As the long twilight of a summer evening slowly yields to darkness, if you face south and cast an eye high up into the sky west of Vega, you’ll find yourself looking at the familiar keystone asterism at the center of Hercules. Halfway between the southeast corner of it and Rasalagethi, you’ll find a fairly unremarkable looking whitish third magnitude star that’s about where Hercules’ left (eastern) knee should be — except that it’s really Hercules’ right shoulder because the poor guy is situated with his head pointing south towards Ophiuchus, not north.
But — if you point a telescope of eighty millimeters or more at Delta (δ) Herculis on a dark, moonless night, you’ll find yourself looking into the center of two concentric rings of white stars with a glowing ball of whitish light and just a dot of a secondary sitting in the center.
And … it … is …. …. …. magnificent!
Delta (δ) Herculis (Σ 3127) HIP: 84379 SAO: 84951
RA: 17h 15.0m Dec: +24° 50′
Magnitudes AB: 3.1, 8.3 AC: 3.1, 10.5 AD: 3.1, 10.6
Separations AB: 12.3″ AC: 173.8″ AD: 191.6″
Position Angles AB: 288° (WDS 2010) AC: 357° (WDS 2009) AD: 93° (WDS 2009)
Distance: 78.5 Light Years
Spectral Classifications: A3 for each component
What struck me on my first look at Delta (δ) was how bright the field of view is. The white light of the primary, at a magnitude of 3.1, is the chief cause of that impression, but it’s helped quite a bit by the north edge of the outer ring of stars, which are almost a full magnitude brighter than those in the inner ring. (You’ll notice the outer ring is not quite complete, but like a lunar crater missing a part of its rim, your imagination easily fills in the gap). Adding to the brightness of this image is the glow in the inner ring which is contributed by the gleaming primary. And the final touch to this impression of a ring of fire is that most of these stars are barely varying shades of white.
I’ve included both a photo of the area, as well as a sketch, in hopes that you can mentally put the two together and get some idea of the effect of this configuration of stars. The photo is a bit misleading because it includes fainter stars than you’re likely to see, and it loses some of the effect of the outer ring, but it does show the glow within the inner ring rather well. The sketch at the right is a better rendition of the configuration of the stars that your eyes will actually see. Missing is the silence of the view, along with an intangible quality which was alive at the eyepiece — a quality that words simply cannot begin to touch.
Below is a more recent sketch, which very effectively captures the glow emanating from the primary. When you narrow the field to the point where the outer circle of stars is right at the edge of the eyepiece field of view, the effect can be both very hypnotic and overpowering:
As you can see from the STScI photo and the two sketches, there is a lot of light here competing for your attention. After your eyes have roved around the field of view for a bit, if you can get them to settle at the center, take a long, hard look at the two stars that are the main attraction. I’ve described the primary as white, but there actually is a very slight touch of yellow in it, enough to soften some of the harsh light just a bit. The secondary is a mere point of much paler white light, but it’s nestled up very closely to the primary, and depending on what aperture and what magnification you’re using, you may have to look very closely to see it at first. The spacing between these two stars, and the physical appearance of the secondary in relation to the primary, is very similar to Polaris.
Now no matter how long I spend looking at double stars and reading the literature about them, I’ll never cease to be amazed at the variety of colors other people see. Haas saw the primary as “Sun yellow” and the secondary as “whitish powder blue.” But at least we’re reasonably close, especially in comparison to Admiral Smyth’s description of “greenish white” and “grape red.” I don’t know what to say about that, except that I sure would have liked to have had an hour or two with that 5.9″ refractor he used.
There are two more companions, “C”and “D,” which can be found lurking in the inner ring, both of which are apparently optical only, meaning not gravitationally linked to the primary. The primary itself is actually two stars separated by a mere .06 of an arcsecond, requiring far more sophisticated equipment to detect than most of us have ever dreamed of using. More along these lines can be found in Jim Kaler’s description of Delta Herculis.
As for the equipment most of us are more likely to possess, I’ve found the ideal aperture for Delta (δ) is about four inches. My first view of it was in a 102mm Celestron f10 refractor using an 18mm Radian (56x), and it was perfect for capturing the full visual impact of all that white light which invades the field of view. To get the full effect of both the inner and outer circles, use a magnification that puts the north edge of the circle almost at the edge of your field of view while Delta “A” and “B” are at the center. As you increase the magnification and narrow the field, you begin to lose some of that impact, so don’t get too carried away unless you want to create a driving lane between the primary and secondary — which is well worth the effort if seeing conditions permit.
For a visual challenge, try a 60mm refractor — I found an f15 version would provide just a glimpse of the secondary at 45x, using a 20mm TV Plössl, which is pretty similar to what you would see if you were looking at Polaris. The main difference is the Polaris primary has a distinct yellow tinge to it, whereas the Delta primary shows far more white. Or at least it does unless you happen to be peering into Admiral Smyth’s 5.9″ refractor.
Now the cumulative visual impact of all this white light populating my eyepieces and saturating my sight was a bit of philosophical reflection about their attraction, as well as some thought about what these stars truly are.
What they truly are is a vast assemblage of nuclear furnaces — something Greg has pointed out numerous times. They may not look the least bit lethal from your perch behind a scope, but if you ventured too close to any one of them, the result would be quite a bit more than singed eyebrows or fried fingers. The indisputable fact of the matter is these beautiful stars and their immediate surroundings are tremendously harsh environments. But — as frequently happens when I bend over the eyepiece and focus my eyes on these unimaginably violent objects that I see as bright or dim points of light, my aesthetic experience of them is far removed from the physical and objective reality.
While words are fine for describing the physical aspects of these stars, they don’t work well for describing the aesthetic experience. I’ve half jokingly, half seriously, used the phrase “nourish your neurons” in hopes of getting at the inner depths of what happens within us — yet it still doesn’t quite convey its essence. Something essential, something that reaches very deeply into our present, into our past, and into the very core of our being, takes place. It’s not quite accurate to describe it as mystical, because it’s real — it’s just that it happens outside of language. A far better descriptive word for what takes place is ineffable.
So it comes down to this:
There’s a very definite division between describing the objective physical facts of what we see, and conveying the full subjective impact of it. And yet ….. the two experiences are inseparably intertwined with each other. Together they make possible what we experience, an experience as various as the number of people on this unique planet who peer into eyepieces.
There’s a paradox hard at work here, which is this: these stars are both physically lethal and aesthetically beautiful at the same time. And there’s a miracle here as well, which is the mere chance that any one of us happens to be in the right place and time to intercept those few photons which trigger this difficult to describe aesthetic experience. The paradox was described almost a hundred years ago by Ranier Maria Rilke in his First Duino Elegy: “For beauty is nothing but the beginning of terror, yet still we endure it; and it dazzles us so because it scorns to calmly destroy us.” A bit severe perhaps for our purposes, but only because of the distances involved. But it does convey the paradox rather well.
And that leads to the rousing conclusion of this discussion of the nature of stellar attraction:
There is a reason the chicken crossed the road. He was curious. And so am I. But in my case the road is metaphorical — so I won’t get run over, I won’t singe my eyebrows, and I won’t fry my fingers. Which is fortunate, because I’m drawn to these pinpoints of light like a moth is to a flame — or in my case, multiple flames.
So if you’ll excuse me now — and pardon the digression into aesthetics and philosophy, and chickens and moths — I have to get over to the hardware store and pick up that pair of flame resistant gloves and the welding goggles I ordered — just in case. 😎
Safe and Clear Skies!