ll9



    HENRY       gravitationally holding it together°    We though it might be
    (CONT 'D)
                in the form of ionized hydrogen.    We looked for Lyman-alpha

                radiation, red shifted from the ionized hydrogen, and we

                didn't see any.    We set a lower limit, which certainly ex-

                cludes the possibility that the Coma cluster is held together
J
                by this ionized hydrogen.    I think that may leave a real

                mystery as to what is holding the thing together.


                The fourth point may turn out to be the most interesting

                thing of all.   When you look in the Milky Way, you see a

                lot of UV coming from the stars, but the question is, what

                do you see when you look up to the North Galactic Pole or

                down to the South Galactic Pole.    One of the most exciting

                results of X-ray astronomy was the fact that an X-ray back-

                ground was observed over the sky that nobody had expected,

                and part of this is the gamma-ray background that Dr. Trombka

                talked about.   In the UV, nobody knows, but you never know

                until you look.    You do have to deal with this background

                of stars that we know is there.    So we did look at a large

                number of different points at high galactic latitudes, both

.               north and south.    The spectrum that we see is above this

                dark count.   In other words, this abnormally high dark

                current did not, in fact, interfere with that experiment.

                The spectrum that we see looks like the spectrum of the hot