NGC 7789 is an open cluster in Cassiopeia that was discovered by Caroline Herschel in 1783. Her brother William Herschel included it in his catalog as H VI.30. This cluster is also known as "The White Rose" Cluster or "Caroline's Rose" Cluster because when seen visually, the loops of stars and dark lanes look like the swirling pattern of rose petals as seen from above.
WY Cassiopeiae (WY Cas) is a variable star in the constellation Cassiopeiae ( Check
http://epod.usra.edu/blog/2009/02/amazing-variable-star-in-constellation-cassiopeiae.html). WY Cassiopeiae is an S-type star (red giants of spectral type S similar to those of type M, except that the dominant oxides in its spectrum are those formed by metals of the fifth period of the periodic table (zirconium, yttrium, etc.) instead of those of the fourth period (titanium, scandium and vanadium)) with a surface temperature of only 2200 K. Its luminosity is 6700 times greater than the solar luminosity.
It currently loses stellar mass at the rate of 2.26 × 10-6 solar masses per year. Another characteristic of these stars is their large size; the radius of WY Cassiopeiae is ~575 times larger than the solar radius, equivalent to 2.7 AU; if it were in the Sun's place, the orbits of the four inner planets would be encompassed within the star.
WY Cassiopeiae is a Mira variable whose brightness varies between magnitude +10.0 and +16.9 over a period of 476.56 days. In these variables - whose prototype is the well-known Mira (ο Ceti) - instability comes from pulsations on the stellar surface, causing changes in color and brightness. Some of them, including R Cassiopeiae, S Cassiopeiae as well as WY Cassiopeiae itself, show a SiO maser emission.
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