A new analysis that refutes challenges to the existence of dark matter in certain galaxies appears in an article published this week in the journal Nature. Leading author of the article is Avishai Dekel, professor of physics at the Hebrew University of Jerusalem.
Illustration of computer simulation showing two spiral galaxies combining to form an elliptical galaxy at right.
Accepted cosmological theory postulates that every observable galaxy in the universe (each made up of billions of stars similar to our sun) is embedded in a massive “halo" of dark matter. Though unseen, dark matter can be clearly detected indirectly by observing its tremendous gravitational effects on visible objects.
This common understanding faced a severe challenge when a team of astronomers, writing in Science in 2003, reported a surprising absence of dark matter in one type of galaxy – “elliptical" (rounded) galaxies. Their theory was based on observations that stars located at great distances from the center in such galaxies move at very slow speeds, as opposed to the great speed one would have expected from the heavy gravitational pull exerted by dark matter.
Jerry Barach | alfa
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