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How did they detect 2015 BP519? On the diagram, it looks like the proposed Planet 9 is 10% farther than the detected object, but is 10x Earth size compared to t

How did they detect 2015 BP519? On the diagram, it looks like the proposed Planet 9 is 10% farther than the detected object, but is 10x Earth size compared to the size of a Kupier belt object. It seems like detecting the smaller inject would be the harder task yet Planet 9 remains undetected.

whatshisface 8y ago
There is some degree of luck in these detections: we can watch large patches of the sky at low sensitivity or small patches of the sky at high sensitivity, but at high sensitivity we cannot watch the whole sky at once (rather, choosing small patches to study).
nerfhammer 8y ago
there's only one planet 9 but probably zillions of dwarf planets. there are enough of them that it's feasible that you can stumble across one through something closer to dumb luck
InclinedPlane 8y ago
Imagine finding a penny on the sidewalk. Happens all the time right? Now imagine I asked you to go out and find a half-dollar on the sidewalk, but not just any one, a specific one. But don't worry, you don't have to look everywhere, it's almost certainly in one of the US states on the East Coast. That's the difference here. We don't spend all our time scanning the entire sky down to the dimness level that Planet 9 could be spotted, we simply do not have the resources. Our telescopes give a soda straw view, so we miss a lot of what's going on, most of it in fact. If someone knew already where Planet 9 was in the sky we could point our telescopes there over a few days and confirm it. But we don't, we only know a general area in the sky that it could be, and actually detecting it will require dozens of observations from some of the largest telescopes on Earth. On the other hand, we have detected lots of other objects in the Solar System that would be more difficult than Planet 9 to detect if we had to look for just them, but there are lots of those, and we find them easily by accident as we perform other observations or through surveys. Just as if we decided to go looking for lost change on sidewalks we could find a great many coins, but if we were tasked with finding a specific coin somewhere on the East Coast it would take a tremendous effort (or tremendous luck) to find it.

whatshisface 8y ago

There is some degree of luck in these detections: we can watch large patches of the sky at low sensitivity or small patches of the sky at high sensitivity, but at high sensitivity we cannot watch the whole sky at once (rather, choosing small patches to study).

nerfhammer 8y ago

there's only one planet 9 but probably zillions of dwarf planets. there are enough of them that it's feasible that you can stumble across one through something closer to dumb luck

InclinedPlane 8y ago

Imagine finding a penny on the sidewalk. Happens all the time right? Now imagine I asked you to go out and find a half-dollar on the sidewalk, but not just any one, a specific one. But don't worry, you don't have to look everywhere, it's almost certainly in one of the US states on the East Coast. That's the difference here. We don't spend all our time scanning the entire sky down to the dimness level that Planet 9 could be spotted, we simply do not have the resources. Our telescopes give a soda straw view, so we miss a lot of what's going on, most of it in fact. If someone knew already where Planet 9 was in the sky we could point our telescopes there over a few days and confirm it. But we don't, we only know a general area in the sky that it could be, and actually detecting it will require dozens of observations from some of the largest telescopes on Earth. On the other hand, we have detected lots of other objects in the Solar System that would be more difficult than Planet 9 to detect if we had to look for just them, but there are lots of those, and we find them easily by accident as we perform other observations or through surveys. Just as if we decided to go looking for lost change on sidewalks we could find a great many coins, but if we were tasked with finding a specific coin somewhere on the East Coast it would take a tremendous effort (or tremendous luck) to find it.