It's a pair of F5 stars a little larger and hotter than the Sun, about 63 light-years away and shining in our sky at a combined magnitude
Because of this the combined magnitude
would have been approximately 5.5.
The Whirlpool and its mate shine at a combined magnitude
8.4 and have dimensions of roughly II' by 7'--relatively bright and large as galaxies go.
If more than one quake occurred simultaneously, the combined magnitude
could be 8, the governmental committee said.
Only a combined magnitude
is available for VV 102; the components are too tightly bound to measure separately.
I used differential aperture photometry in AIP4WIN to measure the combined magnitude
of Ganymede and Europa assuming a magnitude of 5.65 for Callisto as given by NASA.
That impression is not as strong in images, but M37 still looks darned good: a mob of small stars in a roughly spherical shape with a moderately bright combined magnitude
of 6.2 and a modest 14' diameter.
At a size of 14' across, M37 is well framed in almost any telescope, and the bright combined magnitude
of its stars, 5.6, makes it a showpiece.
The 10'-diameter NGC 6939 shines with a combined magnitude
of 10.1 and is well resolved in 8-inch and larger telescopes.
Their combined magnitude
is almost exactly -5, which is equal to 100 zero-magnitude stars like Vega.
Lalande 21185 UMa 7.5 4.80" 8.31 Sirius (A, B) CMa -1.4 * 1.33" 8.60 Luyten 726-8 (A, B) Cet 12.0 * 3.37" 8.73 Ross 154 Sgr 10.4 0.67" 9.69 Ross 248 And 12.3 1.62" 10.32 Epsilon Eridani Eri 3.7 0.98" 10.50 Lacaille 9352 PsA 7.4 6.90" 10.73 Ross 128 Vir 11.1 1.36" 10.89 * Combined magnitude
This would make the combined magnitude
for the unresolved pair of compact, high-surface-brightness galaxies magnitude 14.0, just within the 8-inch scope's reach.