Q+A CENTER

Everyone remembers the lesson from school: the sun is 149.6 million kilometers (93 million miles) from earth. We know it’s hot (5,500° C or about 9,900° F on the surface, while at the core it’s something on the order of 15 million° C or 27 million° F), almost perfectly round, dense (its mass is almost 330,000 times that of Earth), and about 73 percent hydrogen, 25 percent helium and 2 percent other gasses. And we know that without it, life on earth would cease to exist.

So, what more do we need to know? That’s the job of NASA’s Solar Dynamics Observatory (SDO). Imaging will play a major role as the SDO studies how solar activity is created and how space weather results from that activity. NASA says it will measure the sun’s interior, magnetic field, the hot plasma of the solar corona, and the irradiance.

SDO is one of two groups of mission spacecraft in NASA’s Living With a Star (LWS) program. The other is Geospace Missions Network, consisting of spacecraft in the magnetosphere and ionosphere to define the Geospace response to solar and solar wind input.

Solar wind is a continuous stream of plasma. In addition, the sun periodically releases billions of tons of matter in what are called coronal mass ejections. These are immense clouds of material that, when directed towards earth, can cause large magnetic storms in the magnetosphere and the upper atmosphere. Magnetic storms cause many noticeable effects on and near earth. They include the Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights); communications disruptions, radiation hazards to orbiting astronauts and spacecraft; current surges in power lines; orbital degradation; and corrosion in oil pipelines.

“SDO will improve our understanding of the physics behind the activity displayed by the sun’s atmosphere, which drives space weather in the heliosphere, the region of the sun’s influence, and in planetary environments,” according to a NASA mission guide. “SDO will determine how the sun’s magnetic field is generated, structured and converted into violent solar events that cause space weather. SDO observations start in the interior of the sun where the magnetic field that is the drive for space weather is created. Next, SDO will observe the solar surface to directly measure the magnetic field and the solar atmosphere to understand how magnetic energy is linked to the interior and converted to space weather causing events. Finally, SDO will measure the extreme ultraviolet irradiance of the sun that is a key driver to the structure and composition of the earth’s upper atmosphere.”