A Trip Into a Star
Imagine a spacecraft purposefully being sent into the volatile craw of a star and expected to survive and send back data. That simplistically describes the mission of the Solar Probe Plus. This unique spacecraft will visit our nearest star—our Sun—and hopefully answer many of the questions we have about some of the strange phenomena that occur in and around it.
Plus will enter the solar corona, the outer layer of the Sun’s atmosphere, not just once, but 24 times, each time going deeper and deeper into its seething plasma. At its deepest penetration, it will come to within 8.5 solar radii of the Sun’s photosphere—the visible surface we see.
The corona extends more than 600,000 miles into space. Fortunately for Plus, it is extremely tenuous, so while its temperature in its outer reaches (its temperature increases as you go away from the photosphere—one of the mysteries Plus hopes to solve) gets to two million degrees F, the plasma is sufficiently tenuous that the engineers are certain their design will survive the journey. In such a tenuous gas, when we speak of temperature, we are speaking more of the motion of molecules than of heat as we know it.
Other mysteries scientists hope Plus will solve is the origin of the solar wind. The solar wind 'blows' out from the corona, in a torrent of electrons and other particles that sweep by Earth and flow on into interplanetary space. At times, the wind can create havoc on our planet, disrupting power grids and communications.
The wind in the corona actually comes in three sizes--slow, fast (the supersonic wind) and a wind specifically associated with Coronal Mass Ejections, much stronger than any other. It is hoped Plus will find the origins of each of these.