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29

It's too dim to be seen during a normal survey during the majority of its orbit. The paper gives potential orbital parameters of $400-1500~\textrm{AU}$ for the semi major axis, and $200-300~\textrm{AU}$ for perihelion. Since the paper doesn't give a most-likely case for orbital parameters, I'm going to go with the extreme case that makes it most difficult ...


25

Brown and Batygin, the authors of the paper on the possible planet, have a webpage addressing this. A few reasons not already covered: It moves quite slowly - the authors estimate 0.2-0.6 arc seconds per hour - so standard surveys may not notice the movement and fail to recognize it as a solar system object. Eris, which is the most distant confirmed ...


19

Between $1/40,000$ and $1/8,000,000$ of the brightness as seen from Earth, depending on what the actual orbit would turn out to be, and where the planet is in its $15,000$ year orbit period. Brightness drops as $\dfrac{1}{r^2}$ with distance from the light source. Earth is at $1~\textrm{AU}.$ The theoretical planet is at $200~\textrm{AU}$ when it's closest ...


18

This graph from XKCD says a lot about why that is the case The bottom line is, the 9th planet is too small to be detected through WISE, and too far/small to have been detected through visible observation. Most likely this hypothetical planet is a long ways away, possibly as far as 1200 AU, and not particularly large, making it difficult to see. WISE was ...


16

There are many normal methods that we use to detect exoplanets, but none of them work well in the case of the 9th planet. Here are some of the main ones. Radial velocity. The Sun is not moving significantly with respect to Earth, and the hypothetical planet is too far away from the Sun to have much of an impact. Transit. This is obviously impossible, as ...


15

From an exoplanet-finding point of view, the Sun has between one and three planets. The major exoplanet-finding techniques in current use involve watching for either periodic Doppler shifts as the planet's gravitational pull causes the star to wobble, or periodic brightness shifts as the planet transits the star. Both require that the planet is large ...


10

The answer is the Coriolis effect, on Earth this produces cells within which storms move, converging towards the cell boundaries as you can see below. Jupiter however spins much faster that the Earth which produces a stronger Coriolis effect and thus more cells. This is the reason why there are so many different coloured bands on Jupiter (see image below). ...


9

If it exists, then the orbit has a perihelion of maybe 300 au and an aphelion of perhaps 2700 au. You can then just scale from the brightness $m=-26.7$ of the Sun at the Earth. It would be between 12.4 and 17.1 magnitudes fainter. So still much brighter than the next brightest star in the sky.


8

The possible planet 9 is thought to be about 10 Earth masses and is unlikely to be a gas giant (it may be the core of an "interrupted" gas giant). As such, it will not be generating significant luminosity itself and would be rocky, or more likely, icy in character. It would thus only be seen by reflected light. The considerations for what wavelength to ...


8

Those are model calculations, which hint to the existence of a possible body of about 10-times the mass of Earth. Calling this a discovery would clearly be premature. The confidence level is just a little above the "evidence" level of 3 sigma, under the assumption, that the discoveries of the KBO objects leading to the inference aren't observationally ...


8

The parallax is found from a triangle with the Earth's orbit at its base. The annual parallax here would then be between 1/200 and 1/1000 radians ($\sim$ 1000 to 200 arcseconds) which is indeed enormous and much bigger than the likely proper motion during a year.


7

Ceres is 2.76 AU away from the sun, so the sunlight is seven times weaker. That is comparable to the levels of illumination 30 minutes before sunset on Earth, so you are not going to have any problem seeing the surface. The albedo of Ceres is quite low, comparable to worn asphalt. But it is still easy to see it.


7

Planets are satellites of the Sun. Most planets have satellites. Whenever you find a parent body with satellites, you get first good results about their masses and distances by applying Kepler's laws. A second approach is using parallax measurements for distance estimates. The distance to some of the planets can be measured very accurately by radar, e.g. for ...


7

Possible reasons that the planet has not been picked up previously: It's not there. Photographic proper motion surveys cover the whoke sky. To avoid these planet 9 would have to be fainter than about 18th or 19th magnitude. This puts a lower bound in the size/albedo/distance combination for any planet 9. The proposed planet could easily be fainter than ...


