After spending a nerve-wracking and ghoulish evening carousing with Algol and its companions a few weeks ago, I turned my attention to perusing its specterous neighborhood for other interesting stellar objects that might be lurking in the darkness. And that’s when I discovered a little know interstellar highway which goes by the name of The Algol Road.
In order to locate this starlit road, all you have to do is extend a line east from Algol to Epsilon (ε) Persei, a 2.89 magnitude blue-white star that occupies the road’s opposite end, where it competently guards Perseus’ eastern approaches. Epsilon (ε) is a tricky little triple star, but before reaching it, you’ll trek past two other immensely intriguing multiple stars. The first stellar distraction to be found along The Algol Road is Σ 369, an attractively tight seventh magnitude pair. The second scenic attraction is the odd-prefixed AG 67, a uniquely aligned triple star in a stunning field of near matches.
So toss a few eyepieces into your traveling bag, grab a warm coat, and hop aboard my star-dusted traveling machinery – our first stop is a mere 705 light years away.
Σ 369 HIP: 15282 SAO: 38700
RA: 03h 17.1m Dec: + 40° 29’
Magnitudes: 6.83, 7.72
Position Angle: 29° (WDS 2010)
Distance: 705 Light Years
Spectral Classification: B9, A0
Now there are two ways to get to our first star.
First, you can start at Algol and traverse the highway for a distance of about two degrees due east. Or, if you’re new to these parts, you can cheat a bit and use Rho (ρ) and Omega (ω) Persei as pointers. If you draw a line from the first one (ρ) through the second one (ω) and then divert it very slightly to the north and extend it again for the same distance, you’ll find yourself passing over the top of 7.0 magnitude HIP 15065 and landing right on target at our first destination, Σ 369. In fact, if you’re using an 8×50 or 9×60 finder, I recommend you pause and linger over this view for a few minutes. Algol, Rho (ρ), Omega (ω) and Σ 369 will all fit quite comfortably into your finder field of view — add them together and you have a very satisfying configuration of starlight.
But of course we came here to pay Σ 369 a visit, so when you’ve had your fill of lingering, we’ll break out an eyepiece that will deliver something on the order of 100x for our six inch refractor and see what we can see.
This is a tight pair – no surprise given its 3.4” separation – but since the two stars are within a magnitude of each other, they’re not difficult at all to pry apart. In fact, the first time I saw them was in my 80mm f/15 Mizar refractor in very poor seeing conditions – so poor, in fact, I never was able to apply enough magnification to split the pair, but I did eke out a a hint of duplicity. In a refractor, they have that classic pin-hole-in-black-velvet-appearance which is so characteristic of two closely spaced stars of similar magnitudes.
And they’re a pleasing white pair of stars as well, although in his comprehensive survey of Struve’s stars, Thomas Lewis described the secondary as “ash.” (p. 87 of this book). Haas describes them as a “bright white star with a shadowy greenish spot almost touching it” – but when I asked the shadowy Mr. Green about that, he said he had never been there. (This is Mr. Green: ➡ :mrgreen:)
Surprisingly, William Herschel seems to have missed this pair, but the senior Struve did happen across them in 1829. In his initial observation, he recorded a separation of 3.25” and a position angle of 28.8 degrees, both of which are generally echoed by later nineteenth century observations, as you can see in the thumbnail at the right from the Lewis book. So given the 2010 Washington Double Star (WDS) figures of 3.4 arc seconds of separation and a position angle of 29 degrees, the primary and secondary have barely moved at all in relation to each other in the intervening 181 years.
Let’s move east now to a very rare view. The best way to get where we’re going is to draw a line from Algol to our present Σ 369 location and then extend it further east by the same distance. In your finder, that will bring you out just short of two faint stars, 7.0 magnitude HIP 16186 and 6.7 magnitude AG 67.
And be ready for a surprise.
