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Would it be possible to see this planet X with optical telescopes if we knew where to look at? (Assuming the figures given in article, mass 10 times earth, dist

Would it be possible to see this planet X with optical telescopes if we knew where to look at? (Assuming the figures given in article, mass 10 times earth, distance from sun 1000 times earth's distance)

mabbo 11y ago
In short, if we could it would already have a name. XKCD did a great chart to explain this potential 9th planet: https://xkcd.com/1633/ https://xkcd.com/1633/
dietrichepp 11y ago
If its mass is 10 times Earth but it has similar density, its diameter would be 10^1/3 times Earth's, or 2.75 x 10^7 m. 1000 AU is 1.50 x 10^14 m. Their ratio is equal to the angular size in radians, since atan(x) = x to within our desired precision, giving 2.75e7/1.5e14/2pi36060*60 = 0.0378 arcseconds. The Keck observatory has angular resolution of 0.04 arcseconds at best, according to Wikipedia. So, by this back of the envelope calculation, the answer is "theoretically, but probably not".
- tomr_stargazer 11y ago
  In your above calculation, you're assuming that an object needs to be resolved to be visible. To the contrary, telescopes are able to see un-resolved objects (objects whose angular size is below the angular resolution of the telescope) all the time -- they are called "stars". The relevant parameter here isn't angular size, but flux[0] (brightness). [0] https://en.wikipedia.org/wiki/Radiative_flux https://en.wikipedia.org/wiki/Radiative_flux
  - dietrichepp 11y ago
    You're absolutely right, I realized that right after I posted that.
peter303 11y ago
They have been looking for Kuiper planet X on the cover of Scientic American last year. They ruled out a gas giant planet because it would have been bright enoungh in infra red from the heat of self gravitation to already have been seen. The kuiper planet x modeling can only constraint to about a quarter of the sky, which is large search. By Keplers Law a highly elliptical planet x orbit would spend most of its time far out when itbis dimmest and slowest. This planet x could be 40 times further away than pluto where it could a thousand times dimmer and a hundred times slower motion across thevsky than hard to see pluto. The extinction planet x is even farther and slower.
pmiller2 11y ago
That would depend on the body's albedo and where it's currently located in its orbit.

mabbo 11y ago

In short, if we could it would already have a name. XKCD did a great chart to explain this potential 9th planet: https://xkcd.com/1633/ https://xkcd.com/1633/

dietrichepp 11y ago

If its mass is 10 times Earth but it has similar density, its diameter would be 10^1/3 times Earth's, or 2.75 x 10^7 m. 1000 AU is 1.50 x 10^14 m. Their ratio is equal to the angular size in radians, since atan(x) = x to within our desired precision, giving 2.75e7/1.5e14/2pi36060*60 = 0.0378 arcseconds. The Keck observatory has angular resolution of 0.04 arcseconds at best, according to Wikipedia. So, by this back of the envelope calculation, the answer is "theoretically, but probably not".

tomr_stargazer 11y ago
In your above calculation, you're assuming that an object needs to be resolved to be visible. To the contrary, telescopes are able to see un-resolved objects (objects whose angular size is below the angular resolution of the telescope) all the time -- they are called "stars". The relevant parameter here isn't angular size, but flux[0] (brightness). [0] https://en.wikipedia.org/wiki/Radiative_flux https://en.wikipedia.org/wiki/Radiative_flux
- dietrichepp 11y ago
  You're absolutely right, I realized that right after I posted that.

peter303 11y ago

They have been looking for Kuiper planet X on the cover of Scientic American last year. They ruled out a gas giant planet because it would have been bright enoungh in infra red from the heat of self gravitation to already have been seen. The kuiper planet x modeling can only constraint to about a quarter of the sky, which is large search. By Keplers Law a highly elliptical planet x orbit would spend most of its time far out when itbis dimmest and slowest. This planet x could be 40 times further away than pluto where it could a thousand times dimmer and a hundred times slower motion across thevsky than hard to see pluto. The extinction planet x is even farther and slower.

pmiller2 11y ago

That would depend on the body's albedo and where it's currently located in its orbit.