How is it possible that a planet can be on the other side of the sun undetected?

The new Popular Science Magazine answers the question of whether or not a planet can be hiding on the other side of the sun. While the magazine pretty much answers that if a planet does exist, it would have to be quite tiny, I don't understand how anything can exist. From what i know, planets revolve around the sun, so wouldn't any planet eventually be on our side of the sun considering they move in orbits. I mean, wouldn't anything on the "other" side of the sun eventually end up on "our" side of the sun.How is it possible that a planet can be on the other side of the sun undetected?
This isn't possible. Such a planet could theoretically exist however it would have to be at exactly the same distance from the Sun as the Earth for it to remain permanently hidden. However, we know another planet can't be there because Cruithne is in the same orbit as the Earth and exhibits a "horseshoe" orbit. This means that it passes through the area of space where the other planet would be every couple of hundred years, even as all three bodies continue their orbits around the Sun.
Yes but astronomers hate waiting ;)How is it possible that a planet can be on the other side of the sun undetected?
Remember, the Earth is moving too. So when someone claims there's a planet on the other side of the Sun, what they're saying is that it has the same orbital period as us, so it's always on the other side of the Sun from our point of view. There could be asteroids like this, but anything planet-size or larger would show up in how it effected other solar system bodies.How is it possible that a planet can be on the other side of the sun undetected?
Even if the extreme remote possibility that it were hidden, we have SOHO orbiting the sun including the other side of it. We would know it if there was one there.
If the planet is near out orbit, they're saying the planet stays on the other side of the sun due to its similar orbital speed to us, and therefore is undetectable through the suns radiation. They could also be saying that an extrasolar planet, one large enough to be considered a planet past the orbit of Neptune, is generally on the other side of the sun and hasn't been detected.
It would have to have exactly the same orbit in terms of distance from the sun, eccentricty, and tilt of it's orbit. At the same time it would have to have been created at exactly 180 degrees from the position of Earth.



All this is possible, though extremely unlikely. However, it's gravitational effect would have been detected many years ago, by pertubations of the orbits of interplanetary craft, and on the orbits of Venus and Mars.



Moreover, both those planets (as well as Jupiter) would have perturbed the orbit of the object through time, so at some point it would have been detected. So, rest assured such a planet does not exist.
There can't be such a planet of any significant size. Why not? Because Earth's orbit isn't circular. Because of that, any planet on the opposite side of the sun, even one having the same orbital semimajor axis as Earth does, and regardless of what its orbital eccentricity is, will at some point in its orbit become angularly separated from the sun, as viewed from Earth, and thus subject to being seen by people who study the solar corona while keeping the sun's disk occluded.
well yes, unless it has the same orbit as earth does. in which case it would always be between us and the sun.



but nothing of the sort exists, satellites and space probes would have directly seen it. not to mention the gravitational disturbances it would cause.
It is pretty impossible.