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The Empirical Properties of Stars

The first astronomers characterized the stars by their brightness and color.  They described the brightness of the stars through a magnitude system that is attributed to the Greek astronomer Hipparchus.  This ancient system is described in the Almagest of Ptolemy, which was written in the middle of the 2nd century A.D.  In this magnitude system, the brightest stars have magnitude 1, and the dimmest stars have magnitude 6.  Ptolemy lists the magnitudes of the most prominent stars in his Almagest.

Early catalogs in modern times were constructed by Johann Bayer (1603) and John Flamsteed (1725).  These astronomers developed naming systems based on Greek letters (Bayer) and numbers (Flamsteed)  followed by the name of the constellation in the genitive case.  These naming systems are called, respectively, Bayer letters and Flamsteed numbers.  For example, the star Vega has a Bayer letter of α Lyrae (abbreviated as α Lyr) and a Flamsteed number of 3 Lyrae.

By the end of the 19th century, complete catalogs of stellar brightness down to 9th magnitude were constructed; the brightest stars are given a value of 1 in these catalogs.  The first of these catalogs is the Bonner Durchmusterung (BD) (1859-1862) of F.W.A. Argelander, which is complete to 9.5 visual magnitude, and contains many 10th magnitude stars.  This catalog covers stars with declinations between 90° and −2°.  Other catalogs of that era are the Southern Durchmusterung (SD) (1886) of E. Schoenfeld, which covers stars with declinations between −2° and −23° and magnitudes of 9.4 and less, the Cordoba Durchmusterung (CD) (1892-1932) of J.M. Thome, which covers stars with declinations between −42° and −51° and is complete to slightly brighter than 10th magnitude, and the Cape Photographic Durchmusterung (CPD) (1895-1900) of D. Gill and J.C. Kapteyn, which covers stars with declinations ranging from −18° to −90° and is complete to magnitude 9.2.  Stars are often referred to by their number in one of these catalogs; for instance, Vega is listed as BD+38 3238 and is given a visual magnitude of 1.0.  All four of these catalogs can be downloaded from the VizieR data base.

One important catalog from the first-quarter of the 20th century is the Henry Draper Catalog (Cannon and Pickering, 1918–1923), which contains 222,000 stars observed by the Draper Telescope in Cambridge, Massachusetts and the Bache telescope in Arequipa, Peru.  This is a catalog of stellar magnitudes and spectral types.  Often one sees stars listed by their Henry Draper Catalog number.  For instance, Vega has the catalog number HD 172167.  A second widely-used catalog of this era is the General Catalog of 33,342 Stars of Boss (1937), which is complete down to 7th magnitude.

At the beginning of this century, two catalogs were published containing data collected by the Hipparcos satellite: the Hipparcos and the Tycho catalogs.  The first is a catalog of stars with well-determined trigonometric parallaxes and magnitudes, while the second is a larger catalog of stars with well-determined positions.  The largest of the current general catalogs is the All Sky Compiled Catalog (Kharchenko 2001), which contains 2.5 million stars with a limiting magnitude of 12th to 14th magnitude; this catalog is a compilation of a number of other large catalogs, including the Hipparcos and Tycho Catalogs.  A useful, smaller catalog is the Nearby Stars Catalog (Gliese et al. 1991), which is a catalog of all stars with trigonometric parallaxes of 0.0390 or more, which means a distance of 25.64 parsecs or less.  The Bright Star Catalogue (Hoffleit and Warren 1991) is a catalog of stars brighter than 6.5 apparent visual magnitude. It contains 9,096 stars.

