NASAさんのインスタグラム写真 - (NASAInstagram)「This was a nice catch by @NASAHubble! Hubble has a busy calendar nearly year-round, but astronomers take advantage of the gaps in the telescope’s schedule to take a look at barely observed galaxy clusters like this one! Studying these clusters can help astronomers learn more about dark matter, which makes up most of the mass of a galaxy cluster. Learn more about Hubble’s series of observations and this galaxy cluster, ACO S520, at the link in our bio! Image Description: A collection of oval-shaped, elliptical galaxies. The largest has two neighboring bright spots in the core. It and two others look like galaxy clusters, with surrounding smaller galaxies. On the left edge of the image are two bright stars with four long spikes, and on the right edge is a small ring-shaped galaxy. Smaller stars and galaxies are spread evenly across the dark background.」5月1日 23時30分