Astrophysics: Finding the best view of the sky at night

The highest ice dome on the Antarctic Plateau, Dome A, might offer the clearest view on Earth of the stars at night, suggests a paper in Nature this week.

One of the biggest challenges for Earth-based astronomy is ‘seeing’ — the effect of atmospheric turbulence on astronomical image quality; this turbulence makes stars twinkle. The best existing observatories are based in high-altitude, mid-latitude sites (Chile and Hawaiʻi), with seeing in the range of 0.6–0.8 arcseconds. The Antarctic has the potential for better seeing, owing to weaker turbulence in the free atmosphere, with an estimated range of 0.23–0.36 arcseconds at a location called Dome C.

Bin Ma and colleagues consider a different Antarctic location, Dome A, which they estimate has a thinner boundary layer (the lowest part of the atmosphere, which is influenced by the friction from the Earth’s surface) than Dome C. Previous measurements from Dome A have been taken in the daytime, but the authors report a median night-time seeing of 0.31 arcseconds, reaching as low as 0.13 arcseconds. The measurements from Dome A, taken at a height of 8 metres, were much better than those from the same height at Dome C and comparable to those at a height of 20 metres at Dome C. The thinner boundary layer above Dome A makes it less challenging to build a telescope above it, the authors propose.

Whether this extremely cold and isolated environment would be a practical site for building a telescope remains to be seen. The authors note that the viewing capabilities of their apparatus were affected by frost; overcoming this issue could potentially improve seeing by 10–12%, they suggest.

doi: 10.1038/s41586-020-2489-0

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