AG 67 HIP: 16220 SAO: 38870
RA: 03h 29.0m Dec: +40° 11’
Magnitudes AB: 7.49, 10.37 AC: 7.49, 11.10
Separations AB: 23.80” AC: 52.60”
Position Angles AB: 349° (WDS 2002) AC: 351° (WDS 2009)
Distance: 673 Light Years
Spectral Classification: G5 (A only)
(AG is Astronomische Gesellschaft)
Now I really had to look twice when I first cast eyes on this field because there were two very obvious clusters of stars competing for my attention:
AG 67 is supposed to be the featured attraction in this sketch, but it’s surrounded by a lot of other attractive company, too.
First, there’s seventh magnitude HIP 16186 and its two attendants at the west edge of the field, which really confused me until I grabbed my notes and pinned down position angles. Then there’s a curving trio of tenth and eleventh magnitude stars several arc minutes northwest of AG 67, plus a very tight triangle of twelfth magnitude stars northeast of those that make themselves known as a difficult-to-resolve shadowy presence. I can’t recall ever seeing anything quite like this field of stars, mainly because of the similarity between AG 67 and HIP 16186. And as you can see in the condensed view in the photo below, this is a field rich in galaxies, although I didn’t see any of them — the brightest one in the field was well out of my reach at fifteenth magnitude.
AG 67’s 7.49 magnitude primary struck me as white, but surprisingly I found more color in the midst of HIP 16186’s retinue. Although that star was an intense white, I was able to detect a very subtle blue hue in the 10.2 magnitude star southwest of it (to the right in the sketch).
Last, but hardly least, is Epsilon (ε), also a triple, situated at the end of the Algol Road.
Epsilon (ε) Persei (Σ 471) (AB is H II 22) (D is ARN 59)
HIP: 18532 SAO: 56840
RA: 03h 57.9m Dec: +40° 01’
Magnitudes: AB: 2.85, 8.88 AC: 2.85, 13.90 AD: 2.85, 9.25
Separation: AB: 8.70” AC: 79.90” AD: 162.90”
Position Angles AB: 10° (WDS 2008) AC: 10° (WDS 2009) AD: 146° (WDS 2003)
Distance: 538 Light Years
Spectral Classification: “A” is B0.5, “B” is A2, “C” is K7, and “D” is A5
To quote my notes, what we have here is a “blazing beauty.” I saw all white everywhere I looked (lots of it), but Haas saw a “brilliant whitish lemon star almost touching a little dot of rich cobalt blue” in a 125mm scope at 200x. On page 91 of The Bedford Catalog, Admiral Smyth described Epsilon (ε) as a “fine and delicate object” and saw pale white and lilac in his 5.9 inch Tulley refractor. Lewis recorded “greenish white, blue” (p. 104 of the earlier link), and . . . . . . .
. . . . . . . the star’s discoverer, William Herschel, described it as “w.” [white] and “d.” [dusky] when he first looked at it on August 2nd, 1780, at a magnification of 222x. (1782 Catalog, scroll halfway down to “Catalogue of Double Stars”)
When I looked at Epsilon (ε), the 9.25 magnitude “D” companion (the third star referred to above by Herschel) stood out rather well in this sparse field, but the 13.9 magnitude “C” sibling was absolutely nowhere to be seen.
It’s far enough out there, at 79.9 seconds of arc from the primary, that it should be visible in a six inch refractor — and at the same position angle as “B”, I really expected to see it. The seeing on this particular night was horrible, though, so I had no luck trying to penetrate the evil veil of scattered light drawn over it.
Epsilon Persei “A” has the distinction of being one of the hottest stars in the sky visible to an unadorned eye. It burns at a “mere” 27,600 Kelvin (49,220 degrees Farenheit), which means it’s about 5.5 times hotter than the sun (5800 K., or 9980 F.) Size wise, compared to our nearest star, the radius of Epsilon “A” is seven times greater than the sun, and it exceeds the sun in mass by a factor of fourteen. Add all that up and what you have is a star racing toward supernovae status in a few million years.
So time’s a wastin’ – you better get out there soon and take a look at this blazing beauty.
Clear Skies! 😎