Astronomers at Big Bear Solar Observatory in sunny California have upgraded their 1.6-meter telescope with a new adaptive optics system. The scope is now producing the highest-resolution images ever taken of the Sun.

The Big Bear Solar Observatory recently upgraded its New Solar Telescope with an advanced adaptive optics system. Now the telescope is showing a sharper-than-ever view of the Sun.

The telescope cuts through the blurring effects of Earth’s atmosphere by sending light from its 1.6-meter primary mirror into a deformable mirror only the size of a fist. The mirror bends and twists hundreds of times every second to respond to changes in the atmosphere. Small-scale features on the Sun are used as the telescope's "guide stars" — the camera that detects distortions in the atmosphere takes 1,500 frames a second, so a solar feature that lasts for even 10 minutes might as well be immortal for the purpose of adaptive optics, says Philip Goode, director of the Big Bear Solar Observatory.

There used to be 97 actuators guiding its movement — now it has 357. With the new system, the telescope will resolve down to 0.05 arcsecond even at the bluest wavelengths, where light is the most difficult to focus. That means the telescope can resolve solar features just twice the size of Manhattan.

The images below are the telescope’s “engineering first light” — the first light seen by the telescope as the higher-order adaptive optics undergoes testing. The testing should be complete by October.

Already, the system is producing some of the sharpest pictures ever taken of the Sun’s visible surface. The images reveal fine details in sunspot structure.


From left to right:

1. The arrow points to light-colored dots in the dark center of the sunspot. Some of these dots look like coffee beans: two elongated bright kernels separated by a thin dark line
.



2. The arrow points to dark channels of filaments
crossing through a sunspot’s light-colored outer edge.



3. The circle highlights a bright, bow-shaped ridge surrounding a somewhat darker area with a bright straight
lane. Magnetic field lines are likely emerging from this feature.



4. The arrow points to an elongated bright point, which is likely a highly inclined tube of magnetic flux.



5. The arrow points to the center of a small micro-pore, where the strong magnetic fields between granules meet.



6. The circle highlights a larger, daisy shaped micro-pore.

Another image taken two days later shows that the same sunspot has developed a penumbra, the lighter-colored edge. The boiling motion of solar plasma, known as granulation, is clearly visible in both images.