- An Atlas of Stellar Spectra
The Atlas of Stellar Spectra and the accompanying outline have been prepared from the viewpoint of the practical stellar astronomer.
http://nedwww.ipac.caltech.edu/level5/ASS_Atlas/MK_contents.html
(Added: Tue Oct 29 2002)
- Annie Jump Cannon
During her career Annie Jump Cannon discovered over 300 variable stars. Her specialty was classifying the characteristics of stars - over 350,000 of them. The results of her work appeared in The Henry Draper Catalogue (1918-24) and The Henry Draper Extension (1925-36).
http://www.wellesley.edu/Anniversary/cannon.html
(Added: Sat Oct 26 2002)
- Doppler Effect and A Star's Motion
The velocity of stars are determined by using the Doppler effect. The motion of a star causes a shift in the wavelengths received.
http://www.astronomynotes.com/starprop/s8.htm
(Added: Sat Oct 26 2002)
- Hydrostatic Equilibrium
The Sun and most stars do not change over long timescales. This implies that they exist in a state of near equilibrium with gravity balanced by pressure.
http://www.astro.soton.ac.uk/~trm/PH112/notes/notes/node103.html
(Added: Sat Oct 26 2002)
- Luminosity and Spectral Class
The classification of stars according to their spectra; each major spectral classification is given a letter, with additional numbers providing further subdivisions.
http://www.glyphweb.com/esky/default.htm?http://www.glyphweb.com/esky/concepts/spectralclassification.html
(Added: Sat Oct 26 2002)
- Magnitudes and Distance
This primer describes the magnitude system and derives all of the equations relating magnitudes to distances.
http://www.astro.nwu.edu/labs/m100/mags.html
(Added: Sat Oct 26 2002)
- Mass-Luminosity Relationship
Detailed observations, particularly in binary star systems where masses can be determined with some reliability, indicate that there is a correlation between the mass of a star and its luminosity.
http://csep10.phys.utk.edu/astr162/lect/binaries/masslum.html
(Added: Sat Oct 26 2002)
- Spectroscopic Parallax
Given a star's apparent magnitude and its luminosity (absolute magnitude), the distance can be determined.
http://www-astro.physics.ox.ac.uk/~sr/lectures/lecture13/img10.htm
(Added: Sat Oct 26 2002)
- Standard Candle
Standard candles are one of the critical ways we have found to help us measure cosmic distances. The principle, if not the application, is quite simple: if you could find an object whose luminosity (brightness) you knew absolutely just from looking at it, then by comparing the apparent luminosity with the absolute luminosity, you could figure how far away it was.
http://www.powersof10.com/powers/tools/station_232.html
(Added: Sat Oct 26 2002)
- Stars - Hubble Space Telescope
This site contains Hubble Space Telescope images of stars.
http://oposite.stsci.edu/pubinfo/stars.html
(Added: Tue Oct 29 2002)
- Stefan-Boltzmann Law
The Stefan-Boltzmann Law states that total spectral radiant exitance (W) leaving a blackbody is proportional to the fourth power of its temperature (T).
http://orbit-net.nesdis.noaa.gov/arad/fpdt/tutorial/sblaw.html
(Added: Sat Oct 26 2002)
- Stellar Magnitudes
A basic observable quantity for a star is its brightness. Because stars can have a very broad range of brightness, astronomers commonly introduce a logarithmic scale called a magnitude scale to classify the brightness.
http://csep10.phys.utk.edu/astr162/lect/stars/magnitudes.html
(Added: Tue Oct 29 2002)
- Stellar Magntitude System
Star magnitudes do count backward, the result of an ancient fluke that seemed like a good idea at the time. The story begins around 129 B.C., when the Greek astronomer Hipparchus produced the first well-known star catalog.
http://skyandtelescope.com/howto/basics/article_238_1.asp
(Added: Sat Oct 26 2002)
- Stellar Masses
An important application of binary systems is that under favorable circumstances they provide one of the only ways to determine reliable masses for stars.
http://csep10.phys.utk.edu/astr162/lect/binaries/mass.html
(Added: Sat Oct 26 2002)
- Stellar Parallax - Applet
Stellar distance estimates are crucial to understanding stellar properties and underpin the whole distance network for galactic and extragalactic astronomy.
http://instruct1.cit.cornell.edu/courses/astro101/java/parallax/parallax.html
(Added: Sat Oct 26 2002)
- Stellar Spectra
An absorption spectrum is produced when a continuum passes through "cooler" gas. Photons of the appropriate energies are absorbed by the atoms in the gas. Although the photons may be re-emitted, they are effectively removed from the beam of light, resulting in a dark or absorption feature. The atmospheres of stars act as a cooler blanket around the hotter interior of a star so that typical stellar spectra are absorption spectra.
http://casswww.ucsd.edu/public/tutorial/Stars.html
(Added: Sat Oct 26 2002)
- The Harvard Spectral Sequence
By late in the last century it was realized that the spectra of stars (in particular, their patterns of absorption lines) had systematic features that could be classified into what came to be known as the Harvard Spectral Sequence.
http://csep10.phys.utk.edu/astr162/lect/stars/harvard.html
(Added: Sat Oct 26 2002)
- The Spectral Sequence as a Temperature Sequence
At first the Harvard Spectral Sequence was thought to reflect different compositions for different stars. We now know that the different spectral types are primarily a consequence of different surface temperatures for the stars, with composition differences playing only a minor role.
http://csep10.phys.utk.edu/astr162/lect/stars/spectra.html
(Added: Tue Oct 29 2002)
- Why do star twinkle?
Stars twinkle because of turbulence in the atmosphere of the Earth. As the atmosphere churns, the light from the star is refracted in different directions. This causes the star's image to change slightly in brightness and position, hence "twinkle."
http://curious.astro.cornell.edu/question.php?number=114
(Added: Sat Oct 26 2002)
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