Acknowledgement: J. Barrington
The subject of this image is NGC 6861, a galaxy discovered in 1826 by the Scottish astronomer James Dunlop.
Almost two centuries later we now know that NGC 6861 is the second
brightest member of a group of at least a dozen galaxies called the
Telescopium Group — otherwise known as the NGC 6868 Group — in the small
constellation of Telescopium (The Telescope).
This NASA/ESA Hubble Space Telescope view shows some important
details of NGC 6861. One of the most prominent features is the disc of
dark bands circling the centre of the galaxy. These dust lanes are a
result of large clouds of dust particles obscuring the light emitted by
the stars behind them.
Dust lanes are very useful for working out whether we are seeing the
galaxy disc 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 centre of the galaxy. This oval is,
rather puzzlingly, typical of an elliptical galaxy.
So which is it — spiral or elliptical? The answer is neither! NGC
6861 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.
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.
A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Josh Barrington.
