CASEY REED STELLAR FRONTIERS by Ken Croswell FAMILY PORTRAIT A trio of stars make up 40 Eridani, all of which are fainter and smaller than the Sun: 40 Eridani A, an orange dwarf (foreground); 40 Eridani B, a white dwarf so hot it's actually blue; and 40 Eridani C, a red dwarf, the most common type of star in the galaxy. The white dwarf is only 43% larger than Earth's diameter. 28 DECEMBER 2022 * SKY & TELESCOPE