<IMG SRC="/images/sci/nor/ngc891.jpg"> <H2>ISO detects signal from dark matter in a galaxy similar to the Milky Way</H2> A true colour photograph of the edge-on Spiral galaxy NGC 891 (field of view is 6.7 x 6.7 arcminutes). The dark band running through the center of the disk is caused by the effect of large dust clouds in this galaxy. At 8 positions in this disk, even beyond the field of this photo, the ISO-SWS has detected the signal from molecular hydrogen gas (H2). <P> The graphical inset shows the signal of the H2 lines at 17.0 and 28.2 micrometer wavelength, detected at the outermost position of the survey, at a distance 12 kilo parsec (37000 light-years) from the center, a position where other observations of lines of molecules, like the CO molecule, are trailing into the noise. From the ratio of the signal strength of these lines a temperature of the gas of about 80K is derived. <P> Credits:<BR> ISO-SWS data from Valentijn and van der Werf / SRON <BR> Optical photograph of NGC 891: Blair Savage, Chris Howk (U. Wisconsin)/N.A.Sharp (NOAO)/AURA/NSF <BR> <P> These observations were discussed in details in a ESA Science Web Note: <P> "<A HREF="http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=12820">[<EM>ISO detects signal from dark matter in a galaxy similar to the Milky Way</EM>]</A>"<BR> <P> <B>High-resolution images of the Galaxy NGC891 are available at NOAO:</B> <A HREF="http://www.noao.edu/image_gallery/html/im0002.html">http://www.noao.edu/image_gallery/html/im0002.html</A> <BR> <P>