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
Pearson symbol more commonly used hexagonal setting has 3 translation equivalent points per unit cell. The Pearson symbol refers to the hexagonal setting in its letter code ("hR") but the following figure gives the number of translation equivalent points in the primitive rhombohedral setting. Examples: "hR"1 and "hR"2 are used to designate the Hg and Bi structure, respectively. The Pearson symbol should only be used to designate simple structures (elements, some binary compound) where the number of atoms per unit cell equals, ideally, the number of translation equivalent points. Pearson symbol The Pearson symbol, or Pearson notation, is used in crystallography as