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Treasures in Triangulum

The Triangle constellation may be small, but it’s packed with a wealth of worthwhile targets.
ChapleGlenn

As an avid angler, I prefer small ponds over large lakes and reservoirs. Fishing a large body of water can be a daunting task. With hundreds of acres to explore, I could never cover all the hot spots in a day’s time. A 5- to 10-acre pond, on the other hand, can be easily covered in a matter of hours.


It’s the same situation when I switch from fishing to observing. I prefer to “paddle around” a small constellation like Delphinus or Lyra, rather than ride the high seas in a vast stellar aggregation like Virgo or Ophiuchus. With that in mind, let me invite you to one of the night sky’s smallest “ponds,” Triangulum, whose 132-square-degree area is one-tenth that of the largest constellation, Hydra.

If you’re not sure of Triangulum’s location in the night sky, refer to the StarDome map in the center of this magazine. From mid-northern latitudes, Triangulum appears high in the December evening sky between Aries and Andromeda.

Punctuated by three stars arranged in the form of a long, narrow triangle, this constellation is aptly named. It is made up of Alpha (α) at magnitude 3.4, Beta (β) at magnitude 3.0, and Gamma (γ), which shines at magnitude 4.0. Gamma is attended by the 5th-magnitude stars Delta (δ) and 7 Trianguli. This optical triplet can be glimpsed with the naked eye under a dark sky, and it is an eye-catching sight through 7x binoculars or finder scopes.

Triangulumconstellation

Triangulum is one of the smallest constellations in the night sky. But despite its modest size, it affords informed observers many rewarding sights.

Astronomy: Roen Kelly
Some 15° east of Delta is another triangle formed by the 5th-magnitude stars 14 and 15 Trianguli and 6th-magnitude HD 15755 (shown in orange). Their spectral classes are K5, M4, and G5, respectively, so you’ll want to compare their colors through binoculars or a telescope. 15 Trianguli is a double star with a wide separation of 142". Its companion is a magnitude 6.8 A-type star, producing a striking color contrast.

Slightly east and 0.5° south of 15 Trianguli is the long-period variable R Trianguli. Over an average of nine months, this pulsating red giant’s magnitude ranges from a maximum of 5.5 to a minimum of 12.5 and back. According to “Bulletin #81” of the American Association of Variable Star Observers (AAVSO), R Trianguli is currently brightening to an early February maximum.

If you’ve never watched a star undergo a dramatic change in brightness, give R Trianguli a look-see once a week. You can create your own chart showing R Trianguli and the magnitudes of nearby comparison stars by logging on to the AAVSO website (aavso.org), or you can email me for a chart that I’ve put together.

Iota (ι) Trianguli — also known by the Flamsteed designation 6 Trianguli and the Struve double star designation Struve 227 (STF 227 or Σ227) — is a neat double star whose magnitude 5.3 and 6.7 components are separated by 3.7". One of the 110 entries on my Double Star Marathon list, it’s rapidly disappearing in the west during the March/April time slot when the Marathon is being conducted. Catch it now while it’s more conveniently placed. I recommend a magnification of at least 75x for a clean split.

While Iota is still in the eyepiece field, look about a half-degree eastward. You should spot a stellar pair that only a seasoned double star observer can see. This is Struve 232 (STF 232 or Σ232), a near-twin system (magnitudes 7.8 and 7.9) with a 6.5" separation. How unfortunate that hundreds of eye-pleasing pairs like this go unobserved because of their relative faintness. A bright showpiece double like Albireo (Beta Cygni) has the in-the-face visual impact of a snowcapped mountain peak; STF 232 possesses the delicate beauty of a single snowflake.

Triangulum’s key center of attraction is the Pinwheel Galaxy (M33). Notorious for its elusiveness, M33 spreads the light of a 6th-magnitude star over an oval-shaped area that exceeds that of a gibbous Moon. Surprisingly, M33 is faintly visible with the unaided eye and relatively easy to spot through binoculars, provided you view it from an area free of light pollution and atmospheric haze. The problem occurs if you try to view M33 with a telescope and high-power eyepiece. Instead, work with a telescope and eyepiece combination that produces a field of view 2° or more across. My best view of M33 came with a 4-inch rich-field scope and magnification of 30x.

Does my penchant for small constellations mean that I avoid the large ones? Hardly! In a few months, I’ll take you to Hydra to demonstrate how to break down an expansive constellation the way an angler dissects a large body of water.

Questions, comments, or suggestions? Email me at gchaple@hotmail.com. Next month: It’s a bird! It’s a plane! It’s Super Moon! Clear skies!

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