Download Three of his best known contributions

[실습] Hubble’s Law
2009. 05. 27.
Hubble’s Law
<Three of his best known contributions>
<First, expansion of stellar distance scale>
Edwin Hubble
1953)
* Period – Luminosity Relation of Cepheid Variable
(1889 ~
(Henrietta Leavitt, 1912)
* ‘Shapley-Curtis debate’ in 1920
* Cepheid Variable of M31 using Mount Wilson 100-inch telescope
=> Andromeda Galaxy(not Nebula), ‘Island Universe!’
<Second, cataloguing of distinct types of galaxies>
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Elliptical Galaxies – E0 ~ E7
Spiral Galaxies – Sa ~ Sc /
Lenticular Galaxies – S0
Irregular Galaxies...
SBa ~ SBc
<Third, Velocity-Distance Relation among Extra-Galaxy>
Hubble’s Law
<Third, Velocity-Distance Relation among Extra-Galaxies>
* A Relation Between Distance and Radial Velocity
Among Extra-Galactic Nebulae (1929, Edwin Hubble)
* V = H * d ( V : radial velocity, d : distance of galaxy)
(H : Hubble Constant)
745km/s for a distnace of 1.4Mpc
=> ~500km/s/Mpc
Expanding Universe
Edwin Hubble
(1889 ~ 1953)
Hubble’s Law
<Third, Velocity-Distance Relation among Extra-Galaxies>
* Universe Age using Hubble Constant (H)
Edwin Hubble
(1889 ~ 1953)
=> About 2/3 of the calculated result, in this case 13 billion years...
* Universe Size using Hubble Constant (H)
 Assuming H=50, this givea size of 19.5 billion light years.
 Gravity reduction factor of about 2/3 is sometimes applied
as it is for age, 13 billion light years...
Hubble’s Law
<Finding the recessional velocity of a galaxy>
=>Using “Doppler Effect”
Hubble’s Law
<Finding a galaxy’s actual size and angular size>
=>Assume that “All galaxies of the same type are the same physical size”
Hubble’s Law
<Hubble’s Law Data Spreadsheet>
Hubble’s Law
<Hubble’s Law Experimental Web Site>
http://www.astro.washington.edu/courses/labs/clearinghouse/labs/HubbleLaw/hubbles_law_preselected.html
Galaxy List : http://www.astro.washington.edu/courses/labs/clearinghouse/labs/HubbleLaw/galaxies.html
Ppt : http://www.astro.washington.edu/courses/labs/clearinghouse/labs/HubbleLaw/hubbleslaw_spreadsheet.xls
<Follow Question>
1.What are your values for the Hubble constant, maximum age of the Universe, and the age
considering deceleration due to gravity?
2. Identify the galaxy with the highest redshift and state its recessional velocity.
What fraction of the speed of light is that galaxy receding from us?
3. Why does the best-fit line to your data need to go through the origin of your graph?
4. Quantitatively compare your maximum age for the Universe to the age of the Sun (5 billion
years), and to the age of the oldest stars in the Milky Way (approximately 12.5 billion years).
5. What is the currently accepted value for the Hubble constant? How does your value compare?