  Space telescope observations of massive black holes during their formation
may be key to understanding the origin of supermassive black holes and
high-redshift quasars. To create diagnostics for their detection and
confirmation, we study a simulation of a nascent massive, so-called
direct-collapse, black hole that induces a wave of nearby massive metal-free
star formation, unique to this seeding scenario and to very high redshifts.
Here we describe a series of distinct colors and emission line strengths,
dependent on the relative strength of star formation and black hole accretion.
We predict that the forthcoming James Webb Space Telescope might be able to
detect and distinguish a young galaxy that hosts a direct-collapse black hole
in this configuration at redshift 15 with as little as a 20,000-second total
exposure time across four filters, critical for constraining supermassive black
hole seeding mechanisms and early growth rates. We also find that a massive
seed black hole produces strong, H$_2$-dissociating Lyman-Werner radiation.
