Physical Cosmology

Why do we call our galaxy the Milky Way?
Answered by Science Channel
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    Science Channel

  1. From Earth, we see much of the Milky Way as a band of light in the nighttime sky. It's the brightest constant object in our sky. Ancient Greeks called this pale spill of stars the galaxies kuklos or "milky circle." At some point, the Romans changed the galaxy's name slightly to the "milky circle" [source: Goddard Space Flight Center]. In 1610, Galileo aimed the first telescope at the heavens, and astronomers have been busy expanding our knowledge of the galaxy ever since.

    Pioneering astronomers didn't have the long-range telescopes we have today. They could detect only visible light, and the dust floating around the Milky Way obscured their views. In 1610, Galileo nevertheless determined that the light of the Milky Way was produced by billions of stars. In the late 1700s, Sir William Herschel, the German-born British discoverer of Venus, claimed the Milky Way was shaped like a disk, with the sun close to its center. In 1920, Dutch astronomer Jacobus Kapetyn developed the parallax method of measuring distances to stars and provided measurements to support Herschel's claim.

    We now know that the Milky Way has stars that are young and intermediate in age, along with gas and stars that are just forming. Dust in the disk shape first mentioned by Herschel makes stars appear more reddish. Newly forming stars are out in the galaxy's spiral arms and with special imaging, a bar of older (white-appearing) stars shows in the center. One of the challenges of studying the Milky Way is that we can't perch comfortably at a perfect distance across the universe to observe and measure it. As earthlings, we sit right in the middle of the galaxy. That would be like measuring and planning the design for a new living room while stuck to the middle of the floor. And by the way, the floor, you and all of the objects in the room are spinning. Instead, scientists make actual observations of wavelengths and compare them with models of how particles and magnetic fields interact in the Milky Way [source: NASA].

    With all that's going on in our galaxy, "Milky Way" seems like a relatively calm name. Then again, if you head away from city lights on a summer evening and fully enjoy the spectacle that it is, the name first assigned to our galaxy in ancient times fits quite nicely.

     

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