Searching out new double stars is kind of like looking at a map and wondering what things are like over the horizon. And if you look often enough, eventually you find that gem that causes you to melt slowly into your chair.
Like Beta (β) Monocerotis.
This one ranks right up there at the top of the list of stellar beauties scattered across our night sky. Although it’s been lurking in the back of my mind for some time, I’ve basically ignored the impulse to track it down. But I did finally get to it. And seldom has a star had the effect this one did. I’ll never forget when, where, or with what I first saw it.
But first — as they say in the real estate business — let’s talk about location!
I think I can safely say that Monoceros (as in Mo-NOS-er-os) is not a name that rolls off your tongue quickly. Which is probably because you don’t visit it frequently — or ever. Of course, it doesn’t help that its brightest star, Beta (β), sits up there with a rather dim magnitude of 3.92. And surrounded as it is by its more famous neighbors — Canis Major to the south, Gemini to the north, and Orion to the west — it’s not surprising that it’s so easily overlooked. Although with Hydra to its east, at least it has a neighbor with which it shares the misfortune of being unfortunately unknown. The ultimate description of this non-bright constellation of stars comes from Jim Kaler: “one that looks nothing like anything.”
On the other hand, you would think that the only Unicorn in the sky would get more respect than this one gets. It does have some rather attractive attractions, after all. In addition to laying claim to stellar fame with Beta (β), this land of the Unicorn is home to a pair of well known deep sky objects, the Rosette Nebula and the Cone Nebula. And with the winter Milky Way running through it, it has more than its share of open clusters, including one Messier object, M50. For more on Monoceros, see Jim Kaler’s “Riding the Unicorn.”
All of the stars we’re going to take a look at on this map tour are on the western edge of Monoceros, near the border with Orion, and are lined up along a line running from north to south. In fact, they’re within about five minutes of each other in right ascension. I didn’t try it because I was using an alt-az mount most of the time, but if you ever wanted to experiment with setting circles (the real ones, not digital!), this would be a great place to do it. Starting with our first star, Epsilon (ε), use the declinations listed below for each star, and move your scope south to each of them and see how close you can come. You can’t wander too far off track in this case!
So — Epsilon (ε) is where we start. It’s an easy one to find. In fact, so is Beta (β). Looking at the chart below, start with Procyon in Canis Minor and draw a line to the southwest to second magnitude Saiph, at the lower (southeast) corner of Orion. Along that line, you’ll see Delta (δ) and Beta (β) Monocerotis spaced at equal distances. But we’re going to Epsilon (ε) now, not Beta (β), so at Delta (δ), draw a line to the northwest to reddish-orange Betelgeuse, and you’ll find Epsilon (ε) about two-thirds of the way along it.
Epsilon (ε) Monocerotis (Σ 900) (AB is H III 29) HIP: 30419 SAO: 113810
RA: 6h 23.8m Dec: +04° 36′
Magnitude A: 4.4 B: 6.6 C: 12.7
Separation AB: 12.3″ BC: 91.8″
Position Angle AB: 31° (WDS 2011) BC: 254° (WDS 2008)
Distance: 128.5 Light Years
Spectral Classification: A5, F5 (A and B)
I celebrated the first evening of February (Groundhog’s Day Eve, as I’m sure you know) by pointing my six inch f/10 refractor at this little gem, using an 18mm Tak LE (84x). In Double Stars for Small Telescopes, Sissy Haas describes this as a showpiece in a 60mm scope — and I can confirm that because I took a quick look at it in the 60mm f/13.3 I have attached to the six inch scope. But the view in the larger scope pulled me — no, yanked me — away from the 60mm. At low magnifications, this one is really an attractive, close pair of stars.
Color-wise, what I saw was a yellow-white primary and pale white secondary that seemed to have a trace of orange in it at times. The 12.7 magnitude “C” member of this trio hangs out there to the southwest all by itself and is a bit too faint, to say the least, to detect any color. But I’ll gladly yield to Haas’s description of the color of the other two stars: “A brilliant white star almost touched by a silvery smokepuff.” And she credits Admiral Smyth with “golden yellow; lilac.” Hmmm — can’t say I’ve ever seen lilac in a star. Have you?
