It’s that time again! We have a new month and some new targets for you to pursue, whether you be a visual observer, sketcher or imager. The sky has shifted a little more of course bringing some new stuff to center stage, but don’t forget the March objects either if you have not visited them. They too are still accessible. So let’s take a closer look at what I have selected for you this month.
Northern Celestial Hemisphere:
Messier 65 / NGC 3623 (Leo, barred spiral galaxy, mag=9.3, size=9.8’x2.9’, SBr=12.8):
Messier 66 / NGC 3627 (Leo, barred spiral galaxy, mag=8.9, size=9.1’x4.2’, SBr=12.7):
NGC 3628 (Leo, barred spiral galaxy, mag=9.5, size=14.8’x3.0’, SBr=13.4):
Representing the northern celestial hemisphere this month I have selected the Leo Triplet. This trio of galaxies is a spring staple just below the lion’s hindquarters. The two main components, Messier 65 and 66 were discovered by Charles Messier on 01 March 1780, with the third, NGC 3628, discovered by William Herschel on 08 April 1784.
The galaxies form an isosceles triangle tipped slightly NNE, with NGC 3628 at the apex about 36’ north of M66 and about the same distance NNE of M65. The two Messier galaxies lie closer together at the base of the triangular grouping, separated by about 20’. At a distance from us of about 35 MLY, the trio is an actual interacting group. Collectively the group is found in Dr. Halton Arp’s Atlas of Peculiar Galaxies under the category “Groups of galaxies” as Arp 317. M66 displays signs of distortion due to interaction in the past, most likely with NGC 3628, and itself is found in the Arp atlas as Arp 16 in the category titled “Galaxies with detached segments.”
The appearance of the two parallel ovals of M65 and M66 close together with the dimmer thin oval of NGC 3628 oriented perpendicular to the Messier galaxies to its south is an intriguing view in the same field. Look for brighter cores within the Messier duo, and possibly an uneven mottled appearance in M66. The larger NGC 3628 may also appear uneven along its major axis due to the dark lane bisecting its edge on disk. So take your time to both locate and study this fine trio of galaxies. They lie in a rich area of the sky for galaxies and are certainly highlights of the early spring sky.
Southern Celestial Hemisphere:
NGC 3372 (Carina, emission nebula, mag=3.0, size=2.0°):
Let us travel to the large southern constellation, Carina the keel, which was formerly part of the gigantic constellation Argo Navis. Here we will pursue what I believe is the finest emission nebula in the sky. That is not said to negate the prominence and beauty of Messier 42 in the least. But the first time I laid eyes on this behemoth I was simply astounded. Discovered telescopically by Nicolas-Louis de Lacaille in 1751, it was also observed numerous times by James Dunlop. John Herschel had this to say about the nebula: "It is not easy for language to convey a full impression of the beauty and sublimity of the spectacle which this nebula offers, as it enters the field of the telescope fixed in R. A., by the diurnal motion, ushered in as it is by so glorious and innumerable a procession of stars, to which it forms a sort of climax, and in a part of the heavens otherwise full of interest."
Known famously as the Eta Carinae Nebula, even from about a Bortle 5 suburban location just south of the equator I found it an easy naked eye object and very bright and curious in 10x50 binoculars. With a scope of most any aperture it turns into a true showpiece of various clumps and knots of nebulosity, permeated by dark lanes in various directions. If you have a narrow-band nebula filter, give it a try. This is truly is a visual wonder.
Embedded within its huge glowing field are various open clusters such as Trumpler 14, 15 and 16 as well as Bochum 10. Of course there is also the namesake star Eta Carinae, which is expected to go supernova at some point soon, in astronomical terms that is. There are two lobes emanating from this star, known as the Homunculus Nebula. These lobes are the result of an outburst from Eta Carinae in the late 1840s into the 1850s which saw the star brighten from about magnitude 1.5 to -1.0. This even was chronicled by John Herschel. Eta Carinae now shines at about magnitude 6.4 biding its time. Also within the nebula complex is a prominent dark nebula within the complex, named the “Keyhole Nebula.”
This object is a true gem of the southern sky and is a fine target for visual (and sketchers) observers and imagers alike. So why not turn your scope its way to enjoy its bright silent beauty, with its undertone of violent activity from Eta Carinae.
NGC 3115 (Sextans, lenticular galaxy, mag=8.9, size=7.2’x2.5’, SBr=11.9):
We next head to the heavenly sextant. This constellation straddles the celestial equator, but our target lies almost 8° to its south. Sometimes called the spindle galaxy it is bright even from my typically Bortle 5 backyard. It appears as a thin sliver of bright diffuse light, with a core that is brighter still. Its central bulge tapers out to thin tips at both ends.
Discovered by William Herschel in 1787 he described it as bright, large and extended. This lenticular is the brightest galaxy in Sextans, a constellation frequently overlooked by observers since it is not bright and contains no Messier objects. With its brightest star (Alpha) shining meekly at magnitude 4.5 the constellation lies quietly between Leo and Hydra.
NGC 3132 (Vela, planetary nebula, mag=9.2, size=1.5’x1.4’, SBr=9.7):
We finish up this month in another former portion of the old constellation Argo Navis. Vela the sails is home to this excellent planetary nebula informally known as the Eight Burst Nebula or the Southern Ring Nebula. Discovered on 02 Mar 1835 by John Herschel, he recorded it as a "planetary nebula, very large, very bright, elliptic.”
I recommend using at least a narrow-band nebula filter to give it more visual contrast. Even better is an O-III line filter for bringing out detail with the nebula’s disk. I found while observing it with a 5-inch refractor that without a filter the magnitude 10.0 central star tended to overwhelm the envelope of the planetary, so using a filter will tame that star allowing one to see more of the nebular structure. It is a fine object for imagers who wish to experiment with trying to pull out deeper details. So give it a try and see what you can do with this nice planetary.
There you have it for this month. I hope you enjoy the pursuit and the challenges that I have presented to you, whether you live north, south or somewhere between. The sky is a treasure trove of wonderfully beautiful objects of many types, and they are just waiting for those with the desire and patience to find them. Good luck friends!
Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob
ES AR127 f/6.5 & ED80 f/6 on Twilight-II || Apertura 6" f/5 Newtonian on Twilight-I
TV Ethos 100° 21mm, 13mm || ES 82° 24mm, 18mm || Vixen LVW 65° 22mm
Pentax XW 70° 10mm, 7mm, 5mm || barlows
DGM NPB Filter || Orion Ultra Block, O-III and Sky Glow Filters || Baader HaB Filter
Primary Field Atlases: Interstellarum and Uranometria All-Sky Edition
"Astronomers, we look into the past to see our future." (me)
"What we know is a drop, what we don't know is an ocean." (Sir Isaac Newton)
"The eternal silence of these infinite spaces frightens me...." (Blaise Pascal)
"No good deed goes unpunished. (various)