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Thread: Object of the Week December 14, 2014 – Hickson 16 (Arp 318)

  1. #1
    Join Date
    Feb 2012

    Object of the Week December 14, 2014 – Hickson 16 (Arp 318)

    Hickson 16 (Arp 318)

    Galaxy Chain (8' length)
    RA: 02h 9.5m
    Dec: -10° 09'
    Magnitude: V 12.2-13.1

    NGC 833 = HCG 16B
    02h09m20.8s -10d07m59s
    Mag 12.8v

    NGC 835 = HCG 16A
    02h09m24.6s -10d08m09s
    Mag 12.2v

    NGC 838 = HCG 16C
    02h09m38.5s -10d08m48s
    Mag 13.0v

    NGC 839 = HCG 16D
    02h09m42.9s -10d11m03s
    Mag 13.1v

    For lovers of compact galaxy groups – especially galaxy chains, for owner of smaller apertures or simply for people who wants to see things without staring hours through the eyepiece to see almost nothing – Hickson 16 is the perfect starting point to have fun with.

    The group consist of 4 NGC members which are lined up in a slightly bend line of approx 8’ length in the SE part of Cetus, an area which is rare visited when Orion and the winter constellations almost rises.

    Herschel discovered all four members in 1785. He described all four together but did not mention the word “chain” which was made-up from Burbidge in 1959. Halton Arp mentioned all four NGC galaxies under the designation number 318 in the group “Groups of Galaxies” and not as “Chains of Galaxies”. He describes the group with the words “faint, diffuse streamers; peculiar galaxies”. Paul Hickson picks up also all four NGC members in his catalog in 1982.

    Physically all four named galaxies belong together at a distance of approx 160 mLj (~4000 km/s). Ribeiro et al. (1996ApJ...463L...5R) named three other galaxies which belong to the group (NGC 848, PGC 8210, PGC 984499). Beside these three there are several other nearby galaxies which has discordant redshifts (1997ApJS...110....1D)

    All in all it seems that HCG 16 is an unusually active compact group. The group was often visited and some paper spoke about the highest starburst activity in the nearby Universe.

    For the practical aspect the observability started almost with 4” aperture. With the faintest brightness around 13vmag all four members could be a catch under very good transparency. Under suburban skies an 8” telescope should show all members plus NGC 848 without problems. With bigger aperture the other members and nearby non members could be a target. The tidal tails especially the E arm of NGC 835 could be an interesting detail. Another detail is NGC 835 itself. It shows a indistinctive ring structure which was already visited by the science (2012ApJ…745…105W)

    DSSb 45'x45' (red: group members;
    blue: discordant nearby galaxies


    picture of Arp 318
    trough the 200" Palomar


    projected distribution of galaxies around each
    compact group (from 1997ApJS...110....1D)


    sketch with: 16", 277x, NELM 6m5+
    (inverted version)


    “Give it a go and let us know”
    Clear Skies, uwe

    27" f/4,2

  2. #2
    Member hajuem's Avatar
    Join Date
    Jul 2012
    Stafflangen, Germany
    Hi Uwe

    Interesting objekts!! Ihave listed for Dezember!! Perhaps together??

    CS Hajü

  3. #3
    Join Date
    Feb 2012
    Hi Hajü,

    should be an easy target for your 16" and perhaps an object for your hidden treasure list. Simply a good mood object. I also hope for some December nights but actually it doesn't look really good. But I have a "plan B"
    Clear Skies, uwe

    27" f/4,2

  4. #4
    Member akarsh's Avatar
    Join Date
    Nov 2013
    Austin, TX
    My poor logging from back in the day says nothing but "Easy, bright Hickson group made of NGCs", and that I used a 7mm Nagler / 18". It's definitely quite easy in an 18". Obviously, I couldn't see the tidal arm, although I did try for it.
    18" f/4.5 Obsession dob "Romela"
    6" SkyQuest Orion dob
    Logbook Project : KStars
    Austin Astronomical Society : Bangalore Astronomical Society

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