I returned to Epsilon (ε) on February 8th (this time celebrating the first Tuesday after Groundhog’s Day Eve) with a Celestron 102mm f/10 refractor and a 25mm TV Plossl (41x), and I have to say this was the best view yet. At that magnification, they were a rather close pair, gleaming like a pair of jewels against the backdrop of the black sky. Not a bad start — or a bad star — for an anonymous sector of sky.
Σ 910 HIP: 30670 SAO: 113892
RA: 6h 26.7m Dec: +00° 27′
Magnitudes: 7.0, 8.1
Position Angle: 153° (WDS 2002)
Distance: 739 Light Years
Spectral Classification: G5
OK, for those of you — and I’m certain there are hundreds — using their setting circles, we now move south four degrees in declination. Or, if you’re star hopping like I am, use the chart shown here and, from Epsilon (ε), move south about two degrees to 5.6 magnitude HIP 30728, and then move another two degrees south to a pair of stars of similar brightness, 5.2 magnitude HIP 30717 and 5.6 magnitude HIP 30720. And you’ll find Σ 910 just to the north and slightly west of this pair. Now if you are using your declination circle to find this one, I can almost guarantee you’ll find it quicker than I did. It took some poking around before I came up with it because it wasn’t quite where I thought it was. So don’t under-estimate the “old ways” — they still have their advantages!
I found this pair particularly intriguing and interesting because of the surrounding field. Along with Σ 910, there are four pairs of stars in the field — a close pair to the south, a little less close pair to the west, and two almost parallel pairs to the north — none of which, from what I can determine, are identified as double stars.
So to return to Σ 910, once again I saw a yellow-white primary, while the secondary appeared blue with some gray in it. Haas notes that Webb saw yellow, and Smyth saw “topaz yellow and plum tinge.” OK — first he sees lilac, and now plum. Wonder if he was wearing glasses with tinted lenses? Maybe I need to work on some poetic color descriptions: how does dandelion yellow and metallic gray strike you for Σ 910? No? I don’t suppose you would be real thrilled with egg-yolk yellow, either, then.
Anyway, the color continues to the southwest in this field. The first star to the southeast of Σ 910 I noticed was reddish-orange in color, and the next one to the southeast of it was a subtle bluish white.
And now on to the star of the show.
Beta (β) Monocerotis (Σ 919) HIP: 30867 SAO: 133316
RA: 6h 28.8m Dec: -07° 02′
Magnitude A: 4.6 B: 5.0 C: 5.4
Separation AB: 6.9″ BC: 2.8″
Position Angle AB: 133° BC: 108° (Data for AB and BC are WDS 2011)
Distance: 691 Light Years
Spectral Classification: B3 for all three components
Where I was when I first saw this was on my deck at about 2AM on January 22nd with an Astro-Tech 72mm refractor. A front had blown through a few hours earlier and left huge, fluffy white clouds frantically fleeing to the east under almost blue skies that were bright because of a third quarter moon sitting up high in the northeast. The transparency was fan-tastic. And, as you would expect in the wind, the seeing was somewhere south of horrible. But you can tolerate a lot of poor seeing in a small refractor with a short 430mm focal length because it tends to limit your magnification.
I had just taken a quick — which turned into a long — look at Mizar, and was amazed at how white the stars appeared against the backdrop of that almost blue sky. I’ve never seen it like that — I was riveted to the eyepiece for a good twenty minutes. It was then that I finally remembered Beta (β) Monocerotis. So I grabbed my Sky and Telescope Pocket Atlas, located it, looked to the south, aimed the scope, and found Beta (β) looking back at me in the eyepiece.
