Quite a few of the most beautiful objects in the Universe are still
shrouded in mystery. Even though most of the nebulae of gas and dust
in our vicinity are now rather well understood, there are some which
continue to puzzle astronomers.

This is the case of a small number of unusual nebulae that appear to
be the subject of strong heating – in astronomical terminology, they
present an amazingly “high degree of excitation”. This is because they
contain significant amounts of ions, i.e., atoms that have lost one or
more of their electrons. Depending on the atoms involved and the
number of electrons lost, this process bears witness to the strength
of the radiation or to the impact of energetic particles.

But what are the sources of that excitation? Could it be energetic
stars or perhaps some kind of exotic objects inside these nebulae? How
do these peculiar objects fit into the current picture of universal
evolution?

New observations of a number of such unusual nebulae have recently
been obtained with the Very Large Telescope (VLT) at the ESO Paranal
Observatory (Chile). In a dedicated search for the origin of their
individual characteristics, a team of astronomers – mostly from the
Institute of Astrophysics & Geophysics in Liege (Belgium) [1] – have
secured the first detailed, highly revealing images of four highly
ionized nebulae in the Magellanic Clouds, two small satellite galaxies
of our home galaxy, the Milky Way, only a few hundred thousand
light-years away.

In three nebulae, they succeeded in identifying the sources of
energetic radiation and to eludicate their exceptional properties:
some of the hottest, most massive stars ever seen, some of which are
double.

With masses of more than 20 times that of the Sun and surface
temperatures above 90 000 degrees, these stars are truly extreme.

More information
The full text of this ESO Press Release, with four spectacular images
and a detailed explanation of the scientific method behind this work,
is available at:

http://www.eso.org/outreach/press-rel/pr-2003/pr-08-03.html

The information contained in this press release is based on two
research articles to be published in the European research journal
“Astronomy & Astrophysics”, one of which is available at the preprint
website at the Institut d’Astrophysique et de G=E9ophysique de Li=E8ge
(Belgium).

Note
[1]: The team consists of Yael Naze, Gregor Rauw, Jean Manfroid and
Jean-Marie Vreux (Liege Institute, Belgium), and You-Hua Chu
(University of Illinois, USA).

Contact

Yael Naze
Institut d’Astrophysique et de Geophysique
Liege, Belgium
Phone: +32 4 366 97 20
email: naze@astro.ulg.ac.be