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Alrighty then. Last time I left off at... saying a 0.4 metre aperture is insufficient for directly detecting extrasolar planets (exoplanets? that term is much more convenient to type and to say so why not use it instead?), even though it is sufficient to resolve the components. One problem: Magnitude 27 is very very dim. 6 is generally considered the cut-off for what can be seen with the unaided human eye (though many people's eyes are better or worse and light pollution can signifcantly reduce what is visible), so while the star is visible to the unaided eye the planet is more than ten thousand times dimmer. So we need to make sure our telescope is gathering sufficient light to even detect the planet.
*runs over to text-bearing bookcase*
Yes, this is basic stuff, and yes, I did have to look some up. In fact I was rather getting off on the wrong foot. Y'see, although a larger aperture helps to gather more light at once, dimmer objects can still be seen with a smaller scope if the integration time is increased. Doesn't work if one is observing with their own eyes - not being able to adjust exposure time and all. Actually, oh dear, I am rather afraid I might be spouting nonesense now. But I will correct my own errors as soon as I may, and sooner if they are pointed out to me. This is the kind of thing that will get one embarrassed looking back at the bloggings of their youth in years to come (well, actually actually what will really be embarrassing are the side musings I have not posted this past week on behalf of the illusion of focused discipline but that will just have to wait). Let us just go instead to the matter of contrast.
Oh, okay. (At least) One more diversion first. I find it interesting that an Earth-equivalent planet has an absolute magnitude only a little less than a Jupiter-equivalent (28.1[Woolf & Angel 1998] vs. 27 [Marcy & Butler 1998]). Being closer to the host star will make it still harder, though. Aaaanyway-
We already have telescopes capable of detecting such faint objects (e.g.), the difficulty is preventing the image from being washed out by the overwhelmingly brighter nuclear furnace sight right next door. Repeating myself enough yet? It is a sign of lack of thorough knowledge and clarity of thought. But if I work hard and study much that may improve.
What we need to do is find a way to suppress unwanted illumination so that what we are after is not obscured. Lessee, quote:
*runs over to text-bearing bookcase*
Yes, this is basic stuff, and yes, I did have to look some up. In fact I was rather getting off on the wrong foot. Y'see, although a larger aperture helps to gather more light at once, dimmer objects can still be seen with a smaller scope if the integration time is increased. Doesn't work if one is observing with their own eyes - not being able to adjust exposure time and all. Actually, oh dear, I am rather afraid I might be spouting nonesense now. But I will correct my own errors as soon as I may, and sooner if they are pointed out to me. This is the kind of thing that will get one embarrassed looking back at the bloggings of their youth in years to come (well, actually actually what will really be embarrassing are the side musings I have not posted this past week on behalf of the illusion of focused discipline but that will just have to wait). Let us just go instead to the matter of contrast.
Oh, okay. (At least) One more diversion first. I find it interesting that an Earth-equivalent planet has an absolute magnitude only a little less than a Jupiter-equivalent (28.1[Woolf & Angel 1998] vs. 27 [Marcy & Butler 1998]). Being closer to the host star will make it still harder, though. Aaaanyway-
We already have telescopes capable of detecting such faint objects (e.g.), the difficulty is preventing the image from being washed out by the overwhelmingly brighter nuclear furnace sight right next door. Repeating myself enough yet? It is a sign of lack of thorough knowledge and clarity of thought. But if I work hard and study much that may improve.
What we need to do is find a way to suppress unwanted illumination so that what we are after is not obscured. Lessee, quote:
The criterion for resolving and detecting objects of enormously different intensity needs some discussion. The planet does not have to be brighter than the local halo of scattered starlight, but its detection does require that, at a minimum, the random fluctuations in the halo due to photon noise be smaller than the planet signal.Well. Pause for thought. And... questions? ^_^
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Date: 2006-10-02 04:18 (UTC)From:how do you put a brain back together after it's been exploded? :O
xDDD I'm such a ditz xD
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Date: 2006-10-02 12:44 (UTC)From:~_~
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Date: 2006-10-02 20:25 (UTC)From:Could spectral shifts for elemental composition be used likewise? (I vaguely remember mention of an idea that we could use the shifts for nitrogen instead of oxygen to scan for life on distant worlds which made me think of this.)
Maybe even combine the two.
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Date: 2006-10-03 05:57 (UTC)From:Might (probably will) go into more detail later on spectral analysis (sounds fancy dunnit?) but off the top of my head I don't think nitrogen would work that well as it is a fairly inert gas. Ozone and methane are supposed to be very good markers though.
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Date: 2006-10-03 16:32 (UTC)From:Reactivity is not related to the spectral signature. Every compound absorbs light at different wavelengths. Now reactivity will have an affect on how intense the light needs to be for some reactions, usually those whose mechanisms involve radicals. Also, reactive compounds will likely be more difficult to find in all but fairly homogenous enviroments because they will react within a heterogeneous one.
What will be important is how distinct and easy it is to isolate specific compounds from the spectra since it will be a combination of everything. That should not be too difficult, however the intensity may not be enough to discern some elements due to noise. The amount of light elements in a star (which emits light) versus heavier ones in a planet (seen through reflected light and only near the surface) will have a signficant difference in magnitude. This may mean it is never viable without some really fancy techniques.
Nitrogen was just the example I remembered. Presumably one would want to look for as many heavy elements as possible for a rocky planet and lighter hydrocarbons for a gas giant.
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Date: 2006-10-05 09:22 (UTC)From:Ozone is thought to be a good biomarker because oxygen's reactivity is expected to remove it from a planet's atmosphere without the activity of life to put it back and ozone is more easily detected than the regular stuff. Methane serves as a biomarker too because it breaks down in the presence of oxygen so if we detect both in the atmosphere of a terrestrial planet we know there is a source producing it (hopefuly life but we have been fooled before).
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Date: 2006-10-05 13:44 (UTC)From:I cannot remember the exact reason for nitrogen being thought to be a good marker. I want to say it is because of its importance in the life-cyles of simpler life forms such as bacteria and plants, but my memory is a faulty thing.
With more and more extremophiles being found though, we can keep expanding the possible environments we can find life in, so it should give us more possible markers to test against. This is one of the things that excites me.
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Date: 2006-10-05 14:05 (UTC)From:I would not be surprised if we eventually find life in all sorts of weird environments throughout the universe eventually. For now we are sticking to looking for what we know though because otherwise we would have to look everywhere. :oP
Btw, thanks. I am actually starting to enjoy working on this project.
no subject
Date: 2006-10-05 14:09 (UTC)From: