Not so long ago, the real nature of the “spiral nebulae”,
spiral-shaped objects observed in the sky through telescopes, was
still unknown. This long-standing issue was finally settled in 1924
when the famous American astronomer Edwin Hubble provided conclusive
evidence that they are located outside our own galaxy and are in fact
“island universes” of their own.
Nowadays, we know that the Milky Way is just one of billions of
galaxies in the Universe. They come in vastly different shapes –
spiral, elliptical, irregular – and many of them are simply beautiful,
especially the spiral ones.
Astronomers Mark Neeser from the Universitats-Sternwarte Munchen
(Germany) and Peter Barthel from the Kapteyn Institute in Groningen
(The Netherlands) were clearly not insensitive to this when they
obtained images of three beautiful spiral galaxies with ESO’s Very
Large Telescope (VLT). They did this in twilight during the early
morning when they had to stop their normal observing programme,
searching for very distant and faint quasars.
The resulting colour images (ESO PR Photos 33a-c/03) were produced by
combining several CCD images in three different wavebands from the
FORS multi-mode instruments.
The three galaxies are known as NGC 613, NGC 1792 and NGC 3627. They
are characterized by strong far-infrared, as well as radio emission,
indicative of substantial ongoing star-formation activity. Indeed,
these images all display prominent dust as well as features related to
young stars, clear signs of intensive star-formation.
The full text of ESO PR Photos 34a-c/03, with three photos and all
weblinks, is available at:
http://www.eso.org/outreach/press-rel/pr-2003/phot-33-03.html
NGC 613
NGC 613 is a beautiful barred spiral galaxy in the southern
constellation Sculptor. This galaxy is inclined by 32 degrees and,
contrary to most barred spirals, has many arms that give it a
tentacular appearance.
Prominent dust lanes are visible along the large-scale bar. Extensive
star-formation occurs in this area, at the ends of the bar, and also
in the nuclear regions of the galaxy. The gas at the centre, as well
as the radio properties are indicative of the presence of a massive
black hole in the centre of NGC 613.
NGC 1792
NGC 1792 is located in the southern constellation Columba (The Dove) –
almost on the border with the constellation Caelum (The Graving Tool)
– and is a so-called starburst spiral galaxy. Its optical appearance
is quite chaotic, due to the patchy distribution of dust throughout
the disc of this galaxy. It is very rich in neutral hydrogen gas –
fuel for the formation of new stars – and is indeed rapidly forming
such stars. The galaxy is characterized by unusually luminous
far-infrared radiation; this is due to dust heated by young stars.
The third galaxy is NGC 3627, also known as Messier 66, i.e. it is the
66th object in the famous catalogue of nebulae by French astronomer
Charles Messier (1730 – 1817). It is located in the constellation Leo
(The Lion).
NGC 3627 is a beautiful spiral with a well-developed central bulge. It
also displays large-scale dust lanes. Many regions of warm hydrogen
gas are seen throughout the disc of this galaxy. The latter regions
are being ionised by radiation from clusters of newborn stars. Very
active star-formation is most likely also occurring in the nuclear
regions of NGC 3627.
The galaxy forms, together with its neighbours M 65 and NGC 3628, the
so-called “Leo Triplet”; they are located at a distance of about 35
million light-years. M 66 is the largest of the three. Its spiral arms
appear distorted and displaced above the main plane of the galaxy. The
asymmetric appearance is most likely due to gravitational interaction
with its neighbours.
