Twin spacecraft take first 3D images of the Sun
Apr 24, 2007
The first 3D images of the Sun have been released by NASA. Taken by its twin STEREO spacecraft, which were launched in October 2006, the images should allow astronomers to gain a better understanding of coronal mass ejections (CMEs). These enormous explosions on the surface of the Sun can eject billions of tonnes of plasma into space at millions of kilometres per hour, potentially wiping out electrical grids on the Earth and damaging orbiting satellites.
The twin satellites of NASA's $540m Solar Terrestrial Relations Observatory (STEREO) orbit the Sun with one slightly ahead of Earth and the other slightly behind. The 3D images are created by virtue of the satellites being slightly separated in space -- just as a pair of eyes can perceive depth. The new images released by NASA cover all wavelengths detected by STEREO (visible, ultraviolet and radio) and some clearly show plumes of material emanating from the surface of the Sun (see figure "3D plumes").
CMEs can send electrical currents and high-energy particles coursing through the Earth's protective magnetic field. The resulting geomagnetic storms can cause severe disruption by knocking out power grids and telecommunications systems. It is hoped that the STEREO satellites will transform our understanding of why CMEs occur and also allow scientists to better forecast when geomagnetic storms will happen.
NASA's existing Advanced Composition Explorer satellite (ACE) can warn of a geomagnetic storm about an hour before it strikes. STEREO is expected to increase this notice period to about two days. STEREO's satellites contains nearly identical suites of visible, ultraviolet and radio detectors to track the direction and speed of CMEs from their origin at the solar surface, through the Sun's atmosphere and then across the interplanetary medium.
About the author
Hamish Johnston is editor of Physics Web