Free Astronomy Magazine September-October 2018

36 SEPTEMBER-OCTOBER 2018 SPACE CHRONICLES Supersharp images from new VLT adaptive optics by ESO T he MUSE (Multi Unit Spectroscopic Explorer) instru- ment on ESO’s Very Large Telescope (VLT) works with an adaptive optics unit called GA- LACSI. This makes use of the Laser Guide Star Fa- cility, 4LGSF, a subsys- tem of the Adaptive Optics Facility (AOF). The AOF provides adap- tive optics for instru- ments on the VLTs Unit Telescope 4 (UT4). MUSE was the first instrument to benefit from this new facility and it now has two adaptive optics modes — the Wide Field Mode and the Narrow Field Mode. The MUSE Wide Field Mode coupled to GALACSI in ground-layer mode cor- rects for the effects of atmospheric turbulence up to one kilometre above the telescope over a compar- atively wide field of view. But the new Narrow Field Mode using laser tomography corrects for almost all of the atmospheric turbu- lence above the telescope to create much sharper images, but over a smaller region of the sky. With this new capability, the 8-metre UT4 T hese images of the planet Neptune were obtained during the testing of the Narrow-Field adaptive optics mode of the MUSE/GALACSI instrument on ESO’s Very Large Telescope. The image on the right is without the adaptive optics system in operation and the one on the left after the adaptive optics are switched on. [ESO/P. Weilbacher (AIP)] reaches the theoretical limit of im- age sharpness and is no longer lim- ited by atmospheric blur. This is extremely difficult to attain in the visible and gives images comparable in sharpness to those from the NASA/ESA Hubble Space Telescope. It will enable astronomers to study in unprecedented detail fascinating objects such as supermassive black holes at the centres of distant galaxies, jets from young stars, globular clusters, supernovae, plan- ets and their satellites in the Solar System and much more. Adaptive optics is a technique to compensate for the blurring effect of the Earth’s atmosphere, also known as as- tronomical seeing, which is a big problem faced by all ground-based telescopes. The same turbulence in the atmosphere that causes stars to twinkle to the naked eye results in blurred images of the Universe for large telescopes. Light from stars and galaxies becomes distorted as it