Photometry includes more than the measurement of visual magnitude; systems for measuring color magnitude have been developed.  These systems are very important for characterizing stars, because the color of a star is directly related to the star's photospheric temperature.    A color band is defined by a specific filter, and the magnitude of a star at that color is derived by comparing the filtered brightness of the star to the filtered brightness of a reference star.  Vega is the general standard for color magnitude, with it having a magnitude of 0.04 in any color band.  The numerous photometry systems in use are described in the review article Standard Photometric Systems (Bessell 2005) and online in The Asiago Database on Photometric Systems (ADPS) (Munari, Fiorucci, and Moro 2002).  The most-widely used system is the Johnson-Cousins photometry system, which is developed in two papers, “Fundamental Stellar Photometry for Standards of Spectral Type on the Revised System of the Yerkes Spectral Atlas” (Johnson and Morgan 1953) and “VRI Standards in the E Regions.” (Cousins 1976).

The modern spectral type system for stars, which describes stars by the patterns of absorption and emission lines seen in their spectra, was developed at Harvard College Observatory and Yerkes Observatory.  In its final form, this system is known as the MK system, after the authors W.W. Morgan and Philip C. Keenan.  Under it, the star Vega is an A0 V star.  The origin of the system, which was a simple assignment of the letter A through Q to stars based on common line patterns, is presented in the Draper Catalog of Stellar Spectra (Pickering, 1890), which contains 10,351 stars north of declination −25°, most of which are magnitude 6 or brighter.  The system is further developed in the Henry Draper Catalog, which is described above.  This catalog introduced the idea of classifying a star's stellar type through comparison to a standard star.  The link between spectral type and photospheric temperature is developed in this catalog.  The current version of the stellar type system, which is derived from the earlier system of the Henry Draper Catalog, is defined in the Yerkes Catalog, entitled An Atlas of Stellar Spectra (Morgan, Keenan, and Kellman 1943).  The calibration of the system is described in Keenan (1985).  This system has been extended to the brown dwarfs with the addition of two new spectral types, which are described in the article New Spectral Types L and T (Kirkpatrick 2005).

The distance to a star is calculated through parallax measurements.  This is done both from Earth and from satellite.  The Hipparcos Catalog is the most extensive current catalog of stellar parallaxes.

The majority of stars are members of multiple star systems.  Of particular interest are eclipsing binary star systems, because the masses of the individual stars in these systems are easily derived from the Doppler shifts of spectral lines. The orbital parameters for many eclipsing systems is given in the “Catalog of Eclipsing Binaries Parameters” (Perevozkina and Svechnikov 1999).  A broader catalog of stellar masses, derived from resolved binary star systems as well as eclipsing binary systems, is the “Stellar Mass Catalogue” (Belikov 1995).

The radius of a star can be measured through several methods, including occultation by the moon, eclipse by a companion star, and direct measurement through interferometry.  The apparent and absolute sizes of stars are presented in the Catalog of Apparent Diameters and Absolute Radii of Stars (CADARS) (Pasinetti-Fracassini et al. (2001).

The names and basic properties of a star can be found at the Simbad data base.  The properties of individual stars as listed in a variety of catalogs can be found through the VizieR data base.


Star Catalogs

Argelander, Friedrich Wilhelm August.  Bonner Durchmusterung (Bonner Sternverzeichniss 1–3).   (1859-1862).  VizieR catalog I/122.

Boss, B.  General Catalogue of 33342 Stars.  Carnegie Institute of Washington Publication 468 (1937).  VizieR catalog I/113A (1985 version).

Cannon, Annie J., and Pickering, Edward C.  “The Henry Draper Catalogue”  Annals of the Astronomical Observatory of Harvard College 91 (1918): 1–290; 92 (1918): 1–309; 93 (1919): 1–271; 94 (1919): 1–299; 95 (1920): 1–315; 96 (1921): 1–235; 97 (1922): 1–261; 98 (1923): 1–259; 99 (1924): 1–272; 100 (1936): 1–226.

European Space Agency.  The Hipparcos and Tycho CataloguesVizieR catalog I/239.

