Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. HD 17156 is a yellow subgiant star approximately 255 light-years away in the constellation of Cassiopeia. The apparent magnitude is 8.17, which means it is not visible to the naked eye but can be seen with good binoculars. The Sun to star distance is 255.19 ly or 78.24 pc. The mass of the star is 20% more massive and 47% larger than our Sun. Based on its absolute magnitude of 3.70 and spectral type of G0, the star is thought to be hotter than the Sun. Based on the chromospheric observations, it was found that the age is 5.7 ± 1.3 billion years. The total lifetime of a 1.2 sol mass star should be 1.2 -2.5 × 1010, which is under 6.4 billion years; this star is in the last stage on the main sequence, and its nearby planets will soon be engulfed.