Discovered in 1784 by the German–British astronomer William Herschel, NGC 4394 is a barred spiral galaxy situated about 55 million light-years from Earth. The galaxy lies in the constellation of Coma Berenices (Berenice's Hair), and is considered to be a member of the Virgo Cluster.
NGC
4394 is the archetypal barred spiral galaxy, with bright spiral arms
emerging from the ends of a bar that cuts through the galaxy’s central bulge. These arms are peppered with young blue stars, dark filaments of cosmic dust, and bright, fuzzy regions of active star formation. At the centre of NGC 4394 lies a region of ionised gas known as a LINER.
LINERs are active regions that display a characteristic set of emission
lines in their spectra— mostly weakly ionised atoms of oxygen, nitrogen
and sulphur.
Although LINER galaxies are relatively
common, it’s still unclear where the energy comes from to ionise the
gas. In most cases it is thought to be the influence of a black hole at
the centre of the galaxy, but it could also be the result of a high
level of star formation. In the case of NGC 4394, it is likely that gravitational interaction
with a nearby neighbour has caused gas to flow into the galaxy’s
central region, providing a new reservoir of material to fuel the black
hole or to make new stars.
Source: ESA/Hubble - Space Telescope
