How to find NGC 1981, M43 and M78 this weekend, January 17-19, 2014.
Friday, January 17 - Tonight let's return to Orion's sword to have a look for something you might have missed. Starting with M42 and M43, be sure to log these two Messier catalog studies for your binocular or small telescope records, but have a much closer look about one degree north.
NGC 1981 (Right Ascension: 5:35.2 - Declination: -04:26) is a 4th magnitude open cluster that looks like a stellar member of the Orion group to the unaided eye. In small binoculars, it is easily resolved into around a dozen members with its brightest star weighing in at around magnitude 6. In the small telescope, as many as twenty individual members are resolved in chains and small groups. The region of NGC 1981 has been studied for rotational movement in the Orion arm of our galaxy and it was found that the stars in this cluster are actually rotating around our galactic center faster than the stars in the Perseus arm.
Well suited to even urban skies, NGC 1981 is also an Astronomical League Binocular Deep Sky object that you will very much enjoy. For larger telescopes looking for a real challenge, double star Struve 750 is part of this entertaining and easy galactic cluster!
Saturday, January 18 - Tonight our study region is to the northeast of the Great Orion Nebula (M42) and has a designation of its own - M43 (Right Ascension: 5:35.6 - Declination: -05:16). Discovered by De Mairan in the latter half of the 18th century, this emission nebula appears to be separate from M42, but the division known as "the Fish Mouth" is actually caused by dark gas and dust within the nebula itself. At the heart of it is 7th magnitude "Bond's Star" - and wouldn't 007 be proud? This unusually bright OB star is creating a matter-bound Stromgren sphere!
Translated loosely, this star is actually ionizing the gas near it, making an orb-shaped area of glowing hydrogen gas. Its size is governed by the density of both the gas and dust that surround Bond's Star. This "exciting" star of our show is more properly known as Nu Orionis and near it resides in a dense concentration of neutral material known as the "Orion Ridge." It is this combination of dust - mixed with gases - that make for a well balanced area of star formation.
And besides... It's just cool!
Sunday, January 19 - Johann Bode was born today in 1747. He was the publicizer of the Titus-Bode law, a nearly geometric progression of the distances of the planets from the Sun. Also born today, but in 1851, was Jacobus Kapteyn. Kapteyn studied the distribution and motion of half a million stars and created the first modern model of the size and structure of the Milky Way Galaxy.
With plenty of dark sky early tonight, let's head around a fingerwidth northeast of Zeta Orionis and right on the celestial equator for a delightful bright nebula known as M78 (Right Ascension: 5 : 46.7 - Declination: +00 : 03). This is both a binocular and small telescope Messier challenge object.
Often overlooked in favor of the Great Orion Nebula, this 8th magnitude diffuse area is easily captured under dark skies. Discovered by Pierre Mechain in 1789, M78 is part of the vast complex of nebulae and star birth that comprise the Orion region. Fueled by twin 10th magnitude stars, the nebula almost appears to binoculars to resemble a "double comet." Upon close scrutiny with a telescope, observers will note two lobes separated by a dark band of dust. Each lobe bears its own designation - NGC 2067 to the north and NGC 2064 to the south.
While studying, you will notice the entire area is surrounded by a region of absorption, making the borders appear almost starless. Filled with T Tauri-type stars and residing 1,600 light-years away, this reflection nebula is a cloud of interstellar dust which reflects the light of these young stars, the brightest of which is HD 38563A. In 1919, Vesto Slipher was the first to discover its reflective nature. As of 1999, seventeen Herbig-Haro objects are also associated with M78, and are believed to be jets of matter being expelled from newly forming stars.
Although it's not the weekend and the Moon will greatly interfere, if you're up before dawn on the morning of January 20th, take a few minutes to watch the skies for the peak of the Coma Berenicid meteor shower. Although the activity for this one is fairly weak, with an average fall rate of about seven per hour, it still warrants study.
So what makes this particular shower of interest? Noted first in 1959, the stream was eventually tied in 1973 to another minor shower in the same orbit known as the December Leo Minorids. As we know, meteoroid streams are traditionally tied to the orbit of a comet, and in this case the comet was unconfirmed! Observed in 1912 by B. Lowe, an Australian amateur astronomer, the comet was officially designated as 1913I and was only seen four times before losing it to sunrise.
Using Lowe's observations, independent researchers computed the comet's orbit and it was basically forgotten about until 1954. At that time, Fred Whipple was studying meteoroid orbits and made the association between his photographic studies and the enigmatic comet Lowe. By continuing to observe the annual shower, it was determined that the orbital period of the comet was about 75 years, but the two major streams occurred about 27 and 157 years apart. Thanks to the uneven dispersion of material, it may be another decade before we see some real activity from this shower, but even one meteor can make your day!
And if you want to make your "night" an early one, why not trying looking for another odd meteor shower? The night of January 20th will also be the peak of the Delta Arietids! These unusual meteors also bear a resemblance to last week's Geminids, for the source of the stream appears to be a sun-grazing asteroid named Icarus. The hourly fall rate will be about 12 fast and bright "shooting stars." Be sure to watch early as the constellation of Aries will be in the best position for only a few hours after dark.
Until next week. Keep reaching for the stars!
Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She's received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status.