Family Parties Of Stars

( Originally Published Early 1900's )

THE subject matter of the preceding chapter will naturally suggest the idea that if one naked-eye star is found telescopically to consist really of 2 stars, why not another of 3 stars or 4 stars, or more, in close association physic-ally or apparently? And such, indeed, is the case. We have, accordingly, plenty of triple stars, some quadruples, some quintuples, some sextuples, and so on many of them very picturesque to look at through a telescope. Amongst the triple stars within the easy reach of amateurs armed with small telescopes may be mentioned Flamsteed's 11 Monocerotis, 12 Lyncis, and 51 Librae. The following are quadruples :rr2 Canis Majoris, 82 Lacertae. ß Lyrae is a quintuple. Again there are some stars which comprise so many constituents that they can best be described as " multiples "; such are e Lyrae and o Orionis.

It will be seen from the engravings that each of these exhibits a double system of stars, so that e Lyrae may be called a double-double, whilst o Orionis is a double-triple. The former object comprises one pair of stars of mags. 5 and 6 1/2, whilst the second pair are 5 and 5 1/2 respectively. There seems every reason to suppose not only that the 2 stars of each pair constitute a binary system (each star revolving round the other), but that each pair taken together revolves round the other pair, thus constituting a double-binary, or a system of mutual association of great complexity. Between the 2 main pairs there are several smaller stars. Many telescopes will show 3, and Professor Hall, in America, has made the 3 into 7, but his additional stars are very faint indeed, and can only be seen in the very largest telescopes. e Lyrae is on the frame of the Lyrae, 1 1/2 N. E. of the very bright star Vega.

The group forming o Orionis, whilst it bears a certain family resemblance toe Lyrae, differs from it in the respect that we have no knowledge of any of the stars being linked together so as to constitute a moving system. o Orionis may be easily found, as it forms the southern vertex of a triangle with the 2 last stars (C and e) in Orion's Belt ; and it is rather less than a degree from C in the direction of B.

Orion contains another multiple star of great interest known as B Orionis. In this case there are 6 stars, the four most conspicuous of which make a trapezium at distances not very unequal. The 5th and 6th stars are fainter, and lie just outside the boundary lines of the trapezium. In this case the component stars are not organised in pairs, and do not appear to constitute a system physically connected. Orionis is in the midst of the " Great Nebula in Orion," of which more anon. Perhaps it might even be said to form a part of the nebula.