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The radial velocity method is one of the primary tools that we have to find extrasolar planets. It's based on the idea that when a planet is orbiting a star, it will induce a "wobble" in the star that will be detectable to us as a slight shift in the spectrum of the star caused by relativity. This method is best for finding "hot Jupiters", massive planets in close orbits because this causes the largest oscillations in the star's position.
I propose that this method could be applied to the goal of finding new objects orbiting the Sun. Because the Sun is so much closer and brighter than other stars we should have the ability to detect smaller objects that are farther away. It may even be possible to use this method to find new Kuiper belt objects.
What do people think?
-Josh
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Not at all sure, but I'd hazard a guess that looking outward with IR might be another way to detect stuff out beyond Neptune. It's been proposed as a way to detect far more near-Earth asteroids, from a satellite to be placed near the orbit of Venus.
Detecting Doppler shift in the sun's light might prove a bit difficult, because the effect is small, while the sun's light is so overwhelmingly large. But, I'm no physicist. Maybe there's a way to see the signal without it getting swamped.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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It's my understanding that IR telescopes were the ones that were used to detect the larger Kuiper Belt objects.
Typically, the signal-to-noise ratio will go up with increasing signal. Because it's the light emanating from the Sun that we would want to detect this is a good thing. We could hone in on a couple of very precise spectroscopic emission lines and observe how they change. A Mars-mass object orbiting the Sun at 100 AU would generate a "wobble" in the sun with magnitude of .001 m/s. This will produce variations in wavelength in approximately 1 part in 10^11. For comparison, Gliese 581c has a radial velocity of about 3 m/s, which results in a variation in wavelength on the order of 1 part in 10^8. However, per square meter we receive more than 10^14 times as much light from the sun, so in the end it seems like it should at least notionally be possible to see some pretty small things.
-Josh
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