The corona of an active region adjacent to a coronal hole, seen by Hinode (credit: NAOJ/JAXA/NASA/STFC/ESA)
The Sun's hot secrets
With the invention of the telescope at the beginning of the seventeenth century, Galileo discovered Saturn’s rings, sunspots on the sun, and craters on the moon. Today, advances in technology are still crucial to the discovery process. Advanced telescopes onboard the Japanese satellite Hinode show the Sun in unprecedented detail, revealing processes on the Sun never seen before.
Hinode – meaning ‘sunrise’ in Japanese – was launched to study magnetic fields on the Sun and how they heat up the corona and drive eruptions, such as solar flares. Despite decades of research, many aspects of solar flares are still not well understood, but predicting them would be invaluable since they damage satellites and pose a radiation hazard to astronauts.
Using Hinode’s Extreme Ultraviolet Imaging Spectrometer (EIS) scientists have pinpointed the source of plasma that streams from the Sun during a solar flare. Solar flares can impact a vast area on the Sun, sometime leaving behind mysterious dark patches that are up to twenty times the diameter of the Earth. By training the EIS on the material in these dark patches, the mission teams saw material flowing from a dark patch in the wake of a solar flare, amplifying it as it fires plasma into the solar system at 2000 times the speed of a jet plane.
Another long-standing mystery of our nearest star is the corona. This is the outer stratum of solar atmosphere and is much hotter than its visible surface, the photosphere. The exact mechanism that heats the corona is still unclear, but it seems to rely on the magnetic field of the Sun. Strongest concentrations of magnetic field form dark areas called sunspots; and magnetic fields connecting pairs of sunspots arch above the photosphere through the corona, developing bright arcades, called coronal loops.
Scientists are using Hinode to study coronal loops in detail, and have seen turbulence within them that may be key to the coronal heating mechanism. The mission teams were surprised and excited to see that not all the action takes place inside the intense loops as expected, but in the less energetic, harder to see areas surrounding the loops.
Hinode is operated by Japan in partnership with the USA and the UK, in co-operation with the European Space Agency and the Norwegian Space Centre.
Find our more about Hinode by clicking on the link below.
