| Bill Stegerwald William.A.Steigerwald.1@gsfc.nasa.gov (Phone: 301-286-5017) |
Jan. 7, 1998 at 2 P.M. EST |
RELEASE NO: 98-003P
X-RAYS FROM ETA CARINAE IMAGE: This image is a composite of images made using the German/U.S./U.K. Roentgen Satellite (ROSAT) and NASA’s Hubble Space Telescope (HST). Starting from the left are two ROSAT images of X-rays from a cloud of hot gas surrounding Eta Carinae. The leftmost image was made in June of 1992, while the adjacent image was taken in August of 1994. These false color images show variations in the intensity of X-ray emission from the cloud; yellow represents areas of highest intensity while blue represents areas of lowest intensity. The image on the right is a HST image in visible light of the cloud of gas surrounding Eta Carinae. It was taken in September 1995 using the Wide Field Planetary Camera 2 instrument. The cloud of gas is the result of a massive explosion from Eta Carinae that occurred 150 years ago. Massive stars such as Eta Carinae shine so brightly that they sometimes become unstable and blow their surface layers off. This cloud of material is now about half a light year across and is expanding outward at approximately 180 miles per second. (One light year is about six trillion miles.) The white square in the August 1994 X-ray image shows the HST image to scale.
The additional yellow area in the center of the August 1994 image shows an increase in
the X-ray emission since 1992. Scientists using these images and data from NASA’s
Rossi X-ray timing Explorer (RXTE) spacecraft have discovered that the X-rays alternately
increase and decrease over time. They surmise that the changes are due to the presence of
a massive "companion" star in orbit around Eta Carinae. The light generated by
Eta Carinae is so intense that it drives hot gas away from the star’s surface,
forming a fast moving 'stellar wind' flowing into interstellar space. The same thing is
happening to the companion star orbiting Eta Carinae. Scientists believe the orbit of the
companion star is elongated into an ellipse, which alternately moves it closer to and
further away from Eta Carinae over the five and a half year orbital period. When the stars
are close, the two stellar winds slam together which creates a shock wave that heats the
gas tremendously, to about 60 million degrees, and it emits large amounts of X-rays. When
they are further away, this shock wave diminishes, along with the X-rays.
(Photo Credit: Space Telescope Science Institute and NASA Goddard Space Flight Center.)
PHOTO CREDIT: NASA, or National Aeronautics and Space Administration
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