This star is one of the most remarkable variables known.

Its period is 12d.21h.53m.10s.In this time it passes from a maximum brilliancy--that of a star of the 3.4 magnitude--to a minimum lustre equal to that of a star of the 4.3 magnitude, thence to the same maximum brilliancy as before, thence to another minimum of lustre--that of a star of the 4.5 magnitude--and so to its maximum lustre again, when the cycle of changes recommences.
These remarkable changes seem to point to the existence of two unequal dark satellites, whose dimensions bear a much greater proportion to those of the bright components of [beta] Lyrae than the dimensions of the members of the Solar System bear to those of the sun.

In this case, at any rate, the conjecture hazarded about Algol, that the star revolves around a dark central orb, would be insufficient to account for the observed variation.
Nearly midway between [beta] and [gamma] lies the wonderful ring-nebula 57 M, of which an imperfect idea will be conveyed by the last figure of Plate 3.

This nebula was discovered in 1772, by Darquier, at Toulouse.
It is seen as a ring of light with very moderate telescopic power.

In a good 3-1/2-inch telescope the nebula exhibits a mottled appearance and a sparkling light.