The sun might seem like a pretty huge galactic blind spot, but we've already managed to glimpse behind it, and there's nothing there in the way of another Earth, says NASA scientist Michael Kaiser, "unless it's awfully tiny."
Kaiser is the project scientist for NASA's Solar Terrestrial Relations Observatory (STEREO) mission, which in 2006 sent two golf-cart-size satellites into orbit around the sun to study the explosions on the solar surface that are a major factor in space weather. A few months after their launch, the two probes were angled such that they could see beyond the sun, but they found no planets lurking behind the big star.
Even if we couldn't see behind the sun, the gravitational pull of a roughly 100-mile-wide planet hiding there would noticeably affect the orbits of the other planets. And if astronomers had somehow missed that detail, Kaiser says, an unaccounted-for tug of gravity in the solar system would have disrupted the orbit of man-made satellites circling the Earth or interfered with intra-solar-system spacecraft. That hasn't happened, so unless beings on a hidden planet have invented both an invisibility cloak and a gravity-masking device, the other side of the sun is almost certainly just empty space.
I never actually thought of that. You always hear people talking about the 'dark side of the moon' i.e. the part we never see from Earth, but the sun's a different matter entirely. Pretty intersting
There's been quite a few media-hype style titles from popsci. Please slow it down a little, as you're distancing yourself from objectivity. "Could There Be a Planet Hidden on the Opposite Side of our Sun?", would be much better written as "There Is No Planet Hidden on the Opposite Side of our Sun." since the article isn't about the question, but about the answer.
A previous gem includes "Armageddon For Real", which wasn't at all "for real". It was at best a simple proposition without any real planning or monetary backing.