by MarkBour » Wed May 04, 2016 3:52 pm
Okay, so you're 2000 light years away from Sol, and staring at it patiently with a bunch of CCDs. And this transit happens. It seems incredible that we could detect it. If we're talking about our Kepler spacecraft, I think Mercury occulting Sol might be too subtle to detect at that distance.
I'm guessing that the limits of observability with a given camera that can detect stellar variations depend on the luminescence of the star (as seen at the camera) and then the relative size of the planet and star. It seems it would not matter how large the planet's orbit was, since at that distance it won't affect the area of blockage during an occultation. (Admittedly, larger orbits produce fewer events per time.) Here on Earth, so close to Sol, the size of an inner planet's orbit will have a large affect on the size of the silhouette-disk we see. I assume we have never detected a planet that was at all transparent. If ever there was one, I guess that would have to be an additional factor in determining the thresholds.
Okay, so you're 2000 light years away from Sol, and staring at it patiently with a bunch of CCDs. And this transit happens. It seems incredible that we could detect it. If we're talking about our Kepler spacecraft, I think Mercury occulting Sol might be too subtle to detect at that distance.
I'm guessing that the limits of observability with a given camera that can detect stellar variations depend on the luminescence of the star (as seen at the camera) and then the relative size of the planet and star. It seems it would not matter how large the planet's orbit was, since at that distance it won't affect the area of blockage during an occultation. (Admittedly, larger orbits produce fewer events per time.) Here on Earth, so close to Sol, the size of an inner planet's orbit will have a large affect on the size of the silhouette-disk we see. I assume we have never detected a planet that was at all transparent. If ever there was one, I guess that would have to be an additional factor in determining the thresholds.