The third
81. way
of galaxies
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.
This 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.
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.
Credit: ESA/Hubble & NASA
Pillars
82. of
Creation
These columns that resemble stalagmites
protruding from the floor of a cavern
columns are in fact cool interstellar
hydrogen gas and dust that act as
incubators for new stars. Inside them and
on their surface astronomers have found
knots or globules of denser gas. These are
called EGGs (acronym for “Evaporating
Gaseous Globules”). Inside at least some
of the EGGs stars being formed.
Undersea coral? Enchanted castles?
Space serpents? These eerie, dark pillarlike structures are actually columns of
cool interstellar hydrogen gas and dust
that are also incubators for new stars. The
pillars protrude from the interior wall of
a dark molecular cloud like stalagmites
from the floor of a cavern.
Credit: Jeff Hester and Paul Scowen
(Arizona State University), and
NASA/ESA