[10] Bayer had recorded χ Cygni as a 4th magnitude star, presumably near maximum brightness.

While researching that area of the sky for observations of Nova Vulpeculae, he noted that the star marked as χ in Bayer's Uranometria atlas was missing.

Thomas Dick, LL.D, writes:[13] "The particulars relating to it are, The star was then observed only sporadically until the 19th century.

[21] χ Cygni shows one of the largest variations in apparent magnitude of any pulsating variable star.

[23] The faster rise and bump are common features in the light curves of Mira variables with periods longer than 300 days.

[12] Longterm BAA and AAVSO data show minima consistently between about magnitude 13 and 14 throughout the 20th century.

[7] The annual parallax of χ Cygni has been calculated at 5.53 mas in the new reduction of Hipparcos satellite data, which corresponds to a distance of 590 light years.

[1] The distance can also be derived by comparing changes in the angular diameter with the measured radial velocity in the atmosphere.

This gives a parallax of 5.9 mas with a similar accuracy to the direct measurement, corresponding to a distance of 550 light years.

[30] The original parallax calculated from Hipparcos measurements was 9.43 mas, indicating a distance of 346 light years.

[7] χ Cygni is much larger and cooler than the sun, so large that it is thousands of times more luminous despite the low temperature.

[32] The visual magnitude of the star is closely correlated with the changes in the spectral type and temperature.

In the case of χ Cygni, its pulsations offer a way to directly measure the gravitation acceleration of layers in the atmosphere.

[7] χ Cygni is losing mass at a rate of nearly a millionth M☉ each year through a stellar wind at 8.5 km/s.

It also shows spectral lines from s-process elements such as technetium, produced naturally in AGB stars such as Mira variables.

[39] AGB stars become more luminous, larger, and cooler as they lose mass and the internal shells move closer to the surface.

They "ascend" the AGB until the mass loss becomes so extreme that they start to increase in temperature and enter the post-AGB phase, eventually to become a white dwarf.

[38] The evolution of a Mira variable should cause its period to increase, assuming it stays with the unstable region of pulsations.

[40][41] Thermal pulses on the TP-AGB produce progressively more dramatic changes until the end of the AGB phase.

The carbon-oxygen core of 0.6 M☉ will go on to become a white dwarf and the remaining envelope will be shed to possibly become a planetary nebula.