# Different sizes of bow shocks

In this image of LL Ori bow shock,

there is a smaller bow shock at the upper right. Is that second bow shock substantially smaller than the LL Ori bow shock, or is it just much further away? If the stars are reasonably close, is the upper star significantly smaller that it is producing a much smaller bow shock? The LL Ori bow shock is measured about half a light-year across. Any estimates of the size of the smaller one?

After a bit of searching in Aladin. I found that the other star is V* V2170 Ori. By comparing their respective Simbad pages one can see the following:

• LL Ori is actually slightly further away. V2170 Ori has a GAIA parallax of 2.84 while LL Ori has one of 2.55. Simply using $$D=1/p$$, this translates to a distance of 0.35 kpc and 0.39 kpc

• LL Ori and V2170 Ori have about the same proper velocity of 1.65 and 1.69 mas/yr. So, that should affect the shock size.

• LL Ori is a lot brighter. It has an apparent V-Band magnitude of 11.5, while V2170 only has 18.7.

• LL Ori is hotter. Its spectral typ is K0-K3e, while V2170 is of spectral type M4.7e.

It is therefore not unexpected that LL Ori has a significantly stronger stellar wind and thus a larger bow shock.

Since the distance is basically the same, you can just have a look at this image with scale to estimate the size of the other bow shock.

• Thanks! I'd never heard of Aladin. Dec 4 '19 at 15:24