TEMPERATURE
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Transcript of TEMPERATURE
TEMPERATURE
A star’s color depends on its surface temperature
How hot is Vega?
l (Å)
lmax at 4600 Å
BB spectrum
So, Wien’s law tells us
K630010x4600
10x8977.210
3
VegaT
Vega is 500 Khotter than the Sun
SPECTRUM
Never Say Never• Auguste Comte (1798 - 1857)– French Philosopher (bad prophet)– Founder of the Social Sciences– Espoused the philosophy of positivism – as seen on the
Brazilian flag – “Love as a principle and order as the basis; progress as the goal.”
“there is no conceivable means by which we shall one day determine the chemical composition of the stars”
Continuous spectrum
l
l
Blackbody spectrum
Classify Stars into groups based on Spectral Data
The Spectral Sequence• In 1890, Edward Pickering and
his assistant at Harvard classified thousands of stellar spectra at Harvard.
• Named them ‘A’ through ‘Q’
• A. Cannon ‘improved’ the scheme and ordered it by temperature: O,B,A,F,G,K,M
• Subdivided each into 0 through 9 (AO: hot – A9:cooler)
E. Pickering and his housekeeper W. Fleming
A. J. Cannon classifying one of 200,000 spectra by eye for 25¢ an hour ($6 today)
Annie Jump Cannon (1863 - 1941)studied over 250,000spectra as part of theHarvard Observatory
program to classify stars
Spectral Type Classification System
O B A F G K MOh Be A Fine Girl/Guy, Kiss Me (Long Time)!
50,000 K 1,000 K Temperature
Only Brilliant Astronomers Find Glorious Knowledge Manning Large Telescopes
Only Boring Astronomers Find Gratification Knowing Mnemonics Like That…
MAGNITUDE
Star Apparent Magnitude
Distance (pc)
Absolute Magnitude
Luminosity (Sun=1)
Sun -26.74 - 4.83 1
Sirius -1.44 2.6371 1.45 22.5Arcturus -0.05 11.25 -0.31 114Vega 0.03 7.7561 0.58 50.1Spica 0.98 80.39 -3.55 2250Barnard's Star 9.54 1.8215 13.24 1/2310
Proxima Centauri 11.01 1.2948 15.45 1/17700
Flowchart of Key Stellar Parameters