The neutrinos can't have any mass.

After a trip of 150 000 years, the neutrinos from SN87A arrived
several hours BEFORE the photons.

Since nothing with mass can't travel faster than light, this means
that they can't have any rest mass.

Now, it can be argued that neutrinos come from the center of the
explosion directly, without suffering any delay since they traverse
the star unhindered. Photons can be slowed down by the dense upper
layers of the star, but they had 150 000 years to catch up with the
neutrinos!

Is this reasoning sound?

Suppose that the photons had such a delay that they couldn't catch
up completely in 150 000 years and they arrived several hours too
late here. Does this impose an upper bound into the neutrino mass?

Would it be feasible since we know the diameter of the precursor
star to calculate the delay for the photons?

Reading arXiv:1008.4726v1 [hep-ph] 27 Aug 2010 ("What is the Issue
with SN1987A Neutrinos?") I see a lot of issues but this specific
question is not even mentioned.

My conclusion is that I am missing something fundamental but...
What?

I do not know. Thanks for any replies.

Thanks for your attention.

[[Mod. note --
What we think
https://en.wikipedia.org/wiki/SN_1987A#Neutrino_emissions
is that the neutrino burst was emitted simultaneously with the core
collapse. It then took several hours for the shock wave to travel
out to the star's surface; the optical light signal from the supernova
wasn't emitted until the shock wave reached the star's surface.
-- jt]]