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?


The Solar Spectrum

http://ess.geology.ufl.edu/ess/Notes/040-Sun/spectrum.GIF




Stellar Spectra

http://homepages.wmich.edu/~korista/phys325.html




Stellar Spectra

http://www.maryspectra.org/classical/classical.htm

[Our Sun is type G2]






Stellar Spectra -- Composition

http://faculty.fortlewis.edu/tyler_c/classes/206/notes4.htm




Stellar Spectra--Color and Brightness

http://www.oswego.edu/~kanbur/a100/images/planck.jpg

Wien’s Law Stefan-Bolzmann Law




HR Diagram:Luminosity vs Temperature

http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html




HR Diagram and Mass

http://physics.uoregon.edu/~jimbrau/astr122/Notes/Chapter17.html

Lowest Mass:about 0.072 Msun

Highest Mass:about 150 Msun




Low mass more common than High mass

http://zebu.uoregon.edu/textbook/imf1.gif




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?




Star Sizes

http://commons.wikimedia.org/wiki/Category:Star_size_comparisons




HR Diagram and Radius

http://abyss.uoregon.edu/~js/ast122/lectures/lec11.html




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




http://astro.unl.edu/classaction/loader.html?filename=animations/stellarprops/hrexplorer.swf&movieid=hrexplorer&width=805&height=665&version=6.0.0








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.




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?


• 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.


http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19






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?


Proper Motion (Imaging)

http://csep10.phys.utk.edu/astr162/lect/motion/proper.html




Radial Velocity using Doppler Shift (Spectroscopy)

http://spiff.rit.edu/classes/phys301/lectures/doppler/doppler.html




Spectroscopic Binaries(Spectroscopy)

http://csep10.phys.utk.edu/astr162/lect/binaries/spectroscopic.html21Thursday, April 22, 2010

http://csep10.phys.utk.edu/astr162/lect/binaries/spectroscopic.html

http://csep10.phys.utk.edu/astr162/lect/binaries/spectroscopic.html

Eclipsing Binaries(Photometry)

http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap17/FG17_21.jpg




Light curve of 2MASS J05352184–0546085 at 0.8 m

http://www.nature.com/nature/journal/v440/n7082/fig_tab/nature04570_F1.html






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,






http://www.absoluteastronomy.com/topics/Angular_diameter

http://www.absoluteastronomy.com/topics/Angular_diameter

http://www.absoluteastronomy.com/topics/R_Doradus

http://www.absoluteastronomy.com/topics/R_Doradus

http://www.absoluteastronomy.com/topics/Light_Years

http://www.absoluteastronomy.com/topics/Light_Years

http://www.absoluteastronomy.com/topics/Beach_ball




http://www.absoluteastronomy.com/topics/Stadium

http://www.absoluteastronomy.com/topics/Stadium

Stellar Diameters(Photometry)


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.




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




Radius-Mass Ratios

http://www.astrophysicsspectator.com/topics/overview/SizeStarsPlanets.html




Radius-Mass Ratios


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.




Brown Dwarfs: Sizes

http://homepages.wmich.edu/%7Ekorista/stargal-images/sunMLTJ_visseq.jpg




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?


• 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.








a1 16 stars

Education

stellar mass

low mass

aboutan hr diagram

masshighest mass

msunlowest mass

massive stars

stellar spectrahttp

stellar spectraour