In our Galaxy, there are some old stars and some young ones. While the Sun is old compared to you, it is young compared to the Galaxy.
Look at where the Sun is in our Galaxy. There are many more stars in
the center part than in the spiral arms where the Sun is. Can you
imagine what the sky might look like if our Sun, and the Earth, lived
near the center of the Galaxy, our star-city?
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Questions and answers about the Milky Way
A Matter of Scale - interactive showing the sizes of things, from very tiny to huge - from NSF
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The Milky Way galaxy is the
spiral galaxy we call home, as do roughly 100 billion other
stars. It looks very much like other spiral galaxies when viewed from
above. There are spiral arms and a bright central part. The Sun is
far from the center of the Galaxy, halfway to the edge of the Galaxy
along the Orion spiral arm.
The Sun is revolving around the center of the Galaxy at a speed of half a million miles per hour, yet it will still take 200 million years for it to go around once. Do you feel like you are moving at that speed through space? If you did, you would certainly need a seat belt! When we run, we feel the wind on our bodies because there are molecules which make up the air that push against our bodies. But there are very few molecules in the space between the stars. So there is nothing to push against our planet so that we "feel" like we are rushing around at half a million miles per hour.
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A galaxy like the Milky Way as viewed from the top, and the
actual Milky Way as viewed in the infrared
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Like other spiral galaxies, the Milky Way has a bulge, a disk, and a halo. Although all are parts of the same galaxy, each contains different objects. The halo and central bulge contain old stars and the disk is filled with gas, dust, and young stars. Our Sun is itself a fairly young star at only 5 billion years old. The Milky Way galaxy is at least 5 billion years older than that. |
Questions and answers about the Milky Way
A Matter of Scale - interactive showing the sizes of things, from very tiny to huge - from NSF
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The Milky Way is the spiral
galaxy we call home, as do roughly 100 billion other stars. It
looks very much like other spiral galaxies when viewed from above.
There are spiral arms and a nucleus. The Sun can be found rather far
from the center of the Galaxy, halfway to the edge of visible matter
along the Orion spiral arm. The Sun is revolving at a speed of
half a million miles per hour around the center of the Galaxy, yet it
will still take 200 million years for it to go around once.
Radio observations of gas in our Galaxy reveal that the gas is feeling the gravitational effect of matter far beyond the edge of the visible Galaxy. Astronomers call this material dark matter, since electromagnetic radiation from it is not currently detectable at any wavelength.
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A galaxy like the Milky Way as viewed from the top, and the
actual Milky Way as viewed in the infrared
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Like other spiral galaxies, the Milky Way has a bulge, a disk, and a
halo. Although all are parts of the same galaxy, each contains
different types of objects. The central bulge contains old stars, the
halo houses globular
clusters and dark matter, and the disk is filled with gas, dust,
and young stars. Our Sun is itself a fairly young star at only 5
billion years old. The Milky Way is at least 5 billion years older
than that. The ages of globular clusters suggest that it may be
closer to 10 billion years older.
Recent observations of the numbers and distributions of stars in the Galaxy suggest that it may have a bar! |
Questions and answers about the Milky Way
A Matter of Scale - interactive showing the sizes of things, from very tiny to huge - from NSF
Last modified January 11, 2006 by Travis Metcalfe.
The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. All Rights Reserved. Site policies and disclaimer