This complex spectral data represents pecularities in the star's chemistry. The chemical signature of the star indicates an abundance of CN, CH and C2 molecules.
This is thought to occur in some binary systems when there is a close companion whose mass has been transferred to the recipient star. The doner is left as a white dwarf while the recipient becomes what is called a barium star.
In this case, the barium star is 18 Draconis, the bright yellow star we can see in the image. The companion donar star is lost in the glare and does not appear in the photo.
There is another unusual star in this image. Directly below 18 Draconis, roughly halfway the distance to the bottom of the image is a small blue star.
This star is interesting because most stars commonly described as blue are actually far more white than blue.
Generally, blue looking stars are better described as white stars with a "cool white" hue similar to white light from an LED or fluorescent lamp. And those types of stars are very common indeed.
But a truly blue star is less common. So when a genuine blue star appeared in this image, it prompted me to look it up to see if there was anything listed about it.
Turns out the star has in fact been cataloged and is in SIMBAD. Is it listed as being PG 1640+645, a hot subdwarf. A close up image of this star was cropped from the original data and is included here. It is very blue indeed compared to almost all the other stars in this image including 18 Draconis.
These two images show where PG 1640+645 can be found in the main photo above. The highlighted area is about half way between 18 Draconis in the center and the bottom of the image.
For those interested in hot blue subdwarves (and who isn't), a hot subdwarf is the compacted helium core of a late stage red giant. And in this case the leftover core turned out to be blue.
This occurs when the giant prematurely loses it's surrounding hydrogen layers to space. The exact reasons for this occuring are unknown at present. Most cases seem to involve interaction with another star in binary systems where the combined gravitational influences helps remove material from the giant.
Regardless of the cause, the end result is a distinctly blue star with the unusual spectral type of sdB0VIIHe9. It is magnitude 14.92 and is of type sdB which means it is more luminous than a normal white dwarf.
It turns out that there is an entire genre for blue things in space and this star is blue enough that it is considered to be a blue stellar object (BSO). More information on this star and other blue stellar objects can be found in the Revised and Updated Catalogue of the First Byurakan Survey Blue Stellar Objects (2008, Mickaelian, A. M.).
More Blue Stuff
There is yet another blue stellar object in the main photo. Below is a cropped image from the upper left corner that shows FBS 1645+649.
This star appears as the small blue dot near the larger and brighter white star. If you zoom in on the main image above and look around in the upper left corner, the blue star is fairly easy to spot.FBS 1645+649 is also found in the Byurakan Survey catalog. It is very faint at magnitude 15.9 and is cataloged in SIMBAD as being a high proper motion star. There is no information available I could find on why it is so blue.
The white star near FBS 1645+649 is not directly listed in SIMBAD. But it does have a 2MASS designation and listed in VizieR as 2MASS 16452304+6453267.
The 2MASS reference for the white star can be also located in VizieR using RA and DEC search coordidnates. And it even has a USNO J1645231+645326 designation. But I could not find a record for it in the main SIMBAD query system.
