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Gyulbudaghian's Nebula

For 10-inch or larger telescopes under dark skies

Gyulbudaghian's Nebula is a little-known variable reflection nebula, similar to Hubble's variable nebula.  This nebula changes brightness and shape over many months or years.  In years past it has been a challenge for an 18-inch scope under dark skies, but this month Gyulbudaghian's Nebula is much brighter, making this the perfect time to try to detect it in smaller instruments.

Armen Gyulbudaghian is an Armenian astronomer at Byurakan Observatory.  He discovered this nebula in 1977,  apparently during a survey for new Herbig-Haro objects.  The object as a whole is known as HH 215; the reflection nebula is officially cataloged as GM 1-29 (Magakyan -- the "M" -- was co-author on the discovery paper). 

At the heart of the Herbig-Haro object lies the variable Herbig AbBe pre-main sequence star PV Cep.  This is a newly formed star that is surrounded by a rotating disk of material.  At right angles to this disk are two jets of material, streaming away from the star at high speeds.  We see the effects of one of these jets on the north side of PV Cep as the stream of material meets the surrounding gas in the interstellar medium.  The jet to the south is obscured by a dark nebula (producing an absorption of over 3 magnitudes).  It can be seen faintly on the red POSS 2 image (right) as a string of tiny knots.  The northern jet appears on long-exposure photographs as a long chain of knots some 90" long.  This chain was more visible in the 1950's than it is today.  

Today, a bright fan-shaped reflection nebula appears immediately to the northeast of the star.  This reflection nebula appears to be the outer edges of a hollow shell that has been carved out of the interstellar medium surrounding the gas stream.  The dust on the outskirts of the shell is illuminated by the star.  As the light passes through the dusty cloud it is absorbed and scattered.  The blue light is most easily scattered so the nebula appears blue.  As the star varies in brightness so does the nebula.

Stars form together in groups, so there are at least 10 other HH objects in the vicinity, but none are as visible as HH 215.  The distance to the Herbig-Haro object has been estimated to be about 1600 light years.  At that distance the reflection nebula is about 0.2 ly in diameter.  The distance to the end of the southern jet is about 0.7 ly.

I have made an annual visit to Gyulbudaghian's Nebula with my 18-inch every fall for the last several years.  In 2001 the nebula was very difficult: it wasn't visible at all at 97x and I was able to detect it at 170x only with great effort and averted vision.

In October of 2002 it appeared much brighter.  At 94x a definite irregularly-shaped fuzz-knot was seen with averted vision.  At 270x it appeared as an obvious fuzzball -- very comet-like except for the color (slight off blue-green?).  There was a hint of a fan shape. This was the best magnification.  At 430x is was still obvious: quite large in the field, much easier and larger than in the past.

At the end of September 2003 I once again turned my scope north to Cepheus.  I was surprised to see the nebula appear obvious at 97x.  It looked very much like the comet (29P) I had just viewed, only brighter.  At 270x it was quite easy.  My crude drawing shows a fan-shaped nebula with PV Cep at one end.  PV Cep was quite bright as well, perhaps as bright as 13.5 magnitude.

In 2008 Dave Mitsky reported that in a 20-inch the nebula, "was extremely difficult to see at the time and resembled the streak seen in the 1952 photo...".  The photo he refers to is the second from the top above.  More recently, in August 2009 I had a look but failed to spot the nebula at all.  Although conditions were not perfect I expected to have seen something had it been as bright as earlier in the decade.

It's a pretty easy star hop to the nebula.  I usually start from 4 Cep.  From there the 7th magnitude star HD 198737 is in the same finder field.  Just to the west of this star lies a very distinctive quartile of stars.  Gyulbudaghian's Nebula lies just beyond.  If you don't see it at low magnification try something between 100-200x.  Look for a faint comet-like smudge of light near a faint star.  I have tried both an H-Beta and OIII filter, but both kill it completely.

Lastly, just in case you are wondering, Brian Skiff of Lowell Observatory suggest the following for the correct pronunciation of the nebula: "gyool-bu-dah-ghee-an" -- the first syllable sounds like "ghool" with a y sound and "dah" sounds like "father."

The diagram above simulates the view in an 18-inch telescope at 170x.  The field of view is 18.8'.  North is up and east is to the left.