Galaxy Without Dark Matter Puzzles Astronomers

What do you call an absence of darkness? Dark matter is supposed to be spread throughout the universe, but a new study reports a spiral galaxy that seems to be empty of the stuff, and astrophysicists cannot easily explain why. In the outer regions of most galaxies, stars orbit around the center so fast that they should fly away. The combined mass of all the observable inner stars and gas does not exert strong enough gravity to hold onto these speeding outliers, suggesting some mass is missing. Most astronomers believe that the missing mass is made up of what is called dark matter, which forms vast spherical halos around each galaxy. However, in the spiral galaxy NGC 4736, according to scientists at the Polish Academy of Science in Krakow, ordinary luminous stars and gas can account for all the mass in NGC 4736; in other words, no dark matter. But some scientists aren't so sure.

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