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Thread: Object of the Week August 21, 2016 - NGC 7027 The Green Rectangle

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    Member deepskytraveler's Avatar
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    Object of the Week August 21, 2016 - NGC 7027 The Green Rectangle

    Object of the Week August 21, 2016 - NGC 7027 The Green Rectangle

    NGC 7027, PK 084-3.1, PN G084.9-03.4, ARO 40
    Type: Planetary Nebula
    Constellation: Cygnus
    RA: 21h 07m 1.7s
    Dec: +42° 14’ 10”
    Size: 18” x 10”
    Magnitude(v): 8.5

    This week’s OOTW starts off with a quiz; the subject matter being planetary nebulae. Limit your answers to planetary nebulae in the Northern skies.

    1. In terms of visual magnitude what is the brightest planetary nebula in the Northern Hemisphere sky? NGC 7293, the Helix Nebula in Aquarius
    2. Which planetary nebula do you expect is the most frequently observed by amateurs? The Dumbbell (M27) in Vulpecula
    3. Of the 25 brightest planetary nebulae which do you expect may be the least observed by amateurs? NGC 7027 in Cygnus (Stephen James O’Meara, Deep Sky Companions: Hidden Treasures, pg. 514)
    4. Which planetary nebula has inspired more papers in professional journals than any other object of its kind? NGC 7027 (Steven J. Hynes, Planetary Nebula, pg. 101)
    5. What is this week’s Object of the Week? NGC 7027


    NGC 7027 was discovered by French astronomer Edouard Jean-Marie Stephan using the 31-inch reflector at Marseille Observatory in 1878. In case Edouard’s name doesn’t ring a bell - a year earlier in 1877 he had discovered a visual grouping of galaxies in Pegasus; today this grouping is commonly known as Stephan’s Quintet (ARP 319, NGC 7317-7320). A year after Stephan’s discovery of NGC 7027 it was independently discovered by the Reverend Thomas W. Webb. Both Stephan and Webb called this object a “planetary nebula” following the classification established by William Herschel from his discovery of NGC 1514. According to Herschel NGC 1514 appeared to be a single star “surrounded with a faintly luminous atmosphere.” However, it was also similar in size and shared the same coloration of the recently discovered planet Uranus. Thinking these objects were the same, Herschel creatively labeled NGC 1514 a “planetary nebula”. Five hundred years later we still call them planetary nebula.

    n7027ngcicproject.jpg
    Courtesy The NGC/IC Project

    Stephan O’Meara in his book Deep Sky Companions: Hidden Treasures presents a case that NGC 7027 “is one of the brightest, smallest, most unusual, and arguably the most fascinating planetary nebula in the sky. It is, hands down, the most extensively studied – both observationally and theoretically.” Let’s briefly examine the evidence.

    One of the brightest – With a visual magnitude of 8.5 NGC 7027 is in the top 25 of brightest (visual magnitude) planetary nebulae (in the Northern skies).

    One of the smallest – We’re talking true size here, not apparent size. Most planetary nebulae extend about 1 light year in true physical extent, NGC 7027 measures only 0.2 x 0.1 light years.

    Most unusual and most fascinating – The intensity of NGC 7027’s radio emissions is so great that astronomers determined it to be one of the densest planetary nebula known, which implies it is one of the youngest known – less than a thousand years old – barely a newborn in the scale of cosmological time. Not only is this planetary a strong radio source, but it is also a strong emitter of infrared radiation, an indicator that is contains a lot of dust. The spectrum of NGC 7027 contains rich atomic lines and complex molecules, including some complex organic compounds.

    NGC 7027’s central star is faint at 16.3 magnitude; it was not visually seen until it was first imaged with the Hubble Space Telescope in 1997. The HST data revealed that the central star has a temperature of 200,000°C (360,000°F), making it one of the hottest stars known. The star sits in the center of a ring of gas and dust that is highly ionized by the radiation from the hot star. This ring is surrounded by a fluorescent pink pillow of molecular hydrogen.

    opo9811d.jpg
    This composite color image of NGC 7027 is among the first data of a planetary nebula taken with NICMOS.
    This picture is actually composed of three separate images taken at different wavelengths.
    The red color represents cool molecular hydrogen gas, the most abundant gas in the universe.
    Credit: William B. Latter (SIRTF Science Center/Caltech) and NASA/ESA



    NGC 7027 has a variety of nicknames. Stephen O’Meara tagged it with the names: Pink Pillow Nebula and Sugar Pops Nebula; both derived from the color images taken through different Hubble Space Telescope cameras. The nebula has two other popular names, the Green Rectangle and the Magic Carpet. The name, Green Rectangle, was given by Kent Wallace from his observations through a 20-inch telescope at high powers.

    Visually NGC 7027 is detectable in 10x50 binoculars - it looks like a star. In moderate aperture scopes (up to 10 inches) at low to medium powers the nebula appears somewhat elliptical in shape and diffused throughout. One end of the object appears a bit brighter than the rest of the nebula. I am unable to detect any color; however, many observers report a range of blue-green coloration. Moving up to larger apertures and higher powers really makes a difference on NGC 7027. In a 15” scope the shape of nebula appears more like a rectangle with diffused, loosely defined edges. The bright spot toward one end is well pronounced.

    NGC7027 by Massimo Zecchin .jpg
    Sketch of NGC 7027 as observed through a 120mm refractor at 250X
    (c) Massimo Zecchin


    DSF member Akarsh Simha posted an observing report of NGC 7027 from 24/25 October 2014 using Jimi’s 48-inch scope. Akarsh writes: “The planetary nebula looked roughly like the smiley face =). Two horizontal fragments were separated by a dark space, and separated by a vertical dark lane with a vertical fragment that curved slightly concave towards the horizontal fragments. The top horizontal fragment had a bright condensation, like a knot, on the side towards the curved vertical fragment. The knot, although initially stellar in appearance, had a gradually decaying intensity profile. The bottom horizontal fragment was not as long as the top one.”

    Another DSF member, Victor van Wulfen, posted a highly detailed observation of NGC 7027 from his 12-inch SCT that can be found here. Other members have contributed their own observations, including some excellent sketches. I highly recommend taking the time to go through this other NGC 7027 thread in its entirety.

    As we transition from late Summer into early Autumn here in the Northern Hemisphere the placement of Cygnus and NGC 7027 doesn’t get any better any other time. So grab your scope and….

    "Give it a go and let us know!”
    Last edited by deepskytraveler; August 22nd, 2016 at 03:43 AM.
    Clear Skies,

    Mark Friedman
    Wheaton, IL USA

  2. #2
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    In my Binos it's a tiny green star.

    In a large scope I've seen it as a bright glow divided into three unequal parts by dust lanes.
    18" f/3.5 New Moon Dob,
    12.5? New Moon Dob
    8? f/5.5 Parallax Newt
    82mm Kowa Binos
    Richmond Va

  3. #3
    Member Sue French's Avatar
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    This is with a 15-inch Obsession at 247x.NGC 7027comp.jpg

  4. #4
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    Very nice choice Mark.

    To be complete I will add my two sketches of the object.

    16", 450x, UHC, NELM 6m5+, Seeing II
    NGC7027.jpg




    27", 977x, no filter, NELM 7m0+, Seeing II
    NGC7027_27.jpg
    Clear Skies, uwe
    http://www.deepsky-visuell.de
    Germany

    27" f/4,2

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