The object shown in these NASA/ESA Hubble Space Telescope images is aremarkable example of a star going through death throes just as itdramatically transforms itself from a normal red giant star into aplanetary nebula. This process happens so quickly that such objects arequite rare, even though astronomers believe that most stars like theSun will eventually go through such a phase.
This star, with the prosaic name of OH231.8+4.2, is seen in theseinfrared pictures blowing out gas and dust in two opposite directions.So much dust has been cast off and now surrounds the star that itcannot be seen directly, only its starlight that is reflected off thedust. The flow of gas is very fast, with a velocity up to 450,000 mph(700,000 km/h). With extreme clarity, these Hubble Near Infrared Cameraand Multi-Object Spectrometer (NICMOS) images reveal that thefast-moving gas and dust are being collimated into several thinstreamers (on the right) and a jet-like structure (on the left), whichcan be seen extending away from the centers of both pictures. On theright, wisps of material in jet-like streamers appear to strike somedense blobs of gas. This interaction must produce strong shock waves inthe gas.
The pictures represent two views of the object. The color image is acomposite of four images taken with different NICMOS infrared filterson March 28, 1998. It shows that the physical properties of thematerial, both composition and temperature, vary significantlythroughout the outflowing material. The black-and-white image was takenwith one NICMOS infrared filter. That image is able to show moreclearly the faint detail and structure in the nebula than can beachieved with the color composites.
Observations by radio astronomers have found many unusual molecules inthe gas around this star, including many containing sulfur, such ashydrogen sulfide and sulfur dioxide. These sulfur compounds arebelieved to be produced in the shock waves passing through the gas.Because of the large amount of sulfur compounds, this object has earnedthe nickname "The Rotten Egg" Nebula. It resides in the constellationPuppis.
These NICMOS data pose a serious challenge to astrophysical theorists:How can a star generate such tightly collimated streams of gas anddust and accelerate them to such very high velocities? William B.Latter from the California Institute of Technology and his group areusing these data to obtain a better understanding of the detailedstructure in the outflowing material, look for evidence for the originof the thin streamers and jets, and learn more about the star itself.This information will give astronomers a more complete understanding ofthe final stages in the lives of stars like our Sun.
These results were presented at the "Asymmetrical Planetary NebulaeII: From Origins to Microstructures" conference on Aug. 3 to 6, 1999at the Massachusetts Institute of Technology. The results also will bepublished in the Astrophysical Journal.
Credit: NASA, ESA, William B. Latter (SIRTF Science Center/CaliforniaInstitute of Technology), John H. Bieging (University of Arizona),Casey Meakin (University of Arizona), A.G.G.M. Tielens (KapteynAstronomical Institute), Aditya Dayal (IPAC/NASA Jet PropulsionLaboratory), Joseph L. Hora (Center for Astrophysics), and Douglas M.Kelly (University of Arizona).
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William B. Latter, SIRTF Science Center/California Institute ofTechnology (phone: 626-395-8568, fax: 626-568-0673)
Higher resolution digital versions (300 dpi JPEG and TIFF) of therelease photo are available at:http://oposite.stsci.edu/pubinfo/pr/1999/39/pr-photos.html andhttp://oposite.stsci.edu/pubinfo/pr/1999/39/extra-photos.html
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