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#Mon Aug 09 11:42:17 CEST 2010
Text__ZLPLwKOaEd-WfYQ0GneCwQ_title=How Massive is a Galaxy ?
Text__ZLPLwKOaEd-WfYQ0GneCwQ_text=Measuring the mass of stellar and galactic objects usually is a tough problem in astrophysics. <p>Thus it is highly welcome that gravitational lenses allow to directly determine the mass of a galaxy.</p><p>For instance one can use the fact, that for an Einstein ring the mass of the lense is directly proportional to the square of the diameter of the ring.</p>