An image taken with the NASA/ESA Hubble Space Telescope
shows one of the most unusually long planetary nebulae found so far.
Scientists think planetary nebulae hold the key to understanding how
the Universe became enriched with heavier elements so they study them
intensively. It is not well-understood how a perfectly round star can
turn into such an unusual-looking nebula.

Planetary nebulae occur in a huge variety of shapes and sizes. They are
the final stage of a star’s life before it ends its days as a burnt-out
white dwarf. When it dies, a star rapidly sheds the outer parts of its
atmosphere, creating a planetary nebula that exists only as long as the
star has fuel to burn.

Witch’s cauldron

Stars are large recycling factories. Over their lifetimes of millions
of years they process huge amounts of the lighter elements (mostly
hydrogen and helium) into heavier ones (such as carbon, nitrogen and
oxygen). These heavier elements are then dispersed into the surrounding
space when the stars peel off their atmospheres to form planetary
nebulae. In turn, the heavier elements may become part of other stars
or end up in planetary systems like our own Solar System. This
dispersion process is therefore one of the most important in the
Universe and can tell us something about our own origins.

Hubble image of Henize 3-401

This image, taken with the NASA/ESA Hubble Space Telescope, shows the
young planetary nebula Henize 3-401. Hubble’s extraordinary vision
reveals that it is one of the most elongated planetary nebulae found so
far. The image shows two very long cylindrical outflows with intricate
thread-like structures and tattered ends. We are seeing the central
star responsible for the beautiful display for the first time in this

Although planetary nebulae exist in many different shapes they are
often elongated, or as astronomers call it, ‘bipolar’. Although
astronomers agree on the terminology, they disagree on how these
nebulae become so elongated. Some claim that a second star, a companion
orbiting around the central star, is needed to create the jet-like
streamers of gas. Others think that strong magnetic fields are capable
of funnelling the gas into the long outflows.

Henize 3-401 is an interesting astronomical object since astronomers
can peer directly into the brew of different elements created in the
witch’s cauldron that is a star’s core. During this brew, stars form
complex organic molecules that may be some of the molecular building
blocks of life.

Henize 3-401 is currently passing through a phase that is very short,
in astronomical terms, and there are not very many similar objects
around for similar study. It will take only a few thousand years for
the central star to exhaust its nuclear fuel and become a cooling,
fading white dwarf.

Nebula clings to its secrets

European astronomers have combined Hubble images together with
observations from several other telescopes, among them ESA’s Infrared
Space Observatory (ISO) and the International Ultraviolet Explorer
(IUE). However, it is proving difficult to unveil the origin of this
nebula. As Pedro Garcia-Lario from the ESA ISO Data Centre in
Villafranca, Spain, says: “We are studying stars at a crucial moment in
their life – as they die. Our ultimate goal is to find out exactly how
the dying stars spread these huge amounts of processed material
throughout the Universe. How can a perfectly round star undergo a rapid
metamorphosis to become such an elongated object as Henize 3-401? These
are key questions to answer if we want to find out how our Milky Way
evolves chemically.”

Despite the ongoing efforts of Garcia-Lario and others studying Henize
3-401, the detailed nature and origin of this nebula remain deep

Henize 3-401 is located in the constellation of Carina (the Keel) at an
approximate distance of 10 000 light-years. This picture is composed of
three exposures obtained with Hubble’s Wide Field Planetary Camera 2 on
12 June 1997. The three exposures were taken through a wide orange
filter (1200 seconds) shown in blue, a hydrogen-alpha filter (400
seconds) shown in red, and a singly ionised sulphur filter (1200
seconds) shown in green.

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Notes for editors

The Hubble Space Telescope project is an international cooperation
between ESA and NASA.

The original Hubble image was obtained by R. Sahai (Jet Propulsion
Laboratory, USA), V. Bujarrabal (Observatorio Astronomico, Spain), J.
Trauger (Jet Propulsion Laboratory, USA), A. Zijlstra (University of
Manchester Institute of Science and Technology, United Kingdom) and
J. Alcolea (Centro Astronomico de Yebes, Spain).

The image processing for this image was done by Richard Hook and the
Hubble European Space Agency Information Centre.

For further information please contact:

Pedro Garcia-Lario

ESA ISO Data Centre, Villafranca, Spain

Phone: +34 91 813 1389


Lars Lindberg Christensen

Hubble European Space Agency Information Centre, Garching, Germany
Phone: +49-89-3200-6306 (089 within Germany)

Cellular (24 hr): +49-173-3872-621 (0173 within Germany)