SUPER-SHARP VIEW OF THE DOOMED STAR ETA CARINAE

A huge, billowing pair of gas and dust clouds are captured in this stunning NASA Hubble Space Telescope image of the supermassive star Eta Carinae.

Using a combination of image processing techniques (dithering, subsampling and deconvolution), astronomers created one of the highest resolution images of an extended object ever produced by Hubble Space Telescope. The resulting picture reveals astonishing detail.

Even though Eta Carinae is more than 8,000 light-years away, structures only 10 billion miles across (about the diameter of our solar system) can be distinguished. Dust lanes, tiny condensations, and strange radial streaks all appear with unprecedented clarity.

Eta Carinae was observed by Hubble in September 1995 with the Wide Field Planetary Camera 2 (WFPC2). Images taken through red and near-ultraviolet filters were subsequently combined to produce the color image shown. A sequence of eight exposures was necessary to cover the object's huge dynamic range: the outer ejecta blobs are 100,000 times fainter than the brilliant central star.

Eta Carinae was the site of a giant outburst about 150 years ago, when it became one of the brightest stars in the southern sky. Though the star released as much visible light as a supernova explosion, it survived the outburst. Somehow, the explosion produced two polar lobes and a large thin equatorial disk, all moving outward at about 1.5 million miles per hour.

The new observation shows that excess violet light escapes along the equatorial plane between the bipolar lobes. Apparently there is relatively little dusty debris between the lobes down by the star; most of the blue light is able to escape. The lobes, on the other hand, contain large amounts of dust which preferentially absorb blue light, causing the lobes to appear reddish.

Estimated to be 100 times more massive than our Sun, Eta Carinae may be one of the most massive stars in our Galaxy. It radiates about five million times more power than our Sun. The star remains one of the great mysteries of stellar astronomy, and the new Hubble images raise further puzzles. Eventually, this star's outburst may provide unique clues to other, more modest stellar bipolar explosions and to hydrodynamic flows from stars in general.

Photo Credit: Jon Morse (University of Colorado), and NASA

Investigating Team: Kris Davidson (University of Minnesota), Bruce Balick (University of Washington), Dennis Ebbets (Ball Aerospace), Adam Frank (University of Minnesota), Fred Hamann (University of California - San Diego), Roberta Humphreys (University of Minnesota), Sveneric Johansson (Lund Observatory), Jon Morse (University of Colorado), Nolan Walborn (Space Telescope Science Institute), Gerd Weigelt (Max Planck Inst. for Radio Astronomy, Bonn), and Richard White (Space Telescope Science Institute)

Image files in GIF and JPEG format and captions may be accessed on Internet via anonymous ftp from oposite.stsci.edu in /pubinfo. PRC96-23a Eta Carinae color gif: EtaCarC.gif jpeg: EtaCarC.jpg
Higher resolution digital versions (300dpi JPEG) of the release photographs will be available temporarily in /pubinfo/hrtemp: 96-23a.jpg (color), 96-23abw.jpg (black/white).
GIF and JPEG images, captions and press release text are available via World Wide Web at: http://www.stsci.edu/pubinfo/PR/96/23.html   and via links in: http://www.stsci.edu/pubinfo/latest.html   or http://www.stsci.edu/pubinfo/pictures.html.

This image is available on the internet at:
http://www.gsfc.nasa.gov/ftp/newsmedia/AAS/ECAR/EtaCarCl.jpg

ETA CARINAE SPECTRA

These are spectra of light emitted by hydrogen atoms in Eta Carinae and its surrounding nebula. The spectra were taken by the Space Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space Telescope. A spectrograph separates light into its component colors, which correspond to different wavelengths. This is similar to the way a prism separates white light into a rainbow of distinct colors. By analyzing light this way, astronomers learn a great deal about the object emitting the light, such as its temperature, chemical composition, and motion. The light used by STIS for this graph corresponds to hydrogen alpha emission, which appears red to the human eye.

The spectra are from different times during the star's recent doubling of brightness; December 1997 (top left), November 1998 (top right), March 1998 (bottom left), February 1999 (bottom right). The horizontal axis of each spectrum displays the wavelength, or color, of the light. Shorter wavelengths (more blue) are on the left and longer wavelengths (more red) are on the right. The vertical axis measures the brightness (intensity) of the light. The diagonal axis is the area around Eta Carinae imaged by STIS. The peak is light from Eta Carinae, and smaller peaks in the foreground are light from the surrounding nebula.

