Double in Perseus - Part II

Epsilon Persei (ε Persei)

Struve 471

RA / DEC: 03:57:9 / + 40.01

Magnitude A / B: 2.8 / 8.8

Rho: 8.7”

Theta: 10º

Epsilon Persei is huge. It is young and burning at an extremely high temperature – around 27,000k – giving it that distinctive blue-white hue so common amongst the stars in Perseus. It has a luminosity of about 28,000 Suns, is around 16 times the Sun’s mass and nearly four times bigger. Needless to say, like so many other stars in Perseus, with less than 10 million years of age, Struve 471 in a few million years time is destined to explode into a magnificent supernova.

Around 538 light years from Earth by all accounts Epsilon Persei is a spectroscopic binary meaning that the only evidence of a binary star comes from the Doppler effect on its emitted light. It is also one of the most commonly known exteme variables in the Milky Way which means the absorbtion lines seen on the spectrum are varying rapidly in the space of just few hours.

Nevertheless, for the observer, a small, fainter dwarf companion can be seen with a separation of about 10” of arc, implying that this secondary is at least 1,600 AU from the primary. It is very unlikely that this is a true companion making Struve 471 a line of sight double.

At around 50x the secondary was barely visible but upping the magnification to around 140x greatly improved matters and it was easy to split the very bright primary from the fainter bluish companion.

40 Persei

Struve 431

RA / DEC: 03:42:4 / +33.58

Magnitude A / B: 4.9 / 10

Rho: 19.8”

Theta: 244º

As should be obvious by now, the constellation of Perseus is noted for containing a lot of class B stars probably of which are part of the OB Association. These stars are massive and dying young and many will explode into supernova. In the not too distant cosmic future, the constellation of Perseus will be a new breeding ground for Solar Systems and planets and will probably be as aesthetically beautiful as is M 43 in Orion.

40 Persei or Struve 431 is no different. It is another class B star dimmed only by the huge quantity of interstellar debris and dust between it and Earth. With a surface temperature of around 28,700k and a luminosity of about 23,600 suns, when its hydrogen fusing lifetime is over and its helium core is complete, it will probably become a Super Red Giant, leading to its total collapse and massive explosion as a supernova.

Between 924 to 1055 light years away, 40 Persei is listed as having two companions. A 10^th magnitude optical coincidence 20” of arc away from the primary and a spectroscopically detected neighbour.

At the eyepiece, the optical double was easily split revealing a bright bluish star and a fainter blue companion.

Struve 446

RA / DEC: 03:49:5 / + 52.39

Magnitude A / B: 6.8 / 9.9

Rho: 8.9”

Theta: 254º

Jeweled within the small and sparsely populated cluster of NGC 1444 is Struve 446. Another B type star and probably not part of the cluster which is some 3,330 light years away. Information on this little gem was scant, but as can be seen from the sketch, it really is a very pretty double with the light, golden-yellow primary, and a fainter blue companion easily split at around 100x to 140x. Well worth seeking out.

Struve 268

RA / DEC: 02:29:4 / + 55.32

Magnitude A / B: 6.7 / 8.5

Rho: 2.7”

Theta: 131º

Struve 270

RA / DEC: 02:30:8 / +55.33

Magnitude A / B: 7 / 9.6

Rho: 21.4”

Theta: 305º

Struve 268 is another main-sequence B star about 649 light years away whilst Struve 270 is between 166 to 181 light years away and burning with a mass of about 4 suns. It has been observed that Struve 270 is emitting strong infra-red emissions suggestive of a recent catastrophic collision between itself and some planet or planetary embryo.

What makes Struve 268 and Struve 270 so striking is the fact that they’re both woven into a beautiful, open field of frosted silver, bright blue and white stars. Although Struve 268 was relatively easy to split at around 140x, I preferred to sketch the entire star field which would also include Struve 270 at around 50x. In consequence, Struve 268’s companion appears and is a very tight split at this magnification whereas Struve 270 remains an easy, wide double.

Struve 268 was seen as a relatively bright bluish star with a fainter white companion whilst Struve 270 had a notable yellowish hue to it and its companion was a fainter blue. There is a C and D component for Struve 270 but at around 12^th magnitude I had no luck in spotting them and figured either my telescope wasn’t up for the job or the city’s sky-glow had simply drowned them out.