Hi Lauren,
I think to say that the magnetic field controls the planets might be a bit strong, but it certainly effects them.
Magnetic fields were first discovered on the Sun around 1907-1908 by George Hale who measured the magnetic field in sunspots at Mt. Wilson Observatory (see http://physics1.usc.edu/solar/history.html). Understanding how the solar magnetic field and related things like the solar wind, flares, and coronal mass ejections effect Earth and other planets has been a long journey, though, and we are still working on it.

best,
Terry

Hi Lauren,

One thing that the Sun's magnetic field does do is create a bubble which contains our planets (and more). This is called the Heliosphere and it extends out to where the pressure from the Sun's magnetic field and solar wind balance the pressure from the magnetic field and material in the Interstellar Medium (what we call the space between the star systems). This boundary moves around a bit, but is beyond 100 AU (where 1 AU is the distance of the Sun to the Earth or 93 million miles).

The two Voyager spacecraft are the only ones to get out this far and actually exit the Heliosphere and move into Interstellar Space. When Voyager 1 first did this in 2012, what it saw was not what scientists expected! Even with Voyager 2 going out last year, there are things we don't completely understand. So we are still working on understanding how the Sun's magnetic field shapes the space we live in (even very, very far from Earth).