If a runaway star is massive and fast enough it can form a stellar bowshock. But what if the star moves into our direction or away from us? It has to look like an umbrella, seen from the top or the bottom.
This was the thought of EcceruElme, one of the moderators of the Milky Way Project (MWP). But how are they different from any other redball?
Redballs can be planetary nebulae, but they also include the umbrella bow-shock nebulae.
Umbrellas are different from any normal redball. They have a star, are asymmetric and sometimes you see a faint yellow bow inside.
But why do they appear as a redball in the MWP? The answer is that the MWP does produce images in a way so you can see the faintest and smallest structures. Bright and small structures appear, but they appear as a blob and you can’t see the structures anymore.
Even so EcceruElme was able to collect some “umbrellas”. At first I was a bit sceptical, but then I thought: “Maybe I can create my own images with the data and let the bow-shock appear.”
After my work was done, I was surprised. 38% of EcceruElmes umbrellas did appear as small bow-shocks.
We found 22 bow-shock candidates so far. About 50% appear in the bow-shock catalog in VizieR. It is the result of a great teamwork between EcceruElme and myself: She does find the umbrellas and I create the images. Please read in the project page of the Milky Way Project, if you want more details about them (like position and SIMBAD sources).
I want to present some of these bow-shocks here and compare them to the MWP images:
The umbrella bow-shock appears in the catalog with the sequence number 59:
This also appears in the catalog with the sequence number 70:
This is a new bow-shock: