19 Aquarii 19 Aquarii 19 Aquarii is a star in the constellation of Aquarius. With an apparent magnitude of about 5.7, the star is barely visible to the naked eye (see Bortle scale). Parallax estimates made by the Hipparcos spacecraft put it at a distance of about 300 light years (92 parsecs) away from the Earth. 19 Aquarii has a spectral type of A8V, meaning it is an A-type main-sequence star. These types of stars are bluish-white colored, and have effective temperatures between 7100 and 11500 K. It rotates fairly fast, as its projected rotational velocity is about 155 km/s, so it
Unit distance graph such graphs can be colored with at most seven colors. Another important open problem concerning unit distance graphs asks how many edges they can have relative to their number of vertices. The following graphs are unit distance graphs: Any Cartesian product of unit distance graphs produces another unit distance graph. However, the same is not true for other commonly-used graph products . Some sources define a graph as being a unit distance graph if its vertices can be mapped to distinct locations in the plane such that adjacent pairs are at unit distance apart, disregarding the possibility that some non-adjacent