Garden-sprinkler nebula, Hen 3-1475
White Dwarfs & Planetary Nebulas
RA 17h 45m 14.20s Dec -17º 56' 47.00"
About 18,000 light years
European Space Agency, A. Riera (Universitat Politecnica de Catalunya,
Spain) and P. Garcia-Lario (ESA ISO Data Centre, Spain)
May 22, 2003
There are many mysterious
objects seen in the night sky which are not really well understood. For
example, astronomers are puzzled by the 'jets' emerging from planetary
nebulae. However, the S-shaped jet from Henize 3-1475 is the most perplexing
'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
Politecnica 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.
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.