Double Stars

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=22 BGCOLOR="#330099" TEXT="#080000" bgproperties="fixed" background="040000d2erkqrf.gif"> <div> Derby and District Astronomical Society - Aries Magazine</div> <div> </div> </td> </tr><tr> <td valign="top" width=145 BGCOLOR="#333399" TEXT="#080000" background="03fa2c00erkjzj.gif"> <div> <A HREF="index.htm" TARGET="_top" TITLE="Aries Astronomy magazine on line Derby a"><U>HOME</U></A></div> <bR> <div> <A HREF="editorial.htm" TARGET="_top" TITLE="Aries on line Autumn 2000 editorial"><U>Aries on line - Autumn 2000 editorial</U></A></div> <div> <B>Double Stars</B></div> <div> <A HREF="id25.htm" TARGET="_top" TITLE="Pluto and Back for bed"><U>Pluto and Back for bed</U></A></div> <div> <A HREF="vla.htm" TARGET="_top" TITLE="VLA Radio telescope"><U>VLA Radio telescope</U></A></div> <div> <A HREF="id27.htm" TARGET="_top" TITLE="Beginners nebulae"><U>Beginners - nebulae</U></A></div> <div> <A HREF="id28.htm" TARGET="_top" TITLE="Forgotten Astronauts"><U>Forgotten Astronauts</U></A></div> <div> <A HREF="id29.htm" TARGET="_top" TITLE="Sky Scene Oct Dec 2000"><U>Sky Scene Oct - Dec 2000</U></A></div> <bR> </td> <td valign="top" height=458 BGCOLOR="#FFFFFF" TEXT="#080000" background="06a92963.gif"> <div> <I>Aries Astronomy magazine on line- Derby and District Astronomical Society</I></div> <div> <IMG SRC="04107040.gif" border=0 width="263" height="4" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> In Praise of Double Stars</div> <div> <I><B>Author: Steve Parkins</B></I></div> <bR> <div> One of the more neglected areas of astronomy in recent times has been the observation and study of double or `binary` stars. In these days of the pointless domestic security light and all pervasive sodium streetlight glow (Phew! I feel better now) the observation of doubles from a city centre location is probably one of the least affected aspects of amateur astronomy. Forget visual deep-sky observing from where I live, apart from the usual tourist attractions, without narrow band filters.</div> <div> The contrast between two or even more stars in close proximity to each other brings out the subtle colour tones that would normally be lost if each were viewed in isolation. At any star party where attracting members of the public is the main aim then showing them a star such as Albireo (Beta Cygni) always brings oohs and ahs from the uninitiated. Double stars give an instant reward to the observer of any experience. The variable star aficionado must wait days, months or even years to see appreciable change on what, on any given  night , is just a star unless they are into things like cataclysmic variables The planetary observer needs experience and a trained eye to fully appreciate the marvels of planetary detail and the deep sky observer is fighting an ongoing battle against light pollution throughout the country.</div> <bR> <div> Despite this, all the topics I have just mentioned are essential ingredients in this great pursuit of ours but I believe that double star observing gives the most immediate return for the younger or more inexperienced observer who's interest  is perhaps not yet a foregone conclusion and must be nurtured and not put off by bad observing experiences. Once bitten by the astronomy bug  all other aspects of the subject such as mentioned above become available.</div> <bR> <div> There are several types of double stars:-</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Optical doubles. These are merely line of sight effects between two stars that appear to be close  in space but in reality are not. Who knows on some distant planet around another star our own  sun may appear as a fine `optical double` alongside some other star of which we can only guess.</div> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Visual binaries consist of two or more stars that are certainly related and orbit their common centre of gravity.</div> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Spectroscopic binaries have components that are so close together only by means of analysing their spectrums can the fact they are multiple be proved.</div> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Astrometric binaries may be observed similar to visual binaries but are much less obvious and were usually discovered by means of long timescale study of a stars apparent movement much  like it was hoped actual planets of other  stars might be found.</div> <bR> <div> William Herschel, as with so many other aspects of astronomy, is credited with proving that stars can exist in a gravitational relationship with each other. A series of observations around the year 1803 proved this, although stars such as Mizar and the Trapezium in Orion were discovered much earlier. Other well known contributors to our knowledge of binaries were William Smyth and the Rev. W. R. Dawes in England and Wesley Burnham (of catalogue fame), in America. Friedrich Struve compiled an extensive catalogue  from which many doubles obtain their designation. A double denoted by the greek letter `sigma`  and a number show it appears in his work published in 1837. </div> <bR> <div> Here are just a few fine doubles to look for over the summer months :-</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">As already mentioned , Albireo is a fine bright double of gold and blue or is it yellow and sea green? Decide for yourself.</div> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Eta Bootis is not as bright but compare its yellow/blue tones with the above.</div> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Alpha Herculis,  reddish/orange and green.</div> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Gamma Delphini, fine greenish/yellow pair.</div> <div> <IMG BORDER="0" SRC="Symb075c00b7011899003300.gif" HEIGHT="19" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Epsilon Lyrae , the famous double-double star north of Vega. Its components lack any hue but it is the most accessible example of a quadruple star.</div> <bR> <div> For an extensive range of double stars the <A HREF="http://www.webbsociety.org" TARGET="_top" TITLE="http://www.webbsociety.org"><U>Webb Society (Internet site at – www.webbsociety.org)</U></A> have published a catalogue called A Visual Atlas of Double Stars  which is very good for the beginner and easy to use at the telescope. They also produce an Observers Handbook Vol. 1, Double Stars. I am not sure if this second book is easily available. I had to really search for my copy but eventually obtained one at  AstroFest but is a splendid book on the subject. Also never forget the range given in Norton`s Star Atlas. </div> <bR> <div> Further Internet reference for binary star systems: <A HREF="http://www.h2g2.com/A381124" TARGET="_top" TITLE="http://www.h2g2.com/A381124"><U>http://www.h2g2.com/A381124</U></A></div> <bR> <bR> </td> </tr></table></body>