:08 PM

if so how common is this phenomenon? (every time I use that word I want to follow with: de de dee deedee:jump:)


I do the same thing. :p
The evil influence of the Muppets.

#7 Kevdog

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Posted 25 June 2013 - 11:11 AM

Take our solar system and reverse the viewpoint. Go far away and look at it. If the planets were on the same plane as the viewer, then Jupiter would eclipse the Sun once every 9 years.... Saturn once every 20. So you have to be looking at the right star at just the right time and at the right angle. That must cut down the odds of detection a lot.

Can we see an earth/venus sized planet making an eclipse? I don't actually know.

#8 gavinm

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Posted 25 June 2013 - 03:31 PM

We can see the transit of an Earth sized planet.

But there are other ways of detecting planets. Most of the planetary systems with planets further away from their host have been detected by timing variations in the transits of the inner planets (resonance). There is also gravitational microlensing, which is very sensitive to planets further away and smaller.

#9 llanitedave

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Posted 25 June 2013 - 07:19 PM

All of these methods, however, will detect only a very small percentage of the planets that are out there -- and that only with a long-term and dedicated search program.

It should be enough, however, to give us a statistical probability that we can generalize for stellar populations as a whole, but probably not to make predictions about any given individual star.

#10 WaterMaster

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Posted 25 June 2013 - 09:41 PM

We can see the transit of an Earth sized planet.

But there are other ways of detecting planets. Most of the planetary systems with planets further away from their host have been detected by timing variations in the transits of the inner planets (resonance). There is also gravitational microlensing, which is very sensitive to planets further away and smaller.


Of course :foreheadslap:

See, we don't even know what we don't know. :p

#11 Qwickdraw

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Posted 26 June 2013 - 05:51 PM

As the only way we can 'see' eco-planets is when they eclipse their star,
Steve


Not true at all, we can see as you suggest variations in light intensity of the parent star, wobble due to gravitation between the star and planet, recently direct visual photography, orbital perpetuation of other known planets,

Well, I was going on my own but direct out of wiki is easier...

1 Established detection methods

1.1 Radial velocity
1.2 Pulsar timing
1.3 Transit method
1.3.1 Transit timing variation method (TTV)
1.3.1.1 Transit duration variation method (TDV)
1.4 Orbital phase reflected light variations
1.5 Light variations due to Relativistic Beaming
1.6 Gravitational microlensing
1.7 Direct imaging
1.7.1 Early discoveries
1.7.2 Imaging instruments

2 Other possible methods

2.1 Astrometry
2.2 Eclipsing binary minima timing
2.3 Polarimetry
2.4 Auroral radio emissions
2.5 Pulsation frequency

#12 Pess

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Posted 27 June 2013 - 08:53 AM

We use a technique in neurology where if we want to check a nerve that runs down the arm we can hook up electrodes to the skin along the path of the nerve and record electrical activity as it transits the nerve.

For example, say you suspect a nerve is impinged in the shoulder. You can put an elkectrode before the suspected point and one after and then poke the finger with an electrical shock and record the impulse as it runs up the nerve...see if the impulse passes the suspected 'impingment' site.

The trouble is, the skin has a lot of background electrical noise that drowns out the signal.

The reason I mention this is that the pickups are not very sensitive and nerve impulses are not very strong. So in order to get a readable signal you '*BLEEP*' the finger electrically a thousand times or so over 5 minutes and record each impulse. Gradually the signal you want will 'rise' up out of the background electrical noise.

I think with the next generation of space telecscopes (or even refined ground scopes) we will begin collecting enough light that computers will be able to 'average' the signal with a planet transitting against the starlight without the transit. The computer can then subtract the star light leaving just the planetary light to analyse.

Probably won't see any surface detail but it may be enough to get a spectral read off the planetary atmosphere.

...and that's all we need really to determine if life is active on an exoplanet.

Pesse (can't wait!) Mist

#13 Qwickdraw

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Posted 27 June 2013 - 03:52 PM

I think with the next generation of space telecscopes (or even refined ground scopes) we will begin collecting enough light that computers will be able to 'average' the signal with a planet transitting against the starlight without the transit. The computer can then subtract the star light leaving just the planetary light to analyse.

Probably won't see any surface detail but it may be enough to get a spectral read off the planetary atmosphere.

...and that's all we need really to determine if life is active on an exoplanet.

Pesse (can't wait!) Mist


We can already glean atmospheric spectrum of a exoplanets atmosphere Exoplanet's atmosphere is laid bare

I do not believe just detecting the spectra is enough to determine if life exists or not. Just detecting Organic Compounds does not give us information on their source.

#14 gavinm

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Posted 27 June 2013 - 03:52 PM

You can already do something like that. It's called Difference Imaging. Used mainly for gravitational microlensing in crowded fields, but I've also seen it used for transits. I've only seen it used for photometry, not spectroscopy. I tried it myself, but it was way beyond my programming ability :(

#15 Pess

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Posted 28 June 2013 - 08:30 AM


I think with the next generation of space telecscopes (or even refined ground scopes) we will begin collecting enough light that computers will be able to 'average' the signal with a planet transitting against the starlight without the transit. The computer can then subtract the star light leaving just the planetary light to analyse.

Probably won't see any surface detail but it may be enough to get a spectral read off the planetary atmosphere.

...and that's all we need really to determine if life is active on an exoplanet.

Pesse (can't wait!) Mist


We can already glean atmospheric spectrum of a exoplanets atmosphere Exoplanet's atmosphere is laid bare

I do not believe just detecting the spectra is enough to determine if life exists or not. Just detecting Organic Compounds does not give us information on their source.



I should have clarified and said 'Earth sized planets'.

There are many compounds in an atmosphere that would indicate industrialization.

However, the biggie would be the detection of a substantial percentage of Oxygen. Free Oxygen is bound up fairly quickly by its tendency to oxidize stuff.

Finding 20% of the atmosphere to be constituted of free oxygen and find other biomarker gasses such as methane, water or nitrous oxide would be pretty indicative of life as certain proportions of these gasses should not exist without atmospheric alteration by living processes.


Pesse (Just need to isolate the planetary light from the mother star) Mist






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