Gill, D., and Kapteyn, J. C.  “Cape Photographic Durchmusterung.” Annals of the Cape Observatory 3 (1895, “Part I: Zones −18 to −37 Degrees”); 4 (1897, “Part II: Zones −38 to −52 Degrees”); 5 (1900, “Part III: Zones −53 to −89 Degrees”).  VizieR catalog I/108.

Gliese, W., and Jahreiss, H. Preliminary Version of the Third Catalogue of Nearby Stars. Astron. Rechen-Institut, Heidelberg (1991).  VizieR catalog V/70A.

Hoffleit, D., and Warren, W.H., Jr.  The Bright Star Catalogue, 5th Revised Edition.  Astronomical Data Center, NSSDC/ADC (1991).  VizieR catalog V/50.

Kharchenko, N.V. “All-Sky Compiled Catalogue of 2.5 Million Stars.”  Kinematics and Physics of Celestial Bodies 17, (2001): 409.  VizieR catalog I/280A.

Schoenfeld, E.  “Southern Durchmusterungen.”  Astronomische Beobachtungen auf der Sternwarte der Koeniglichen
Rheinischen Friedrich-Wilhelms-Universitat zu Bonn
8, Part IV
(Bonn: Adolph Marcus, 1886).  VizieR catalog I/119.

Thome, J.M.  “Cordoba Durchmusterung.”  Resultados del Observatorio Nacional Argentino 16 (1892, Part I: −22° to −32°); 17 (1894, Part II −32° to −42°); 18 (1900, Part III, −42° to −52°); 21 (Part I) (1914, Part IV, −52° to −42°); 21 (Part II) (1932, Part V: −62° to −90°)  VizieR catalog I/114.


Bessell, Michael S.  “Standard Photometric Systems,” in Annual Review of Astronomy and Astrophysics, vol. 43.  Palo Alto: Annual Reviews, 2005: 293–336.

Cousins, A.W.J.  “VRI Standards in the E Regions.”  Memoirs of the Royal Astronomical Society 81 (1976): 25–36.

Johnson, H.L., and Morgan, W.W.  “Fundamental Stellar Photometry for Standards of Spectral Type on the Revised System of the Yerkes Spectral Atlas.”  The Astrophysical Journal 117 (May 1953): 313–352.

Munari, U., Fiorucci, M., and Moro, D. The Asiago Database on Photometric Systems (ADPS).  Version 2.1. (August 24, 2002).


Keenan, Philip C.  “The MK Classification and Its Calibration.” In Calibration of Fundamental Stellar Quantities, IAU Symposium 111 (1985): 121–136.

Kirkpatrick, J. Davey.  “New Spectral Types L and T.” in Annual Review of Astronomy and Astrophysics, edited by R. Blandford, G. Burbidge, J. Kormendy, and E. Van Dishoeck, vol. 43.  Palo Alto: Annual Reviews, 2005: 195–245.

Morgan, W. W., Keenan, P. C., and Kellman, E.  An Atlas of Stellar Spectra.  Chicago: University of Chicago Press, 1943.

Pickering, Edward C.  “The Draper Catalogue of Stellar Spectra.”  Annals of the Astronomical Observatory of Harvard College 27 (1890): 1–388.

Properties of Stars

Belikov, A.N.  “Stellar Mass Catalogue.”  Bull. Inf. CDS 47 (1995): 9.  VizieR catalog V/85A.

Pasinetti-Fracassini, L.E., Pastori, L., Covino, S., and Pozzi, A.  “Catalog of Apparent Diameters and Absolute Radii of Stars (CADARS).”  Astronomy and Astrophysics 367 (2001): 521.  VizieR catalog II/224.

Perevozkina E.L., Svechnikov M.A.  “Catalog of Eclipsing Binaries Parameters.”  Catalogue of orbital elements, masses and luminosities of eclipsing binaries with detached main sequence components and some results of statistic processing.  Ed. I.I. Bondarenko.  Ekaterinburg, Ural. Univers., 1999.  VizieR catalog V/118.

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