Eta Carinae is a binary system containing the most luminous and massive
star within 10,000 light-years. A long-term study led by astronomers at
NASA's Goddard Space Flight Center in Greenbelt, Maryland, combined data
from NASA satellites, ground-based observing campaigns and theoretical
modeling to produce the most comprehensive picture of Eta Carinae to
date. New findings include Hubble Space Telescope images that show
decade-old shells of ionized gas racing away from the largest star at a
million miles an hour, and new 3-D models that reveal never-before-seen
features of the stars' interactions.
Located about 7,500
light-years away in the southern constellation of Carina, Eta Carinae
comprises two massive stars whose eccentric orbits bring them unusually
close every 5.5 years. Both produce powerful gaseous outflows called
stellar winds, which enshroud the stars and stymy efforts to directly
measure their properties. Astronomers have established that the
brighter, cooler primary star has about 90 times the mass of the sun and
outshines it by 5 million times. While the properties of its smaller,
hotter companion are more contested, Goddard's Ted Gull and his
colleagues think the star has about 30 solar masses and emits a million
times the sun's light.
At closest approach, or periastron, the
stars are 140 million miles (225 million kilometers) apart, or about the
average distance between Mars and the sun. Astronomers observe dramatic
changes in the system during the months before and after periastron.
These include X-ray flares, followed by a sudden decline and eventual
recovery of X-ray emission; the disappearance and re-emergence of
structures near the stars detected at specific wavelengths of visible
light; and even a play of light and shadow as the smaller star swings
around the primary.
During the past 11 years, spanning three
periastron passages, the Goddard group has developed a model based on
routine observations of the stars using ground-based telescopes and
multiple NASA satellites. According to this model, the interaction of
the two stellar winds accounts for many of the periodic changes observed
in the system. The winds from each star have markedly different
properties: thick and slow for the primary, lean and fast for the hotter
companion. The primary's wind blows at nearly 1 million mph and is
especially dense, carrying away the equivalent mass of our sun every
thousand years. By contrast, the companion's wind carries off about 100
times less material than the primary's, but it races outward as much as
six times faster.
The images and video on this page include
periastron observations from NASA's Rossi X-ray Timing Explorer, the
X-Ray Telescope aboard NASA's Swift, the Hubble Space Telescope's STIS
instrument, and computer simulations. See the captions for details.
This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?11725
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