'Jets' are long outflows of fast-moving gas
found near many objects in the Universe, such as around young stars,
or coming from black holes, neutron stars, and planetary nebulae,
for example. The NASA/ESA Hubble Space Telescope has imaged the
young planetary nebula Henize 3-1475 and its bizarre jet.
Astronomers have nicknamed it the 'Garden-sprinkler' Nebula.
The origin of jets in the Universe is unclear, but they appear to
originate in small regions of space where even Hubble's sharp vision
cannot penetrate. To produce a jet, you require some sort of nozzle
mechanism. So far, these theoretical 'nozzles' remain hidden by dust
that obscures our view of the centres of planetary nebulae.
Despite decades of intense effort, there is no single example of
a jet whose origin is clearly understood. The curious S-shape and
extreme high speed of its gaseous outflow gives Henize 3-1475 a
special place in the study of planetary nebulae.
Henize 3-1475 is located in the constellation of Sagittarius
around 18 000 light-years away from us. The central star is
more than 12 000 times as luminous as our Sun and weighs three
to five times as much. With a velocity of around 4 million
kilometres per hour, the jets are the fastest ever discovered.
Scientists are also intrigued by the converging, funnel-shaped
structures that connect the innermost 'knots' and the core region.
A group of international astronomers led by Angels Riera from
Universitat Politècnica de Catalunya, Barcelona, Spain, have
combined observations from Hubble's Wide Field and Planetary
Camera 2, the Space Telescope Imaging Spectrograph and
ground-based telescopes. Their work suggests that the nebula's
S-shape and hypervelocity outflow is created by a central source
that ejects streams of gas in opposite directions and precesses once
every 1500 years. It is like an enormous, slowly rotating garden
sprinkler.
The flow is not smooth, but rather episodic with an interval of
about 100 years, creating clumps of gas moving away at velocities up
to 4 million kilometres per hour. The reason for these intermittent
ejections of gas is not known. It may be due to either cyclic
magnetic processes in the central star (similar to the Sun's 22-year
magnetic cycle), or to interactions with a companion star.
For
broadcasters, animations of Henize 3-1475 are available from http://www.spacetelescope.org/video/heic0308_vnr.html
More info about Henize 3-1475
The colour image is composed of five different exposures with
Hubble's Wide Field and Planetary Camera 2 through the
following filters: a wide blue filter (500 seconds), oxygen (800
seconds) shown in green, hydrogen-alpha (830 seconds) shown in
yellow-orange, a singly ionised sulphur filter (1200 seconds) shown
in orange-red and a wide red filter shown in red.
The composite image was constructed with data from the ESO/ST-ECF
Science Archive. The original Hubble exposures were obtained by J.
Borkowski, (North Carolina State University, United States), J.
Harrington, (University of Maryland, United States), J. Blondin
(North Carolina State University, United States), M. Bobrowsky
(Challenger Center for Space Science, United States), M. Meixner
(Space Telescope Science Institute, United States), and C. Skinner
(Space Telescope Science Institute, United States).
The Hubble Space Telescope is a project of international
cooperation between ESA and NASA.
Angels
Riera
Universitat Politècnica de Catalunya
Barcelona,
Spain
Tel. +34 93 896 77 39 (Monday, Wednesday, Thursday)
Tel.
+34 93 402 11 27 (Tuesday and Friday)
E-mail: angels.riera@upc.es
Pedro García-Lario
European Space Agency ISO Data
Centre
Villafranca, Spain
Phone: +34 91 813 1389
E-mail: pedro.garcia.lario@esa.int
Lars Lindberg Christensen
Hubble European Space Agency
Information Centre
Garching, Germany
Tel: +49 89 3200 6306
(089 within Germany)
Cellular (24 hr): +49 173 3872 621 (0173
within Germany)
E-mail: lars@eso.org