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Thread: Object of the Week March 12th, 2017 - NGC 4038 and 4039 / Arp 244

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    Member Howard B's Avatar
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    Object of the Week March 12th, 2017 - NGC 4038 and 4039 / Arp 244

    Antennae_galaxies_xl.jpg
    (By NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration)

    NGC 40238 and NGC 4039

    Corvus

    RA: 12 hours, 01 minutes, 53 seconds

    Dec: -18 degrees 52 minutes, 10 seconds

    Magnitude: 11.0

    Interacting galaxies


    NGC 4038 and 4039 are better known as the Antennae Galaxies and are often described as looking like a shrimp. that's certainly how it looked to me the first time I saw it in 1993 for the first time through my them brand new 20 inch scope. I have fifteen additional observations of these two galaxies since then in my notes, but there are two that stand out from the rest. More on those in a moment.

    William Herschel discovered and logged them as a single object (as a planetary nebula!) in 1785, but his son John saw them as two objects in 1833 and they've had their own catalog designations ever since. Located relatively nearby - about 45 million lights away - they're rather low for those of us in the northern hemisphere so an exceptionally good night is needed for a memorable observation.

    Simulations have suggested that about 1.2 billion years ago 4038 started out as a barred spiral and 4039, which was the larger of the two, was a spiral galaxy. Around 900 million years ago they started interacting and 600 million years ago passed through each other. The long streamer of stars that give the Antennae it's name started forming about 300 million years ago.

    Back to my two most memorable observations. Both were made with huge telescopes so they're not representative of what can be seen in more normal size amateur instruments. That's why they're so memorable!

    The first was from April 2010 with the 90 inch Bok telescope on Kitt Peak. Using 502x the main mass of 4038/4039 was full of intricate detail but I didn't see the tidal tails until my second look. Delicate, curved low-contrast streamers sailed away in opposite directions, and were best seen when I panned the scope away from the bright central area of 4038/4039. My original sketch was made of just the central area, but then I added the streamers which were partially embedded in my notes! The sketch below is a reconstruction of what I saw, minus my handwriting. 21.62 SQM.

    By the way, this is the only time I've seen so much of the tidal tails.

    NGC4038_4039_crop_small.jpg NGC4038_4039_cropinvert_3.jpg

    The second memorable observation was with Jimi's 48 inch scope in May 2016. It was during during the Texas Star Party and that particular night not only featured the best observing conditions of any night I've observed at Jimi's, but also had the largest group of observers. Here are my notes:

    "Just a quick peek because there's a big crowd here tonight, but WOW! HII knots everywhere, the beginnings of the tidal tails - bang. And then Jimi put in the NPB filter and then bang again - all the HII knots lit up and the effect was like looking at city lights from a a plane on a foggy night - silly good, indescribably awesome! Sheesh, I need to get me a scope this big...488x, 21.80 SQM."

    Jimi was the one who came up with the city lights through a fog analogy, and it was perfect - that's exactly what it looked like, which I tried to capture in this sketch.

    NGC4038_4039_crop_48inch_NPBfilter.jpg

    From 45 degrees north I've only had glimpses of details like these with my own telescopes, but I'll keep giving it a go. It just seems like the tidal tails should be detectable on a great night in my 28 scope - but time will tell.

    What are your impressions of NGC 4038 and 4039?
    Last edited by Howard B; March 13th, 2017 at 08:10 PM.
    Howard
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    Member akarsh's Avatar
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    I was impressed that one could tease out the beginnings of one of the antennae, which I first noticed when observing with John T's 25" scope. I am inclined to believe (and this is where I regret not logging well) that I could reproduce this even with the 18". Of course, neither aperture has shown me the full tidal tails.

    This object is really quite the sight through Jimi's 48".
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    Slight correction Howard. It was William's son John who saw them as two separate objects (not William :-))

    Owen

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    Member Ivan Maly's Avatar
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    Actually, Sir William's original description was "...opening with a branch, or two nebulae very faintly joined. The south is smallest." It's a recurring story of discoveries broken up by subsequent observers. I am yet to see the tails. My most recent observation was ust a quick look two weeks ago: "N component itself is a ring and a tail. Good separation of the S component [dark break on E side, not just the gulf]. 12" SCT, 13 mm Ethos, SQM 21.8-9.
    Ivan
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    Member Howard B's Avatar
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    Thanks Owen, I've corrected my typo now.

    Howard
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    Perhaps one of the most impressive object in the sky when it rises high enough.

    From the middle of Germany (~50°N) and dusty and humidity places it unfortunately remain two slightly different plobs. Details are difficult to spot out and I never saw any signs of the arms.

