December 2017 - Double Star of the Month

The two pairs selected for December are both wide, unequal double stars.

WEB 2 (03 42 42.73 +59 58 09.8) appears in the first edition of Celestial Objects for Common Telescopes. In it, Webb calls the primary star P III 97 and in examining Piazzi's Palermo Catalogue you will find that Piazzi did indeed record the primary star and also the secondary. He adds a note saying another telescopic (star) follows to the north, so this is, in fact, a discovery by Piazzi.

Webb was almost certainly drawn towards this star because of his abiding interest in red stars. His notes say orange with scarlet blaze and bl(ue). for the colours of the components which is a good enough reason to observe this pair.

The magnitudes are 5.7 and 8.9 and the current position of B is 33° and 54 arcseconds but there is no evidence that the stars are are in any other way connected. Espin added two fainter, closer stars in PA 33° and 98° and there is an 11.8 magnitude at 168 arcseconds along PA 162°.

WEB 2 is close to STF 385, STF 389, STF 396 and STF 400, 15 degrees due north of Mirfak (alpha Per).

H 3 80 (02 26 00.38 -15 20 28.0) is in Cetus in a fairly sparse area of sky about 12° south of Mira, 1.5 degrees preceding σ Ceti towards τ Ceti.

Herschel came across this pair on October 13th, 1782. He measured the distance as 11.2 arcseconds and the PA at 292°. There has been little change in either coordinate since then.

The stars are magnitudes 5.9 and 9.1 and the primary is a A star although William Herschel called it reddish white, whilst the companion appeared bluish-red to him.

The primary star (AB Ceti) is both a spectroscopic binary and a member of the Alpha2 CVn class of variables. These are main-sequence stars which display strong magnetic fields and whose spectra show abnormally strong lines of Si, Sr, Cr, and rare earths. They exhibit magnetic field and brightness changes and the amplitudes of the brightness changes are usually no greater than 0.1 magnitude in V.

Bob Argyle - Double Star Section Director