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Thread: Object of the Week February 11, 2018 - NGC 2217

  1. #1
    Member deepskytraveler's Avatar
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    Object of the Week February 11, 2018 - NGC 2217

    Object of the Week February 11, 2018 - NGC 2217

    NGC 2217, MCG -5-15-10, ESO 489 42, PGC 18883
    Type: (R)SB(rs)0/a
    Classification: Lenticular, nearly face-on
    Constellation: Canis Major
    RA: 6h 21m 40.0s
    Dec: -27° 14' 3"
    Magnitude: 10.7v, 11.6B
    Mean Surface Brightness: 13.4
    Size: 4.5' x 4.2'

    Take a moment to observe and reflect on this beautiful deep image of NGC 2217 before you read further.

    ngc2217 chart-c.jpg

    NGC 2217 was discovered by John Herschel on January 20, 1835 during sweep #530. It was logged as h3041 with this description "vB; R; p s m b M; 30"; r" or "very bright, round, pretty suddenly much brighter in the middle, 30" (in size), resolvable."

    ngc 2217 dssII red band-c.jpg

    NGC 2217 is an 11th magnitude lenticular galaxy in Canis Major. In Gérard de Vaucouleurs' Atlas of Galaxy Types NGC 2217 is the poster child for galaxy type (R)SB(rs)0/a with the following description, "This face-on galaxy includes a strong bar and a very well-defined inner pseudo-ring of the wrapped arm type. The ring is formed from two arms which break from opposite ends of the bar. The inner pseudo-ring fades quickly outside the bar region. At about twice the inner pseudo-ring radius, a large, well-defined outer ring is found. This ring also appears made partly of spiral structure, and includes considerable patchiness on one side. Weak dust structures are found in the bar and inner pseudo-ring area. Recent star formation is largely confined to the outer ring. Bettoni et al. (2001) attribute an apparent counter-rotation to a warped inner disk, i.e., a projected view of a series of polar rings in this region. Jungwiert et al. (1997) also identified a secondary bar in this region. This feature is visible in the Atlas image as a small inner oval."

    In the Annals of the Deep Sky: A Survey of Galactic and Extragalactic Objects Volume 3 by Jeff Kanipe and Dennis Webb, they share the following description of NGC 2217. "Deep images show a striking face-on galaxy with an apparent outer ring and a strong central bar measuring well over an arcminute across its major axis. The spiral arms wrapping tightly around the bar form a well-defined inner pseudo-ring. The inner ring quickly fades outside the board, giving way to a kind of dusky circular gulf about40 arcseconds across. However, the outer ring appears to consist of two spirals that almost overlap to form a second pseudo-ring. The outer arms contain several H II regions, including an extended region along the NE arm."

    Long-slit spectroscopy studies on NGC 2217 by Florido et. al. (2012) confirmed the existence of a LINER-type (LINER = low-ionization nuclear emission-line regions) active galactic nucleus.

    Wow! There is a lot going with this galaxy as seen in the many deep images. Now it's your turn to give NGC 2217 a go visually. Fair warning: at declination -27° this one isn't real high for those of us in the upper-mid northern latitudes. If that means you, you'll want to find an unobstructed southern horizon. January and February are the best months of year to catch NGC 2217 as it transits at its highest altitude.

    Regardless of the aperture of your telescope, you definitely will want to crank up the magnification on NGC 2217. At the lower range of aperture, between 8" to 15", expect to see the galaxy as anything from a small amorphous faint fuzzy to an elongated halo with brightening from a nonstellar core. A pair of faint stars (12 and 13 magnitude) just off the western edge of the galaxy should be visible. These stars are embedded in the outer ring which is highly unlikely to be seen. As you move up in aperture range it should become a bit easier to tease out the fainter structure that is readily visible in the deep images. As previously mentioned don't forget to crank up your magnification!

    Give it a go and let us know!
    Last edited by deepskytraveler; February 12th, 2018 at 02:36 AM.
    Clear Skies,

    Mark Friedman
    Wheaton, IL USA
    15" f/4.5 Obsession Classic #973
    Stellarvue SV90TBV

  2. #2
    Administrator/Co-Founder Dragan's Avatar
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    Beautiful galaxy Mark! Great choice!
    Clear Dark Skies,
    Dragan Nikin
    25" f/5 Obsession #610 "Toto"
    30" f/4.5 OMI EVO
    www.darkskiesapparel.com

  3. #3
    With an LX200 10" at 185x, an observation dated from eighteen years ago !
    Southern Alps, good transparency, about nelm 6.5v, weak pollution, about SQM 21.5

    Pretty beauteful small galaxy, concentrated, seen in direct vision in a rich field.
    Little elongated, a/b ~ 1.25, D ~ 3.5'.
    The center is concentrated, almost brillant in adverted vision.
    No more details seen.

    Bertrand
    http://www.deepsky-drawings.com/dsdlang/en/

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