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I'm pretty sure there is some reason I'm missing, but I really don't understand why its really difficult to find a planet in the Solar system (or at the edge) w

by sv12l 8y ago

I'm pretty sure there is some reason I'm missing, but I really don't understand why its really difficult to find a planet in the Solar system (or at the edge) while we are hearing lot of news them finding exo/non-exo planets at the distant galaxies? Why are these planets so elusive to our so advanced eyes/lenses in our orbits?

mehrdadn 8y ago
I understand the reason is that we only detect distant planets indirectly, by looking at the behaviors of the stars they block. With planets in the outer solar system I guess they're too small (angle-wise) to be blocking anything we can easily examine.
- sv12l 8y ago
  That make sense, thanks
- nkrisc 8y ago
  The reason that's difficult to do with planets in our own solar system is because we are also orbiting the same star. Detecting exo-planets transiting their host star is possible because we aren't orbiting that star. We could never observe this planet transiting the Sun because it never passes in between the Earth and the Sun. And if it did, we probably would be quite aware of it already.
Tepix 8y ago
It's hard to detect dark, cold things that are far away. Planet Nine is very cold, likely to be quite dark and also very far away (anywhere between 200 AU and 1200 AU depending on where it currently is in its orbit). Its estimated apparent magnitude is greater than 22.5. That means you'll need a large telescope (I guess around 5m), a dark sky and sensitive cameras to be able to see it. Stars are neither dark nor cold, however brown dwarves that are pretty cold are much harder to detect. If you look at the list¹ of the sixty nearest stars to our sun, you'll notice that many close brown dwarves have only been found fairly recently (e.g. Luhman 16a/b, 6.5ly away were found in 2013). ¹ https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brow...

by sv12l 8y ago

mehrdadn 8y ago

I understand the reason is that we only detect distant planets indirectly, by looking at the behaviors of the stars they block. With planets in the outer solar system I guess they're too small (angle-wise) to be blocking anything we can easily examine.

sv12l 8y ago
That make sense, thanks
nkrisc 8y ago
The reason that's difficult to do with planets in our own solar system is because we are also orbiting the same star. Detecting exo-planets transiting their host star is possible because we aren't orbiting that star. We could never observe this planet transiting the Sun because it never passes in between the Earth and the Sun. And if it did, we probably would be quite aware of it already.

Tepix 8y ago

It's hard to detect dark, cold things that are far away. Planet Nine is very cold, likely to be quite dark and also very far away (anywhere between 200 AU and 1200 AU depending on where it currently is in its orbit). Its estimated apparent magnitude is greater than 22.5. That means you'll need a large telescope (I guess around 5m), a dark sky and sensitive cameras to be able to see it. Stars are neither dark nor cold, however brown dwarves that are pretty cold are much harder to detect. If you look at the list¹ of the sixty nearest stars to our sun, you'll notice that many close brown dwarves have only been found fairly recently (e.g. Luhman 16a/b, 6.5ly away were found in 2013). ¹ https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brow...