But just two stars, not three. I worked my way up through several eyepieces and had expected to finally split it with a 5mm Tak (86x). Actually, I don’t know what I expected since I had never seen it. But the 5mm Tak wasn’t doing it either. Several times one of the two stars looked like it was trying to pull apart, but I wasn’t even sure which of the two should split. So into the diagonal went a 4mm AT Plossl, which jumped me up to 108x — quite a bit of magnification for a 72mm f/6 scope, in poor seeing no less — and son of a stellar gun, I was looking at three stars.
Now — just not any three stars. But three very white stars —- all very similar in size —- with two of them very, very close together. The view of those three white beads of light, accentuated by the contrast with that bright, moonlit sky is —- well, to quote William Herschel —- “One of the most beautiful sights in the heavens.” When I saw those two stars split and spread apart, I felt an electric thrill run through me that was set in motion by photons which had steadily been making their way to meet my eyes —- for six hundred and ninety-one years. Now think about that for a minute or so — it deserves at least that much thought.
I was standing at the time, and I clearly remember muttering several things that can’t be included here, and dropping down onto the seat of my observing chair, and simply not moving for about thirty minutes except to touch the slow motion controls. Seldom has a view affected me like that. This is really one of THE most amazing, thrilling, unbelievable, indescribable, unlikely sights in the sky. A triple star is always a nice sight, but three stars of the same brightness and the same color, all closely spaced in a very small segment of the field of view, and two of those incredibly close together and yet clearly separated into distinct round globes?
Words just don’t do this justice. Because they can’t. You feel this one, you don’t describe it.
I’ve been back several times — with a six inch f/10 refractor, a 102mm f/10 refractor, a pair of 60mm f/16.7 refractors, and again with the 72mm refractor last night in fog so thick I could barely see it. And I’ll be back again and again and again. I’ll hunt this one down through tree limbs, through sucker holes, through haze and murk — and I’ll keep going back for more.
Σ 914 (H III 43) HIP: 30675 SAO: 133263
RA: 6h 26.7m Dec: -07° 31′
Magnitudes: 6.3, 9.3
Position Angle: 299° (WDS 2010)
Distance: 409 Light Years
Spectral Classification: A0
I came across this one a few days after being stunned into a stupor by Beta (β). It’s listed on p. 105 of Sissy Haas’s book, and she says there that it’s “easily noticed in the field with Beta Monocerotis.” But I sure hadn’t seen it.
So when I went back a week or so later with the 102mm f/10 refractor, I made a point of trying to find it — and sure enough, it’s there, but you have to go looking for it. It won’t reach up through the eyepiece and grab your nose. Using a 14mm Radian (73x), which gave me a field of view of eight tenths of a degree, I found that if I put Beta (β) in the northeast corner of the eyepiece, Σ 914 was just visible at the southwest corner. I repeated that again with the two 60mm scopes using a 17mm Plössl (59x) that provided a field of view .85 of a degree.
In the four inch scope, both components were easy to see. With Beta (β) in the field, they really are a picturesque picture. In the 60mm scopes, though, I needed averted vision to pick out the 9.3 magnitude secondary from the glare of the white primary, which is about sixteen times brighter. Haas comments that this pair looks wider than 20.7″, but I think the contrast in separation with Beta (β), combined with the differences in brightness, tends to make them look wider than they actually are.
So — now you can say you’ve been to meet the Unicorn, aka Monoceros. And I don’t know about you, but I’ve already got plans to go back. There are more than a few double stars lurking around the edges of many of its Monocerotic clusters.
Before I wind this one up, I was asked by a new neighbor behind me what the heck I was doing out on my deck under a cold dark sky at two in the morning. Trying to explain it in terms he could understand was hopeless. He knows where the sun is in the daytime, and if pressed, he could find the moon if it was out at night.
So after about twenty minutes of talking past each other, he finally said, “Well, I guess it beats watching grass grow.”
I thought a few seconds, and I finally said, “All grass does when it grows is creak and squeak. But starlight activates something deep inside me.” And then I saw a glint of curiosity in his eyes.
Hope your skies are clear!