83 Leonis

Lore & Background

The primary component, 83 Leonis A, is a 6th magnitude star classified as a subgiant, meaning it has ceased fusing hydrogen in its core and is evolving toward red gianthood. It is not visible to the unaided eye but is easily seen with small binoculars. The secondary component, 83 Leonis B, is an 8th magnitude orange dwarf, somewhat less massive (0.88 MSun), smaller, and cooler than the Sun, visible only with binoculars or better equipment. The two stars share common proper motion, confirming them as a physical pair; the projected separation is 515 AU, but the true separation may be much higher. A third, magnitude 14.4 component listed in the Washington Double Star Catalog is moving in a different direction and is not a true member of the system.

Reader's Guide

The 83 Leonis system is significant as a binary star system that hosts a confirmed exoplanet, discovered in January 2005 by the California and Carnegie Planet Search team using the radial velocity method. The planet, designated 83 Leonis Bb, has a minimum mass less than half that of Saturn and orbits very close to the secondary star, completing one orbit in about 17 days. A second planet claimed in 2010 was found to be a false positive in 2016, but a different second planet was discovered in 2023, also given the designation 'c'. The system's primary and secondary stars are both presumed to be cooler than the Sun. The binary nature and the presence of a planetary companion make 83 Leonis a valuable target for studying planet formation and evolution in multiple-star systems.

Did You Know?

• The primary star is a subgiant that has stopped fusing hydrogen in its core.
• The secondary star has 0.88 times the mass of the Sun.
• The exoplanet 83 Leonis Bb has an orbital period of about 17 days.
• A second planet claimed in 2010 was later found to be a false positive.