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NGC 7027
Planetary Nebula
NGC 7027, PNG 084.9-03.4, PK 084-03.1, ARO 40
Integrated Visual Magnitude: 10.4
Apparent Diameter: 14"
Distance: 2600 ly
Actual Diameter: 11,000 AU

Minimum requirements to view: 4-inch, country skies


NGC 7027 is a small, relatively bright planetary nebula that is a delight in just about any telescope. It has been a favorite planetary of mine since my first observation with my 6-inch Newtonian in 1977. This is also a very interesting planetary from a science standpoint because it is actually a rare class of object called a proto-planetary nebula.

In a 6-inch at 50x NGC 7027 looks like a 9th magnitude star. At higher magnifications it has a slight oval shape. Experienced observers may be able to tell that there is something "funny" about it. For the best view use as much magnification as your telescope and sky conditions will permit. At 270x it is clearly oval in shape. I noted that it appeared brighter at the northwest end.

More recently, and armed with my 18-inch f/4.5 Dob and an OIII filter, I was amazed at the sight that greeted me at 430x. Fantastic! All my previous logs describe an elongated, egg shape. But this night it appeared as a green rectangle with soft edges. The northwest quarter appeared brighter and within it, near the long edge, could be seen at least two tiny bright knots! Unfortunately I didn't think to look for the 16th magnitude central star. In short, it looked very much like the image at the top of the page, only with much less detail.

Time and time again I've discovered detail in planetaries with this scope that had not previously been visible--more than that, I didn't believe they were visible--in any scope! Those of you with large Dobs who haven't discovered planetaries should give some of these a try. To my mind there is no better example of the advantages of a large Dob. For best results I use high magnification (at least 400x and as much as 50x per inch or aperture or more depending on the seeing conditions and the surface brightness of the object). 


The field in a 6-inch telescope at 50x. North is down and East is right.

NGC 7027 appears to be a proto-planetary nebula; a very young object intermediate between a pulsating giant star and a true planetary nebula. The central star at the root of all this was a pulsating giant as recently as a few thousand years ago, a blink of an eye on cosmic time scales. As the star aged it swelled to many times its previous diameter, became much brighter, and began to pulsate. These pulsations drove material away from the star in concentric shells. This material is made of molecules such as hydrogen and carbon monoxide and is relatively cool. As the central star continued to evolve it became much hotter, producing ionizing ultraviolet radiation. The central star currently is as hot as 200,000K and shines some 5000 times brighter than the sun! This radiation breaks up the molecules of the surrounding gas into their constituent atoms, a process that takes only a few thousand years. The atoms then become ionized (lose one or more electrons) as they absorb the ultraviolet light. It is this final stage of a star surrounded by ionized, glowing, gas that we call a planetary nebula. The presence of molecules in the spectrum of NGC 7027 indicates that we have caught it in the short lived process of becoming a planetary; a rare proto-planetary nebula.

NGC 7027 Links:
Staring Into the Winds of Destruction
 

Millennium Star Atlas Vol III Chart 1126
Sky Atlas 2000 Chart 9
Uranometria 2000 Vol I Chart 85