ESO Press Photos 34a-h/04

The Tarantula Nebula is one of the most impressive views in the Southern
sky, cf. ESO Press Photos 14a-g/02. Visible to the unaided eye in the
Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way that is
located in the direction of the southern constellation Doradus at a
distance of about 170,000 light-years, this huge nebula is the prototype
of what astronomers refer to as a “Giant HII region”. In this complex of
glowing gas and very hot and luminous stars, the gas is mainly composed of
protons and electrons, which are kept apart by energetic photons emitted
by the stars in this area.

The Tarantula Nebula (also designated 30 Doradus) owes its name to the
arrangement of its brightest patches of nebulosity that somewhat
resemble the legs of a spider. They extend from a central “body” where
a cluster of hot stars (designated “R136”) resides that illuminate the
nebula. This name, of the biggest spiders on the Earth, is also very
fitting in view of the gigantic proportions of the celestial nebula –
it measures nearly 1,000 light years across!

While the central regions of 30 Doradus may be compared to a tarantula,
the entangled filaments in the outskirts of this nebula – some of which
are seen in PR Photo 34a/04, obtained with the WFI camera at the ESO/MPG
2.2-m telescope at the La Silla Observatory – could well be likened with
its cobweb. They testify to an ongoing history of very vigorous activity
and make this spectacular sky region a showcase of dramatic effects caused
by the tremendous output of energy from the most massive stars known.

Intricate colours

The marvellous richness of the filament colours is due to the varying
conditions in the interstellar gas in this region, cf. PR Photo
34b/04. The red in these images is caused by emission of excited
hydrogen atoms, the green shades correspond to emission from oxygen
atoms from which two electrons (“doubly-ionized oxygen”) have been
“knocked off” by the energetic radiation of hot stars in the R136
cluster, that is located beyond the lower right corner of this photo. The
intensity of this emission increases towards R136, explaining the
yellowish colour near the edge of the photo. A blue colour is contributed
by singly-ionized atoms of oxygen.

Other atoms like nitrogen and sulfur at different levels of ionization
also add to the emission of the nebula at specific wavelengths. The
observed colours thus probe the physical condition of the emitting gas
and the temperature of the star(s) that excite(s) it. The intricate
appearance of the filaments is mostly a consequence of turbulence in
the interstellar gas, of the magnetic fields, and of the energy input
by the massive stars in the neighbourhood.

Supernovae blow interstellar “bubbles”

The large ring-shaped nebula slightly to the lower-left (South-East) of
the centre of PR Photo 34a/04 is known as DEM L 299 [1]. Detailed
investigations show that it represents an “interstellar bubble” which
was “blown” by supernovae explosions, most probably happening millions
of years ago, as massive stars near the centre of this structure ended
their comparatively short lives in glorious flashes.

A closer inspection shows that another supernova exploded somewhat
later near the rim, forming a bright and more compact nebula known as
SNR 0543-689 (PR Photo 34c/04). Other supernovae in this general field
exploded even more recently, such as the one that created the remnant
B0544-6910 (PR Photo 34d/04) only a few tens of thousands of years
ago, a blink of an eye by all astronomical standards.

Nebulae with built-in powerhouses

Not all the nebulae seen in this region are caused by supernovae, however.
The glow of N 164 [1], a bright, extended red-yellow nebula just below DEM
L 299, is mostly due to its own “private” powerhouse, that consists of
several massive stars deeply embedded in its interior (PR Photo 34e/04).

The same holds for DEM L 297, the somewhat smaller and fainter nebula to
the right of DEM L 299 (PR Photo 34f/04). It is divided into two
half-circle formed segments by a dark lane of interstellar dust in front
of it. Indeed, within the Tarantula complex many such dark and dusty
clouds are seen in silhouette as they obscure bright nebulosity behind

Many stellar clusters

The outskirts of the Tarantula Nebula are also rich in stellar clusters.
One of them, NGC 2093 [1], cf. PR Photo 34g/04, has relatively few stars
and is relatively young, just a few tens of millions of years. It appears
that its stars have already excavated a sizeable cavity around them that
is now relatively void of gas.

An older and much more compact cluster, NGC 2108, is seen near the bottom
of PR Photo 34a/04 and reproduced in full in PR Photo 34a/04. It resembles
the globular clusters in our own Galaxy, but it formed much more recently,
about 600 million years ago. Still, NGC 2108 is much older than the
Tarantula complex and it is quite possible that in its “youth” it was the
core of another giant HII region that has since dissolved into nterstellar

The images for this release were produced by two ESO astronomers who are
impressed by this sky region. Nausicaa Delmotte did the observations for
her thesis and notes that: “many of the nebulae and clusters seen in these
photos would stand out prominently if they were located elsewhere in the
sky and not this close to the core of the spectacular Tarantula complex.”.
She is echoed by her colleague, Fernando Comeron: “This amazing
concentration of clusters, HII regions, supernova remnants, and extremely
hot and luminous stars in a single region makes the Tarantula in the LMC a
unique celestial object, unrivalled in our own Galaxy and other nearby

The full text of this ESO PR Photo Release, with eight images and all
weblinks, is available at:


[1]: The designation “DEM L 299” indicates that this object is no. 299 in
the list of nebulae in the Large and Small Magellanic Clouds published in
1976 by astronomers R.D.Davies, K.H.Elliott and J.Meaburn. “N” refers to
a list of bright nebulae in these galaxies that was compiled in 1956 by
K.G.Henize. “NGC” stands for the “New General Catalogue” published in 1888
by J.L.E. Dreyer.