Download - A1 16 Stars
Hertzsprung–Russell diagramLACC §16.2 16.3, 17.4
• Spectral Classes
• Luminosity Classes
• distribution; masses & lifetimes
An attempt to answer the “big questions”: What is out there?
1Thursday, April 22, 2010
30 Second People Study
• Imagine you are from an alien race who live out their lives at an accelerated rate.
• Imagine you have discovered the planet Earth with your advanced telescopes which allow you to make observations of Earth’s human population.
• After collecting data for about 30 seconds, what would you be able to say about human physiology?
2Thursday, April 22, 2010
The Solar Spectrum
http://ess.geology.ufl.edu/ess/Notes/040-Sun/spectrum.GIF
3Thursday, April 22, 2010
Stellar Spectra
http://homepages.wmich.edu/~korista/phys325.html
4Thursday, April 22, 2010
Stellar Spectra
http://www.maryspectra.org/classical/classical.htm
[Our Sun is type G2]
5Thursday, April 22, 2010
Stellar Spectra -- Composition
http://faculty.fortlewis.edu/tyler_c/classes/206/notes4.htm
6Thursday, April 22, 2010
Stellar Spectra--Color and Brightness
http://www.oswego.edu/~kanbur/a100/images/planck.jpg
Wien’s Law Stefan-Bolzmann Law
7Thursday, April 22, 2010
HR Diagram:Luminosity vs Temperature
http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html
8Thursday, April 22, 2010
HR Diagram and Mass
http://physics.uoregon.edu/~jimbrau/astr122/Notes/Chapter17.html
Lowest Mass:about 0.072 Msun
Highest Mass:about 150 Msun
9Thursday, April 22, 2010
Low mass more common than High mass
http://zebu.uoregon.edu/textbook/imf1.gif
10Thursday, April 22, 2010
The stars we see -- m vs M
http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html
Why aren’t they
mostly M and K
type stars?
11Thursday, April 22, 2010
Star Sizes
http://commons.wikimedia.org/wiki/Category:Star_size_comparisons
12Thursday, April 22, 2010
HR Diagram and Radius
http://abyss.uoregon.edu/~js/ast122/lectures/lec11.html
13Thursday, April 22, 2010
Stellar Mass and Lifetimes
http://www.frostydrew.org/observatory/courses/astro/mass_life.gif
0.07 Msun
last about 10,000,000,000,000
years
150 Msun last about
1,000 years
NOTE: This in not an HR Diagram.On an HR Diagram, massive stars would be on the top left, not the bottom right
14Thursday, April 22, 2010
Main Sequence Turn-Off Point
http://astro.berkeley.edu/~dperley/univage/univage.html
H-R diagrams of two clusters, the open cluster M67 (a young cluster), and the globular cluster M4 (an old cluster). The main sequence is significantly shorter for the older
cluster; the luminosity and temperature of stars at the 'turnoff point' can be used to date these clusters.
15Thursday, April 22, 2010
Hertzsprung–Russell diagramLACC §16.2 16.3, 17.4
• Spectral Classes: O B A F G K M; blue (hot) --> red (cool); Wien’s Law (λ ∝ 1/T); absorption features
• Luminosity Classes: I II III IV V; supergiant (I) --> dwarf (V); Stefan-Bolzmann Law (Flux ∝ T4); size (increases as you move up and right)
• distribution: (main sequence (90%), white dwarfs (10%), blue giants (rare), red dwarfs (common), red giants (dying), white dwarfs (dead)); masses & lifetimes: blue m.s. (high mass, short life) --> red m.s. (low mass, long life)
What is out there?
16Thursday, April 22, 2010
• Ch 17, p. 392-393: 13 (expect test question(s) like this)
• Ch 18: Image Analysis Quizzes accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19
Due beginning of next class period.
LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,
3rd ed.
17Thursday, April 22, 2010
StarsLACC §16.2 16.3, 17.4
• Spectroscopy
• Imaging
• Photometry
An attempt to answer the “big questions”: What is out there? How big is the universe?
