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The Sombrero II

July 3, 2012

Messier 104 is one of the most photogenic galaxies in the nearby universe. A lane of dark dust outlines its edge like the brim of a hat, giving M104 a distinctive nickname: the Sombrero.

Because of that broad rim, astronomers have long classified the Sombrero as a spiral galaxy, similar to our own Milky Way. But a recent study says that’s not quite right — the galaxy is really a sort of hybrid — a cross between a spiral and another type of galaxy known as an elliptical.

The study was headed by Dimitri Gadotti of the European Southern Observatory. It showed that the bulk of the Sombrero closely resembles an elliptical — a shape like a fat, fuzzy football. Such galaxies consist mainly of old, faint stars. They give birth to almost no new stars because they don’t have much gas and dust — the raw materials for making stars. And the Sombrero is surrounded by about 2,000 clusters of especially old stars — a number usually associated with ellipticals, not spirals.

Yet the wide brim that gives the Sombrero its name has the look of a spiral — a broad, flat disk with lots of gas and dust to spawn new stars.

The study suggests that the galaxy is basically a big elliptical. Several billion years ago, though, it pulled in vast amounts of gas and dust. That material encircled the galaxy’s center, forming a wide, thin disk. That would make the Sombrero two galaxies in one — a vigorous young spiral sitting inside an old, fat elliptical.


Script by Damond Benningfield, Copyright 2012


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