How Our Milky Way Galaxy Got Its Spiral Arms

Space.com ^ | Feb. 12, 2014 | Katia Moskvitch

[rickmichaels]

The shape of the Milky Way galaxy, our solar system's home, may look a bit like a snail, but spiral galaxies haven't always had this structure, scientists say.

In a recent report, a team of researchers said they now know when and how the majestic swirls of spiral galaxies emerged in the unicerse. Galaxies are categorized into three main types, based on their shapes: spiral, elliptical and irregular. Almost 70 percent of those closest to the Milky Way are spirals. But in the early universe, spiral galaxies didn't exist.

A husband and wife team of astronomers, Debra Meloy Elmegreen at Vassar College in Poughkeepsie, N.Y., and Bruce Elmegreen at IBM's T.J. Watson Research Center in Yorktown Heights, N.Y., analyzed an image from the Hubble Space Telescope known as the Ultra Deep Field. It was taken over a four-month period in late 2003 and early 2004. The picture shows about 10,000 galaxies of different ages, some nearly as old as the universe itself. [Galaxies of the Universe Explained by Type (Infographic)]

To analyze this image, the researchers first sorted the galaxies into several basic types, "such as disk-like, clumpy, elliptical, tadpole-shape and double," said Debra Elmegreen. "We did this for all of the galaxies larger than 10 pixels in diameter, which we thought were large enough to classify, [which came to] about 1000 galaxies."

The scientists then used these classifications to study the most peculiar type of galaxy, a "very clumpy" type that does not really occur anymore in the current universe. However, the researchers established that most young galaxies were born very clumpy, because of gravitational instabilities in a highly turbulent, gas-rich disk.

[KoRn]

/mark

[no-to-illegals]

Love the spiral galaxies. Am reminded somewhat of a starfish going into full hug mode.

[TigersEye]

The Milky Way has a right to bear arms ... even if they are spiral.

[boop]

I'm sorry for being stupid, but if we're at the edge of one "arm" of our galaxy how do we know that it's a spiral?

We see other odd shaped galaxies. Why not us?

[CurlyDave]

And here I always thought it was “conservation of angular momentum” a concept from freshman physics that explains why the planets are all in the same plane around the sun, and why spiral galaxies are pretty much all in one plane also.

It also tells us that most stars should have planets, which was a radical concept up until 20 years ago.

[SunkenCiv]

Thanks KoRn.

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