In article , "Phillip Helbig (undress to
reply)" writes:

Right: back issue of the ApJ, or bricks. :-) Right, we don't know
whether it consists of microscopic objects, but if so, presumably it
would have to be self-interacting with a cross section much larger than
for the weak interaction.

Microscopic --- macroscopic. If it consists of macroscopic objects,
they have to be held together, which implies some sort of
self-interaction. (The self-interaction could be gravity, but if
gravity is the only force involved, it is more difficult to form
objects, since accretion is efficient only after a certain mass has been
reached, and in order to reach this, one needs some other mechanism to
make bits of the object stick together and/or some mechanism for
cooling. Black holes are possible, but have been ruled out
observationally in many mass ranges.)