A wide "canyon" is especially prominent on the left side of the December 1997 and March 1998 spectra. This is due to the blocking of light, called an absorption feature, that probably results from an extended atmospheric "wind" of gas being blown from the surface of Eta Carinae. Note that in the spectra on the right, this canyon grows smaller and almost disappears in the February 1999 spectrum. This indicates that the wind varies with time and has recently changed substantially.

A narrow canyon can also be seen on the left side of the peaks closer to the top. This newly discovered feature indicates high density gas between the star and the observer. Its depth also changes with time. One explanation is that a rotating disk of gas surrounding Eta Carinae alternately brings high and low density regions into view, with the dense regions blocking more light when they rotate between us and Eta Carinae.

Image Credit: NASA/STScI/ Ted Gull / Phil Plait

This image is available on the internet at:
http://www.gsfc.nasa.gov/ftp/newsmedia/AAS/ECAR/all4surf_final.jpg

BRIGHTNESS GRAPH OF ETA CARINAE

This is a graph of the apparent brightness of the star Eta Carinae, from the early 1950's to 1999. Eta Carinae, a massive star famous for violent outbursts, has doubled in brightness since early 1998 and now shines more brilliantly than it has in over a century. The vertical axis represents brightness according to how bright the star appears to us on Earth, called apparent magnitude. Magnitude 6 is about the faintest that can be seen with the unaided eye. An increase in brightness is represented by smaller numbers; for example, a magnitude 5 star is about 2.5 times brighter than a magnitude 6 star.

In the 1840's, Eta Carinae flared brightly and, over a 20 year period, ejected enough material to create three Suns. The result of this eruption can be seen today as a spectacular double-lobed nebula of gas and dust, lit from within by an intemperate star. Some of the recent brightness increase may be due to the excitation of gas in the nebula by light from Eta Carinae; however, we may also be witnessing the start of another massive eruption.

Eta Carinae is about 7,500 light-years from Earth and appears in the southern sky in the constellation Carina. At about 100 times the mass of the Sun, Eta Carinae is a rare luminous blue variable star, a class that includes the brightest and most massive stars in the universe. Luminous blue variables are prone to violent displays because of their instability - they shine so brightly that their gravity can hardly hold them together.

Image credit: Kris Davidson/University of Minnesota

http://www.gsfc.nasa.gov/ftp/newsmedia/AAS/ECAR/ecar_graph.jpg

BRIGHTNESS INCREASE IN ETA CARINAE

This set of images, taken using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope, shows the recent increase in brightness of the massive, powerful star Eta Carinae. The star has doubled in brightness since early 1998, and now shines more brilliantly than it has in over a century. This is apparent when comparing the image taken in March 1998 (left) to the one taken in February 1999 (right). The brightness levels are represented by false colors, with black corresponding to no light, and white as the most intense light. The brightest areas are 1,400 times more intense than the dimmest. The images show the star and its surrounding inner nebula, out to approximately 1 trillion miles.

Image credit: NASA/STScI Ted Gull

ETA CARINAE NEBULA MODEL

This computer graphic is a model of the complex nebula surrounding the massive, powerful star Eta Carinae. The left image is a cross-section, and the right image is oriented the same way the actual nebula appears in the sky.

The yellow dot in the center is Eta Carinae, and the large, orange lobes represent the old, outer nebula surrounding the star. In the 1840's, Eta Carinae flared brightly and, over a 20 year period, ejected enough material to create three Suns. The result of this eruption can be seen today as a spectacular double-lobed nebula of gas and dust, lit from within by an intemperate star. The material at the poles (flat part of the lobe, on the top and bottom of the left image) is racing away from the star at about 600 miles per second. The material on the sides and in the interior of the lobes is not traveling so fast, which, over time, results in an elongated structure. This structure is now about one half a light year (three trillion miles) long.

The blue, cone shaped structure is a new, inner nebula, discovered using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope in March, 1998. It probably results from hot gas blowing from Eta Carinae. This stellar "wind," moving at about 180 miles per second, pushes aside slower material in the center of the old nebula. It is approximately one-tenth a light year long (600 billion miles).

The green line (green disk in the right image) is a disk of much slower gas and dust from the equator of Eta Carinae. Its uneven density is represented by pale green spokes in the right image. The disk is about one-fourth a light year across (1.5 trillion miles).

The central gray sphere corresponds to a shell of ionized gas surrounding Eta Carinae. The intense light and rapid wind from Eta Carinae removes electrons from atoms in gas close to the star, ionizing them. This region is about 100 billion miles across.

Image credit: NASA/Ted Gull, Don Lindler

GSFC Press Release 99-064