Glenn Elert
bent | chaos | eworld | facts | physics
The Physics Factbook™
Edited by Glenn Elert -- Written by his students
An educational, Fair Use website
topic index | author index | special index
| Bibliographic Entry | Result (w/surrounding text) |
Standardized Result |
|---|---|---|
| Coble, Charles R., Elaine G. Murray & Dale R. Rice. Earth Science. New Jersey: Prentice-Hall, 1987: 46. | "The Milky Way Galaxy to be about 100,000 light-years in diameter" | 100,000 light year |
| "Milky Way." Microsoft Encarta 96 Encyclopedia CD-Rom. Funk & Wagnalls, 1996. | "The diameter of the disk is about 100,000 light-years" | 100,000 light year |
| Goodwin, Simon. Hubble's Universe: A Portrait of Our Cosmos.New York: Penguin, 1996: 9. | "Disk-shaped island about 100,000 light years across" | 100,000 light year |
| Arny, Thomas and Nicholas A. Pananides. Introductory Astronomy. 2nd ed. Massachusetts: Addison-Wesley, 1979: 291. | "The Milky Way is about 100,000 light years across" | 100,000 light year |
| Cohen, Nathan, and Donald Goldsmith. Misteries of the Milky Way. Chicago: Contemporary Books, 1991: 291. | "… a hundred thousand light-years from rim to rim" | 100,000 light year |
The Milky Way Galaxy, a spiral galaxy, homes our solar system
together with lest 200 billion other stars. The Milky Way is also
referred to the portion of the Milky Way Galaxy that can be seen
by the naked eye from the earth. It appears to look like a milk
band of light stretching across the sky.
The structure if the galaxy is like a disk with a bulge in the
center with clouds of dust and gases which surrounds it and prevents
us from seeing into the center. The diameter has been measured
to be about 100,000 light-years. One light year is the distance
at which light travels in a year (9.46 trillion kilometers).
The diameter of the galaxy was determined by the use of variable
stars (also known as Cepheid variables), or stars whose luminosity
changes with time. Harlow Shapley was the astronomer that discovered
the relationship between its brightness and distance. It was found
that the change in its brightness was predictable because its
change from maximum brightness to dimness occurred in a cycle.
The advantage to this finding allowed Shapley to find its absolute
brightness by measuring the period. Shapley thus obtained the
distance when he compared the brightness to a Cepheid variable
distance scale because the distance to other stars were known.
This pave the way for other astronomers to determine not only
the distance of our galaxy but others too.
Karian Fung -- 1998
| Another quality webpage by Glenn Elert |
|
home | contact bent | chaos | eworld | facts | physics |
