Last Wednesday, 21st April, NASA held a press conference to unveil the first images from its Solar Dynamics Observatory (SDO) mission. The mission is the first in NASA’s Living With a Star (LWS) Program, which is designed to investigate the variability of the Sun and how it can affect life on Earth. SDO’s specific goals are to find out more about the generation and structure of the Sun’s magnetic field, and how energy from this field is released into space as the solar wind and energetic particles.
Below is one of the first images revealed from the mission. It is a full disk, multiwavelength image taken by the SDO Atmospheric Imaging Assembly (AIA). The AIA looks at the lower atmosphere of the Sun in the extreme ultraviolet region of the electromagnetic spectrum, enabling it to see hot plasma moving along magnetic field lines. False colours show variations in temperature, with reds indicating temperatures of “only” 60,000 Kelvin, with blues and greens reaching higher than one million Kelvin.
The yellowish ring shaped object in the top left hand corner of the picture above is known as a solar prominence. Another prominence spotted by SDO on 30th March can be seen below (and, if you like, you can watch a video of one here):
These prominences are large arches of dense gas that are attached to the Sun at the photosphere (where the light we receive on Earth originates from), and extend out into the corona (the Sun’s atmosphere). They appear to be very bright when viewed against the backdrop of space, but when seen on the disk of the Sun they appear dark and are known as filaments. This difference occurs because they are much cooler than the Sun’s surface, but when compared to the rest of space they are very, very hot.
Other interesting features can also be seen in pictures released last Wednesday. The picture below was taken by the Helioseismic and Magnetic Imager (HMI), and is a continuum image made up of pictures from several filters so that it closely resembles an optical image. A sunspot can be seen just above the centre of the image:
The magnetic field in a sunspot is very strong, and suppresses the transport of heat from the interior of the Sun to the surface, resulting in a cooler region that ends up looking dark as it is surrounded by much hotter material. Below is a picture taken at exactly the same time as the one above, but instead showing the Sun’s magnetic field:
The white areas in this picture have a positive magnetic field, black areas have a negative field and grey areas have zero magnetic field. It’s easy to see that the black and white region in this image corresponds to the sunspot in the previous image.
The mission was launched on 11th February this year, and is now fully operational, producing high quality images that are ten times more clear than HD television. These images will give us invaluable information about solar variations that affect life and telecommunications here on Earth, as well as the astronauts and satellites orbiting us, and will hopefully eventually enable us to better forecast the “space weather” and provide early warnings when necessary.
For more information (and lots more pretty pictures!) see the SDO website: http://sdo.gsfc.nasa.gov/firstlight/