18Thursday, April 22, 2010
Proper Motion (Imaging)
http://csep10.phys.utk.edu/astr162/lect/motion/proper.html
19Thursday, April 22, 2010
Radial Velocity using Doppler Shift (Spectroscopy)
http://spiff.rit.edu/classes/phys301/lectures/doppler/doppler.html
20Thursday, April 22, 2010
Spectroscopic Binaries(Spectroscopy)
http://csep10.phys.utk.edu/astr162/lect/binaries/spectroscopic.html21Thursday, April 22, 2010
Eclipsing Binaries(Photometry)
http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap17/FG17_21.jpg
22Thursday, April 22, 2010
Light curve of 2MASS J05352184–0546085 at 0.8 m
http://www.nature.com/nature/journal/v440/n7082/fig_tab/nature04570_F1.html
23Thursday, April 22, 2010
Stellar Diameters: Betelgeuse (Imaging)
http://www.lesia.obspm.fr/~titania/results.html
Because of the size and proximity of this star it has the third largest angular diameter as viewed from Earth, smaller only than the Sun and R Doradus.
[Betelgeuse] is one of only a dozen or so stars telescopes have imaged as a visible disk....The distance to Betelgeuse is not known with precision but if this is assumed to be 640 light years, the star's diameter would be about 950 to 1000 times that of the Sun. Betelgeuse ... is thought to have a mass of about 20 solar masses.
Though only 20 times more massive than the Sun, this star could be hundreds of millions times greater in volume (as with a beach ball compared to a large stadium). Betelgeuse was the first star on which starspots were resolved in optical images by a telescope,
24Thursday, April 22, 2010
Stellar Diameters(Photometry)
http://www.lesia.obspm.fr/~titania/results.html
The star being at 170 parsecs from the Earth, this yields a stellar radius of 10 solar radii, a reasonable value for this kind of stars.
The occulted star, a K0 giant, has an angular diameter of 0.55 mas (not 1.11 mas, as indicated erroneously on the figure, to be corrected), corresponding to 7.5 km projected at Titania.
25Thursday, April 22, 2010
Brown Dwarfs
http://www.spaceflightnow.com/news/n0205/22closest/
Astronomers have found many types of objects in orbit around stars. These range from other full-sized stars like our sun (binary star systems) to Jupiter sized planets (never directly imaged but inferred from radial-velocity spectroscopy). The relative sizes of these various types of bodies are shown above for comparison. Even though a brown dwarf can be similar in diameter to a Jupiter sized planet, brown dwarfs are 13-75 times more massive and they can appear on the order of 100-1,000,000 times brighter than a Jupiter sized planet at infrared wavelengths when they are studied with telescopes. Credit: Gemini Observatory/Artwork by Jon Lomberg
26Thursday, April 22, 2010
Radius-Mass Ratios
http://www.astrophysicsspectator.com/topics/overview/SizeStarsPlanets.html
27Thursday, April 22, 2010
Radius-Mass Ratios
http://www.astrophysicsspectator.com/topics/overview/SizeStarsPlanets.html
The material inside a degenerate object like Saturn is softer than in the smaller planets; unlike the solid rock of Earth, the material at the center of Saturn gives when it is squeezed. This means that as the mass of a degenerate object increases, which increases the pressure required to counter the object's self-gravity, the density also increases. The consequence is that the radius can decrease as the mass increases. For cold bodies of the same composition, the radius goes as the inverse of the cube root of the mass. For bodies with some internal heat—and generally there is some internal heat left over from the creation of the body—the radius decreases more slowly than for the cold bodies as the mass rises. This residual heat causes Jupiter to be slightly larger than Saturn, and it causes most of the known brown dwarfs to be about the size of, rather than much smaller than, Jupiter.
28Thursday, April 22, 2010
Brown Dwarfs: Sizes
http://homepages.wmich.edu/%7Ekorista/stargal-images/sunMLTJ_visseq.jpg
29Thursday, April 22, 2010
StarsLACC §16.2 16.3, 17.4
• Spectroscopy: Temperature, Composition, Radial Velocity, Age of a Cluster, Binary Systems (Spectroscopic Binaries)
• Imaging: Diameters, Proper Motion, Binary Systems (Visual Binaries) Clusters (Open vs Globular)
• Photometry: Variable Stars, Diameters, Binary Systems (Eclipsing Binaries); light curves
An attempt to answer the “big questions”: What is out there? How big is the universe?
30Thursday, April 22, 2010
• Ch 16, pp. 371-372: 6.
• Ch 19: Image Analysis Quizzes accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19
Due beginning of next class period.
LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,
3rd ed.
31Thursday, April 22, 2010