2-1 Looking Deeper into Astronomy Star Names and Catalogs

he customs for naming stars have changed over the As you might suspect, memorizing exotic star names is an centuries. Many of the brightest stars in the sky have unwelcome burden for many astronomers. A simpler system, TArabic names that were assigned in medieval times, invented by Johann Bayer in 1603, uses the constellation when astronomy was widely studied among Islamic nations. names and the 24 lowercase letters of the Greek alphabet: The illustration shows the Big Dipper with the Arabic names for its seven brightest stars. The North Star received its formal name, Polaris, later, when Latin was the language α alpha i iota ρ rho used by European astronomers. β beta κ kappa σ sigma γ gamma λ lambda τ tau δ delta µ mu υ upsilon Polaris ε epsilon ν nu φ phi ζ zeta ξ xi χ chi η eta ο omicron ψ psi θ theta π pi ω omega

In constructing a star name, a Greek letter is used with the Latin possessive form of the name of the constellation in ␨ Mizar which the star is located. In most cases, the brightest star in the constellation is , the second brightest is , the third is , and so ⑀ α β γ Alkaid on. For example, the brightest star in Libra (the Scales) is called Alioth ␦ ␣ Megrez Dubhe α Librae, or α Lib for short. This name is more informative, if less melodious, than its Arabic name, Zubenelgenubi (meaning ␥␤ “scorpion’s southern claw”). The 12 constellations of the Phecda Merak zodiac with their Latin possessives are as follows: Constellation Possessive astronomer whose widow financed the project.) The 225,300 stars in this catalog are listed by their HD numbers. Aries Arietis For example, HD 87901 is α Leonis (also called Regulus), Taurus Tauri the brightest star in Leo (the Lion). Gemini Geminorum The most extensive catalog of stars yet compiled is the Cancer Cancri Hubble Space Telescope Guide Star Catalog. This is an Leo Leonis immense list of 15,169,873 stars, all too faint to be seen by the Virgo Virginis naked eye, whose positions are used to help in pointing the Hubble Space Telescope (see Figure 1-3 on page 4 of Libra Librae Universe). Stars from this catalog have GSC numbers, such as Scorpius Scorpii the star GSC 1234 1132 in the constellation Taurus. Unlike Sagittarius Sagittarii other star catalogs, this one is only available in electronic form Capricornus Capricornii (on two CD-ROMs); if it were to be printed, it would require Aquarius Aquarii hundreds of thousands of pages. Pisces Piscium There are many star catalogs, including some that list only stars of specific types. As a result, a single star may have a In Bayer’s system, only the brightest two dozen stars in a plethora of different names. For example, the bright star constellation can be named. However, astronomers are often Vega in the constellation Lyra is also known as α Lyrae, interested in very faint stars, many of which are too dim to be BD +38° 3238, HD 172167, 3 Lyrae, HR 7001, GC 25466, seen with the naked eye. Astronomers refer to these fainter SAO 67174, and ADS 11510. In this book we use the Bayer stars by using designations from standard star catalogs. system in most cases and thus will refer to this star simply One of the first major star catalogs, Bonner Durchmusterung as “Vega (α Lyrae).” (Bonn Comprehensive Survey), was produced in Germany in the TIO AU N! A number of unscrupulous commercial firms offer to C mid-1800s by F. W. Argelander of the Bonn Observatory. This name a star for you for a fee. The money that they charge catalog lists the positions of 324,188 stars, each of which is you for this “service” is real, but the star names are not; designated by a BD number. For example, the star BD+5° 1668 none of these names are recognized by astronomers. If you is a dim star in the constellation Monoceros (the Unicorn). want to use astronomy to commemorate your name or the Another frequently used catalog is the Henry Draper Catalogue, name of a friend or relative, consider making a donation to which was compiled in the United States between 1911 your local planetarium or science museum. The money will and 1915. (It is named after a physician and avid amateur be put to much better use!