7

The position of the hypothetical object is not known with any certainty, so it's hard to know where to point your telescope. The paper proposes a wide range of orbital distances anywhere from 400 to 1500 AU semi-major axis, with a perihelion (closest approach to the sun) of 200-300AU. This is 8 times as far as Neptune. (I didn't read the article closely ...


7

According to Caltech there is possibly a planet 10 times the mass of earth in a 15-20 thousand year orbit at an odd angle. It hasn't been observed yet. There's a search for it ongoing.


6

There are two basic ways to detect such an object. First is to detect it through reflected sunlight. Second is from the heat that it produces. We already know that the reflected light of such an object likely would be around a 16.5 magnitude. To determine the infrared, we have to estimate the temperature The temperature very much depends on the composition. ...


6

You are right that the tilt of the asteroids are distributed in very random way, and that the rotation of the Solar nebula is a minor contributor to that tilt, and only skews it a little. However, you are not right that randomness simply adds up. The randomness does in fact cancel out more and more when you combine a large amount of asteroids, until the ...


5

The clipping above from the Albuquerque Journal doesn't really answer your question, but astronomers have been hunting for a largeish planet beyond Pluto for quite some time now. See also: http://www.zetatalk.com/theword/tword26b.htm http://www.bibliotecapleyades.net/hercolobus/esp_hercolobus_2_02.htm (under "United States Naval Observatory ...


5

It is a planet - either a gas giant core, a mini-Neptune, or a super-Earth. First off, Mike Brown has stated outright “It is a planet—there’s virtually no doubt,” he said. “What we now call planets are objects that can gravitationally dominate their neighborhood. Pluto is a slave to the gravitational influence of Neptune. By area, Planet Nine dominates ...


5

Citing the original article: We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass $\geq \approx 10$ m⊕ whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. and As already alluded to above, the precise ...


5

We can't detect whether there are or are not objects of similar "small" sizes orbiting other stars. We simply lack that level of ability. From a scientific point of view I'd simply say "don't know". From a practical point of view I would expect other stars to have systems with a huge variety of things in orbit - there's no reason not to expect this, but ...


5

Given that Kepler has detected stars with 5 or 6 planets that exist in an extremely flattened plane and much flatter than the solar system, then we can be reasonably sure that stars with more than 4 planets are reasonably common. Given the many mechanisms for scrambling the orbital inclinations out of a perfectly flat configuration, and that seeing multiple ...


4

Direct reflection of sunlight is the most likely scenario for a ninth planet discovery, however that does not hold if the object has a very low albedo. I assume you are interested in what wavelengths the planet would radiate. For the surface temperature, the rotation of the planet is important. If it is locked with one side facing the sun, or rotates very ...


3

Maybe the Gaia space telescope has already caught it? First data release in mid-2016.


3

This question already has muliple answers on this site... However : Yes, astronomers DO have enough data to speculate about a possible Ninth Planet. The orbits of six KBO are correlated, and a possible ninth planet could be the reason for those peculiar orbits. See image below for the computed results of the possible orbit of the ninth planet.: ...


2

A consensus number is that there roughly $10^{11}$ stars in our Galaxy (though this number is certainly uncertain by a factor of at least two, because it is based on extrapolating what we know about stellar populations in our vicinity). Most of these stars are of lower mass and are much less luminous than the Sun. The number of planets is even more ...


2

Batygin and Brown made a website which describes the search for the 9th planet in clear terms. They specifically note the following: perihelion (its closest approach to the sun) at around a Right Ascension in the sky of 16 hours, which means that the perihelion position is straight overhead in late May. Conversely, the orbit comes to aphelion (the ...


2

Sorry, but none of the planets have substantial amounts of phosphorescent chemicals. Perhaps the closest to what you are thinking is the aurora, which can be seen on all the planets with atmospheres (to a greater or lesser degree) notably on the Gas Giants and on Earth. However, while the mechanism of aurora is similar to florescence, it is not ...


2

What they have at present is best described as a theory based on data that is not precise enough to make a definitive statement. They are telling people they think something is out there and roughly what they think it might be, but they really don't have accurate enough data to make any statements beyond that. The fact that the possible range of distances ...



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