NASAのインスタグラム(nasa) - 1月18日 09時14分

So which is it — spiral or elliptical? The answer is neither! NGC 6861, a galaxy discovered in 1826 by the Scottish astronomer James Dunlop, does not belong to either the spiral or the elliptical family of galaxies. It is a lenticular galaxy, a family which has features of both spirals and ellipticals.

Dust lanes are very useful for working out whether we are seeing the galaxy disk edge-on, face-on or, as is the case for NGC 6861, somewhat in the middle. Dust lanes like these are typical of a spiral galaxy. The dust lanes are embedded in a white oval shape, which is made up of huge numbers of stars orbiting the center of the galaxy. This oval is, rather puzzlingly, typical of an elliptical galaxy. The relationships between these three kinds of galaxies are not yet well understood. A lenticular galaxy could be a faded spiral that has run out of gas and lost its arms, or the result of two galaxies merging. Being part of a group increases the chances for galactic mergers, so this could be the case for NGC 6861, which is in the small constellation of Telescopium (The Telescope).. Image credit: ESA/Hubble & NASA; acknowledgement: J. Barrington

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