Messier 27 - The Dumbbell Nebula

By tammy-plotner - November 21, 2016 at 4:16 PM UTC | Stars
Dumbbell-Nebula.jpg

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the famous and easily-spotted Dumbbell Nebula. Enjoy!

Back in the 18th century, famed French astronomer Charles Messier noted the presence of several "nebulous objects" in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list would come to include 100 of the most fabulous objects in the night sky.

Known today as the

Messier Catalog

, this work has come to be viewed as one of the most important milestones in the study of Deep Space Objects. One of these is the famed Dumbbell Nebula - also known as Messier 27, the Apple Core Nebula, and NGC 6853. Because it of its brightness, it is easily viewed with binoculars and amateur telescopes, and was the first planetary Nebula to be discovered by Charles Messier.

Description:

This bright planetary nebula is located in the direction of the

Vulpecula constellation

, at a distance of about 1,360 light years from Earth. Located within the equatorial plane, this nebula is essentially a dying star that has been ejecting a shell of hot gas into space for roughly 48,000 years.

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Picture of M27 processed and combined using IRAF and MaxIm DL. Credit: Wikipedia Commons/Mohamad Abbas

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The star responsible is an extremely hot blueish subdwarf star, which emits primarily highly energetic radiation in the non-visible part of the electromagnetic spectrum. This energy is absorbed by exciting the nebula's gas, and then re-emitted by the nebula. Messier 27 particular green glow (hence the nickname "Apple Core Nebula") is due to the presence of doubly-ionized oxygen in its center, which emits green light at 5007 Angstroms.

For many years I quested to understand the distant and mysterious M27, but no one could answer my questions. I researched it, and learned that it was made up of doubly ionized oxygen. I had hoped that perhaps there was a spectral reason to what I viewed year after year – but still no answer.

Like all amateurs, I became the victim of "aperture fever" and I continued to study M27 with a 12" telescope, never realizing the answer was right there – I just hadn't powered up enough. Several years later while studying at the Observatory, I was viewing through a friend's identical 12" telescope and, as chance would have it, he was using about twice the magnification that I normally used on the "Dumbbell."

Imagine my total astonishment as I realized for the very first time that the faint central star had an even fainter companion that made it seem to wink! At smaller apertures or low power, this was not revealed. Still, the eye could "see" a movement within the nebula – the central, radiating star and its companion.

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Image from a ground-based telescope at Westview Observatory in Cridersville, OH. Credit: Wikipedia Commons/Charlemagne920

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As W.G. Mathews of the University of California put it in his study "

Dynamical Evolution of a Model Planetary Nebula"

:

R.E. Lupu of John Hopkins has also made studies of motion as well, which they published in a study titled "

Discovery of Lyman-alpha Pumped Molecular Hydrogen Emission in the Planetary Nebulae NGC 6853 and NGC 3132

". As they indicated, and found them to "have low surface brightness signatures in the visible and near infrared."

But, movement or no movement, Messier 27 is known as one of the top "polluters" of the interstellar medium. As Joseph L. Hora ( et al.) of the Harvard-Smithsonian Center for Astrophysics said in his 2008 study "

Planetary Nebulae: Exposing the Top Polluters of the ISM

":

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Messier 27 and the Summer Triangle. Credit: Wikisky

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History of Observation:

So, chances are on July 12th, 1764, when Charles Messier discovered this new and fascinating class of objects, he didn't really have a clue as to how important his observation would be. From his notes of that night, he reports:

Of course, Sir William Herschel's own curiosity would get the better of him and although he would never publish his own findings on an object previously cataloged by Messier, he did keep his own private notes. Here is an excerpt from just one of his many observations:

So where did Messier 27 get its famous moniker? From Sir John Herschel, who wrote: "A most extraordinary object; very bright; an unresolved nebula, shaped something like an hour-glass, filled into an oval outline with a much less dense nebulosity. The central mass may be compared to a vertebra or a dumb-bell. The southern head is denser than the northern. One or two stars seen in it."

It would be several years, and several more historical astronomers, before the true nature of Messier 27 would even be hinted at. At one level, they understood it to be a nebula - but it wasn't until 1864 when William Huggins came along and began to decode the mystery:

Whether or not you enjoy M27 as one of the most superb planetary nebula in the night sky (or as a science object) you will 100% agree with the words of of Burnham: "The observer who spends a few moments in quiet contemplation of this nebula will be made aware of direct contact with cosmic things; even the radiation reaching us from the celestial depths is of a type unknown on Earth…"

Locating Messier 27:

When you first begin, Messier 27 will seem like such an elusive target - but with a few simple sky "tricks", it won't be long until you'll be finding this spectacular planetary nebula under just about any sky conditions. The hardest part is simply sorting out all the stars in the area to know the right ones to aim at!

The way I found easiest to teach others was to start BIG. The cruciform patterns of the

Cygnus

and

Aquila

constellations are easy to recognize and can be seen from even urban locations. Once you've identified these two constellations, you're going smaller by locating

Lyra

and the tiny kite-shape of

Delphinus

.

Now you've circled the area and the hunt for Vulpecula the Fox begins! What's that you say? You can't distinguish Vulpecula's primary stars from the rest of the field? You're right. They don't stand out like they should, and being tempted to simply aim halfway between Albeireo (Beta Cygni) and Alpha Delphini is too much of a span to be accurate. So what are we going to do? Here's where some patience comes into play.

If you give yourself time, you'll begin to notice the stars of

Sagitta

are ever so slightly brighter than the rest of the field stars around it, and it won't be long until you pick out that arrow pattern. In your mind, measure the distance between Delta and Gamma (the 8 and Y shape on a starfinder map) and then just aim your binoculars or finderscope exactly that same distance due north of Gamma.

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The location of M27 in the constellation Vulpecula. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

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You'll find M27 every time! In average binoculars it will appear as a fuzzy, out of focus large star in a stellar field. In the finderscope, it may not appear at all... But in a telescope? Be prepared to be blown away! And here are the quick facts on the Dumbbell Nebula to help get you started:

Object Name

Messier 27

Alternative Designations

M27, NGC 6853, The Dumbbell Nebula

Object Type

Planetary Nebula

Constellation

Vulpecula

Right Ascension

19 : 59.6 (h:m)

Declination

+22 : 43 (deg:m)

Distance

1.25 (kly)

Visual Brightness

7.4 (mag)

Apparent Dimension

8.0×5.7 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here's Tammy Plotner's

Introduction to the Messier Objects

, ,

M1 – The Crab Nebula

,

M8 – The Lagoon Nebula

, and David Dickison's articles on the

2013

and

2014

Messier Marathons.

Be to sure to check out our complete

Messier Catalog

. And for more information, check out the

SEDS Messier Database

.

Sources: