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Image of the day 03/07/2017

    M94 Sp`iral Galaxy & The Outer Ring, 


            Lluis Romero Ventura

    M94 Sp`iral Galaxy & The Outer Ring


    Messier 94 (also known as NGC 4736) is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier two days later. Although some references describe M94 as a barred spiral galaxy, the "bar" structure appears to be more oval-shaped. The galaxy has two ring structures

    M94 contains both an inner ring with a diameter of 70 arcseconds and an outer ring with a diameter of 600 arcseconds. These rings appear to form at resonance locations within the disk of the galaxy. The inner ring is the site of strong star formation activity and is sometimes referred to as a starburst ring. This star formation is fueled by gas that is dynamically driven into the ring by the inner oval-shaped bar-like structure.

    A 2009 study conducted by an international team of astrophysicists revealed that the outer ring of M94 is not a closed stellar ring, as historically attributed in the literature, but a complex structure of spiral arms when viewed in mid-IR and UV. The study found that the outer disk of this galaxy is active. It contains approximately 23% of the galaxy's total stellar mass and contributes about 10% of the galaxy's new stars. In fact, the star formation rate of the outer disk is approximately two times greater than the inner disk because it is more efficient per unit of stellar mass.

    There are several possible external events that could have led to the origin of M94's outer disk including the accretion of a satellite galaxy or the gravitational interaction with a nearby star system. However, further research found problems with each of these scenarios. Therefore, the report concludes that the inner disk of M94 is an oval distortion which led to the creation of this galaxy's peripheral disk.

    The estimated average distance to M94 is estimated of 16.0 ± 1.3 Mly (4.9 ± 0.4 Mpc). In total the galaxy spans 11.2 x 9.2 arc minutes of apparent sky, which corresponds to a spatial diameter of 50,000 light-years. It's estimated to contain about 40 billion stars. The galaxy is best seen from the Northern Hemisphere during the months of March, April or May.

    M94 is one of the brightest galaxies within the M94 Group, a group of galaxies that contains between 16 and 24 galaxies. This group is one of many that lies within the Virgo Supercluster (i.e. the Local Supercluster). Although a large number of galaxies may be associated with M94, only a few galaxies near M94 appear to form a gravitationally bound system. Most of the other nearby galaxies appears to be moving with the expansion of the universe.

    M94 is a nice spiral galaxy located in the constellation of Canes Venatici. It's also known as the Cats Eye Galaxy or the Crocs Eye Galaxy due to its stunning eye-like resemblance. With an apparent magnitude of +8.5, it's a difficult binocular object requiring dark skies and good transparency; at best appearing as only a small faint hazy patch of light.

    About this Image:

    Location: Àger-Lleida-Spain
    Dates: 18-19-23 December 2016
    Average SQM: 21.4-21.6
    Telescope: GSO RC14” Truss f8
    Camera: Moravian G3-11000 classe 2
    Focuser: Feather Touch 3” Kit boss II
    Flattener: TSFlattener 2.5”
    Filters: Astrodon LRGB Gen2 I-Series True-Balance
    L:39x900 sec bin1
    L:2x1800 sec bin1
    R:G:B: 19:22:28 x 600 sec bin1 R:G:B: 24:19:18 x 900 sec bin1
    R:G:B:4:4:4: x 1800 sec bin1
    Total Exposure: 36.6 hours
    Processing: Pixinsight & Photoshop CC 2017



    Lluis Romero Ventura
    License: None (All rights reserved)


    M94 Sp`iral Galaxy & The Outer Ring, 


            Lluis Romero Ventura