Violent Outbursts in Eta Carinae
HUBBLE OBSERVES A STAR ON THE BRINK OF DESTRUCTION
A NASA Hubble Space Telescope "natural color" image of the
material surrounding the star Eta Carinae, as imaged by the Wide
Field Planetary Camera 2 (WFPC-2).
The Camera was installed in the Hubble Space Telescope during the
STS-61 Hubble Servicing Mission. The WFPC-2 optically corrects
for the aberration of the telescope's primary mirror, restoring
the telescope's vision to its originally planned clarity.
Eta Carinae has a mass of approximately 150 times that of the
sun, and is about 4 million times brighter than our local star,
making it one of the most massive and most luminous stars known.
Eta Carinae is highly unstable, and prone to violent outbursts.
The last of these occurred in 1841, when despite its distance
(over 10,000 light years away) Eta Carinae briefly became the
second brightest star in the sky.
Pre-servicing mission HST observations taken with the WF/PC-I
reveled new detail in the rapidly expanding shell of material
which was ejected during the last century's outburst. However,
the earlier effects of HST's spherical aberration obscured the
structure of the material very near Eta Carinae itself.
The clear view of Eta Carinae now provided by WFPC-2 dramatically
demonstrates the ability of HST to reliable study faint structure
near bright objects.
The picture is a combination of three different images taken in
red, green, and blue light. The ghostly red outer glow
surrounding the star is composed of the very fastest moving of
the material which was ejected during the last century's
outburst. This material, much of which is moving more than two
million miles per hour, is largely composed of nitrogen and other
elements formed in the interior of the massive star, and
subsequently ejected into interstellar space.
The bright blue-white nebulosity closer in to the star also
consists of ejected stellar material. Unlike the outer
nebulosity, this material is very dusty and reflects starlight.
The new data show that this structure consists of two lobes of
material, one of which (lower left) is moving toward us and the
other of which (upper right) is moving away. The knots of
ejected material have sizes comparable to that of our solar
Previous models of such bipolar flows predict a dense disk
surrounding the star which funnels the ejected material out of
the poles of the system. In Eta Carinae, however, high velocity
material is spraying out in the same plane as the hypothetical
disk, which is supposed to be channeling the flow.
This is quite unexpected. The WFPC-2 observations of Eta Carinae
raise as many questions as they answer.
credit: J. Hester/Arizona State University
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