Hidden Treasures 30, 31, & 32

NGC 1981, Collindcr 72, & NGC 1977

• ; iV-HT 30

HT 31 j •


South O Stephen O'M.,

NGC 1977, M78, Barnard's Loop, and the numerous bright and dark nebulae near Zeta Orionis (see Hidden Treasure 34). The cloud, which formed when a density wave triggered the collapse of gas and dust into hot young stars, measures several hundred light-years across. Collectively, this swath of new suns is known as the Orion OB1 Association. The association is further divided into subgroups: OB1a, which includes the stars in and around Orion's Belt;OB1b, which covers the region northwest of Orion's Belt;and OB1c, which contains Orion's Sword. The very youngest of these stars, those found in M42-M43 are sometimes considered a separate subgroup, OB 1d. The stars involved in NGC 1977, then belong to the Orion OB1c group of this spectacular realm of telescopic riches.

NGC 1977 is fainter than the Orion Nebula and not as extensive. Still, it is a marvelous sight. A close pair of 5th-magnitude stars (42 and 45 Ori) reside in the nebula's brightest section. Johann Bayer (1572-1625) saw only one star here with the naked eye, which he labeled "c" on his famous Ura-nometria (1603) atlas. Galileo and other telescopic observers resolved the star into two components (c1 and c2), and John Flam-steed (1646-1719) relabeled them 42 and 45 Ori, respectively. This explains the curious start to Herschel's discovery description of the object, "The 1st and 2nd c Orionis, and the stars about them," and the 1888 NGC description," Remarkable,^ 42 Orionis and nebula (V30)."

Since 42 and 45 Ori are aligned with the nebula's major axis, it is difficult to differentiate between true nebulosity and the "fuzzy" nature of two dim stars seen close together with the unaided eye. Then again, I have seen several reports of observers seeing the nebula with the unaided eye, with some saying it is "easy." No matter, the nebula is easy to detect in 7 x 50 binoculars; through my antique telescope, the two 5th-magnitude stars look like car headlights emerging from a fog.

Through the 4-inch at 23 x, which gives a nearly 3° field of view, NGC 1977 is a glorious network of nebulous fabric. It looks elegant, like wrinkled silk. At first the glow has a roughly uniform texture, but that illusion breaks down after spending any time with it. Discerning eyes should see NGC 1977 as three distinct, and near parallel, banks of bright nebulosity, sliced and separated by dark streams of obscuring matter. Pockets of glowing gas, like white foamed reefs, surround a half dozen or so

Was this article helpful?

0 0

Post a comment