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I am very not interested in observation and detection methods. At least not compared to the stuff they let us see. So I am trying to burn through this as quickly as I can while still at least giving the appearance of thoroughness.
Okay, (I am trying not to be so repetitive) the main things needed to be overcome to image extrasolar planets are:
Oh, whee! Just putting things into list form like this makes it look so much better. I feel like I am making rogress already. Anyways, skyglow is basically light pollutioon, it is the background glow of the sky caused by various sources of illumination such as city lights. If what you are trying to see is not brighter than the skyglow, forget about it.
Zodiacal light happens because our star system (and almost certainly others) is filled with countless dust grains making their own little orbits in the plane of the system. This dust scatters sunlight and makes the background of the ecliptic glow brighter than it otherwise would (in fact we are embedded in it and it fills the whole sky but it is brightest along the ecliptic cause thats where the planets orbit and especially near the sun in the sky and directly opposite it (called gegenschein in that case). Mostly it is very very dim and we won't see it ourselves, but it can still interfere with observing extrasolar planets, especially in the infrared.
Zodiacal light in other systems can also outshine any planets with its collective glow, if we let it. But at least its presence is still a good sign. The grains of dust have a short lifespan, they will spiral into the central star and vapourise within a relatively short time so if the glow is present we know a source of dust (such as asteroids) is there too.
Okay, (I am trying not to be so repetitive) the main things needed to be overcome to image extrasolar planets are:
- Contrast between nearby stellar brightness and far dimmer target
- Zodiacal light in the target system
- Zodiacal light in our system
- Skyglow (when observing from Earth [Honestly, who would?])
Oh, whee! Just putting things into list form like this makes it look so much better. I feel like I am making rogress already. Anyways, skyglow is basically light pollutioon, it is the background glow of the sky caused by various sources of illumination such as city lights. If what you are trying to see is not brighter than the skyglow, forget about it.
Zodiacal light happens because our star system (and almost certainly others) is filled with countless dust grains making their own little orbits in the plane of the system. This dust scatters sunlight and makes the background of the ecliptic glow brighter than it otherwise would (in fact we are embedded in it and it fills the whole sky but it is brightest along the ecliptic cause thats where the planets orbit and especially near the sun in the sky and directly opposite it (called gegenschein in that case). Mostly it is very very dim and we won't see it ourselves, but it can still interfere with observing extrasolar planets, especially in the infrared.
Zodiacal light in other systems can also outshine any planets with its collective glow, if we let it. But at least its presence is still a good sign. The grains of dust have a short lifespan, they will spiral into the central star and vapourise within a relatively short time so if the glow is present we know a source of dust (such as asteroids) is there too.