    ---------------------

    Moving to a mountain location from southern Germany (~47°N) revealed much more detail. The brightest HII regions blurring to brighter regions, the circle of NGC 4038 becomes visible with mid size telescopes. The fun starts. Arms are invisible in my experience.

    14.5", 283x-404x, NELM 6m5+, Seeing II (48°N)
    NGC4038_NGC4039.jpg

    ---------------------

    Moving a few thousands kilometers to the south the object became extremely beautiful. I started an attempt to sketch as much as possible with the huge 28" telescope from the Gamsberg/Namibia (perhaps one of the best observing places on earth). My focus lies on the HII regions. With an EP of around 1mm the arms were only visible at their beginnings.

    28", 446x-624x, NELM 7m5+, Seeing III (23°S)
    NGC4038_NGC4039_28.jpg

    ----------------------

    Since I know the galaxy I started a few attempts to see the arms. Here are my results so far.
    16", 75x-180x, fst 7m+ (High Alps - 47°N)
    Even under perfect transparency no signs of the arms.

    20", 107x, fst 7m+ (La Palma - 29°N)
    Northern arm visible with averted vision without knowledge of the correct position; visible as a 5' long, slightly bent nebula directly NW of a faint star chain; southern arm much more difficult and not easily visible without a detailed chart; only suspected, very faint

    24", 185x, fst 7m+ (Hakos - 23°S)
    Under Namibian sky easier than expected; sensitive on correct EP, best EP around 3mm; fainter star chains also complicated visibility; NE arm brighter and visible as a 5' long filament, slightly bent; SW arm starts brighter at the beginning, than become fainter, following again with a brighter part; SW arm longer and around 12' long; both arms wider visible

    48", 375x, fst 7m+ (Fort Davis - 31°N)
    Even with low EP (3,3mm) but big aperture immediately visible as faint but good to follow thin arms; impressive view
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    We took a look at NGC 4038-39 with tha same 24" as Uwe did at Hakos. We saw the full extent of the arms as well.

    I also tried it with 16" from Hakos in the hope of drawing it. But I could only see the very start of the southern arm (that short brighter section). The bright stars and little star chains sitting on / next to the arms are pretty much in the way.
    Peter Kiss
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    Member RolandosCY's Avatar
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    Here is my contribution from a few years ago...

    http://www.deepskyforum.com/showthre...highlight=4038
    The Darker the Better!
    -------------------------
    18" f4.5 Obsession Classic #1934
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    Televue Naglers and Ethos

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    Member RolandosCY's Avatar
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    And an observation with a 120mm refractor from last night...

    Ant1a.jpg
    The Darker the Better!
    -------------------------
    18" f4.5 Obsession Classic #1934
    10" f5 Skyatcher Dob
    152mm f5.9 Teleskop Service
    Takahashi FS128
    SkyWatcher 120 f5
    Takahashi FS102
    Takahashi FSQ106N
    SkyWatcher ED80 Pro
    SkyWatcher ED72 Evostar
    Televue Naglers and Ethos

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    Member akarsh's Avatar
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    Quote Originally Posted by akarsh View Post
    I was impressed that one could tease out the beginnings of one of the antennae, which I first noticed when observing with John T's 25" scope. I am inclined to believe (and this is where I regret not logging well) that I could reproduce this even with the 18". Of course, neither aperture has shown me the full tidal tails.

    This object is really quite the sight through Jimi's 48".
    After noting the glaring absence in my logbooks of an observation of this pair through my 18", I made sure to observe it this year: thrice. The first time, I really didn't pick up much. I was at Lake Sonoma, a Bortle 4-ish site frequented by Steve Gottlieb amongst others, with plenty of light pollution to the south. The second time, I was at a much darker site with excellent (Bortle 2-esque) southern skies, but the transparency was so-so. At high power, I was able to pick up the several knots of starburst that dot the outline of NGC 4038, and a prominent brightening in the body of NGC 4039. I also noted that the brightness of NGC 4038 has an asymmetric "hole" in it, so the star-forming regions and the nucleus form a sort of ring of light. Of course, this is a piece of cake to see in Jimi's scope where Howard Banich likened it to flying over a city at night and seeing the lights, but it was a joy to ferret this out in an 18" (it is not too difficult).

    Third time is the charm. I did see the beginning of the tidal plume that I mention in the above observation. I was at the "Hovatter Road Antenna Site" in Arizona, which I rate as Bortle 3, but the transparency must have been good and there weren't any light domes in the southern direction. Plus, it rises a tad higher at the lower latitude. The plume was barely, but reproducibly visible just off the edge of NGC 4039. This is the tidal tail of NGC 4038. I also sensed that there seemed to be a slight condensation within the plume, separated slightly from the bodies of NGC 4038 and NGC 4039 by a less brighter region.

    Clear Skies
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