88 Leonis
A wide binary near naked-eye visibility with a cycling primary star.
88 Leonis is a binary star system located in the equatorial constellation Leo. With a combined apparent magnitude of 6.2, it sits just above the threshold for naked-eye visibility. Based on parallax measurements, the system lies about 77 light-years from the Sun, though it is moving closer at a radial velocity of roughly −4.6 km/s. It also has a relatively high proper motion, crossing the sky at 0.379 arcseconds per year.
The primary star, component A, is an F-type main-sequence star classified as F9.5V, giving it a yellow-white hue. It has about 1.1 times the Sun’s mass and radius, and shines with 1.5 times the Sun’s luminosity from a photosphere at 5,990 K. Estimated to be 4.1 billion years old, it rotates once every 14.3 days. The star exhibits a short magnetic activity cycle averaging 3.5 years, along with a second cycle that has changed over time: it lasted 13.7 years when observations began, then decreased to 8.6 years over a 34-year span.
The secondary star, component B, has a magnitude of 9.22 and a spectral class of G5, with 69% of the Sun’s mass. It lies at an angular separation of 15.46 arcseconds from the primary, at a position angle of 326°. The two stars share a common proper motion, and their projected separation is about 360.6 astronomical units.
- Combined apparent visual magnitude
- 6.2
- Distance
- 77 light years
- Radial velocity
- −4.6 km/s
- Proper motion
- 0.379 arc seconds per annum
- Primary classification
- F9.5V
- Primary mass
- 1.1 solar masses
- Primary radius
- 1.1 solar radii
- Primary luminosity
- 1.5 solar luminosities
- Primary effective temperature
- 5,990 K
- Primary rotation period
- 14.3 days
Lore & Background
The system consists of a primary component A, a yellow-white hued F-type main-sequence star classified as F9.5V, and a secondary component B of class G5 with 69% of the Sun's mass. The primary is estimated to be 4.1 billion years old, spinning with a rotation period of 14.3 days, and radiates 1.5 times the Sun's luminosity from a photosphere at 5,990 K. It has a short magnetic activity cycle averaging about 3.5 years, while a second cycle has been observed to vary: it lasted 13.7 years at the start of observations then decreased to 8.6 years over a span of 34 years of measurement.
The secondary star has a magnitude of 9.22 and lies at an angular separation of 15.46″ from the primary along a position angle of 326°. The pair share a common proper motion through space, with a projected separation of 360.6 AU. The system is located at a distance of 77 light years from the Sun based on parallax, and is drifting closer with a radial velocity of about −4.6 km/s. It has a relatively high proper motion, traversing the celestial sphere at 0.379 arc seconds per annum.
Reader's Guide
88 Leonis is significant as a nearby wide binary system whose primary star exhibits complex magnetic activity cycles. The primary's short 3.5-year cycle and the longer, varying cycle (from 13.7 to 8.6 years over 34 years) provide a valuable case study for stellar magnetic behavior and cycle evolution. The system's common proper motion confirms the physical association of the two stars, with a projected separation of 360.6 AU. Its proximity at 77 light years and near-naked-eye visibility make it accessible for amateur and professional observation. The primary's F9.5V classification and solar-like properties (mass 1.1 M☉, radius 1.1 R☉, luminosity 1.5 L☉) allow comparisons with the Sun's own activity cycles. The secondary's G5 class and lower mass (69% solar) complement the system's diversity. The measured radial velocity of −4.6 km/s indicates the system is approaching the Sun, while its high proper motion of 0.379 arc seconds per year underscores its motion through the galaxy. These characteristics make 88 Leonis a useful target for studies of binary star dynamics and stellar activity.
Did You Know?
- A second magnetic cycle varied from 13.7 years to 8.6 years over 34 years of measurement.
- The secondary star has 69% of the Sun's mass and a spectral class of G5.
- The system has a projected separation of 360.6 AU between its two components.
More in Binary and Multiple Stars, Part 2 1-24
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