In August 2021, our team discovered this large object with an apparent size of 13.5 arcminutes, equivalent to about half a full moon in the night sky.

The nebula is located in the constellation Unicorn, near the famous Monoceros Loop and only 1.2 degrees away from another discovery of our team, the spectroscopically confirmed planetary nebula Strottner-Drechsler 13 (PNG 204.4-00.4).
This new object was added to our catalog by Pascal Le Dû - with the reference Strottner-Drechsler 155.

This object of unknown nature is located in the heart of a very complex region of nebulae and MIR.
The H-alpha signal of the nebula turns out to be extremely faint. [OIII], on the other hand, is very dominant, with a distinct southern periphery.



The possible central star is slightly decentered and has an intense blue color, indicating an extremely high temperature.
This hot star could be responsible for the ionization of the structure. A precise indication of the distance and temperature of the star cannot be given due to insufficient data.

Similarities to other recently discovered objects are striking, including Hu6 (Laurent Huet), Fal Object 1 (Bray Falls) or StDr Object 33, all of which have in common that they are very large [OIII] structures whose origin remains unclear.


Hu6 (Laurent Huet)


Fal Object 1 (Bray Falls) 


StDr Object 33 (Marcel Drechsler and Xavier Strottner)

So the nature of this gas cloud remains unclear - the creation of a spectrum would bring new insights and allow an accurate classification of the nebula.

This nebula was imaged by our friends of the Astrofleet team from their setup in Spain. 
A big thank you!


Discoverers: Xavier Strottner, Marcel Drechsler
Data acquisition: Team Astrofleet
Image processing: Marcel Drechsler

*


Object data
Designation: StDr 155 / PN-G: 203.1-00.3
Coordinates: 06:32:24.58 +08:32:11.46
Diameter: 13.5 arc min