4 Attachment(s)
Object of the Week March 12th, 2017 - NGC 4038 and 4039 / Arp 244
Attachment 2497
(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.
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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.
Attachment 2496
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?
