• Key Information

  • 40 Eridani

  • Type
    Star System (Trinary)
  • Diameter
    702,034 miles (A), 12,104 miles (B), 268,018 miles (C)
  • Distance from Sun
    16.34 light years
  • Mass
    0.78 M☉ (A), 0.57 M☉ (B), 0.20 M☉ (C)
  • Star Type
    K0.5V - Orange Mainstream (A), DA4 - White Dwarf (B), M4.5eV - Red Dwarf
  • Temperature
    8,670 °F (A), 29,240 °F (B), 5,120 °F (C)
  • Date of Discovery
    Unknown
  • Other Names
    Omicron² Eridani,, Keid (A), HD 26965 (A), HIP 19849 (A), HR 1325 (A)
  • Learning Point
  • 40 Eridani is a triple star system quite close to our Solar System, containing the first white dwarf that was ever discovered, and one of the easiest to see in the night sky. The system may well be able to support planets within the habital zone of the main star.
  • Project
  • Draw a diagram of the 40 Eridani system. Discuss what might make a triple/trinary star system unworkable.
  • Location
  • Located in
    Eridanus
  • Fun Facts
  • Triple star systems are most commonly contructed of a pair of stars orbiting or bring orbited by a single star.
  • When the second star (B) collapsed into a white dwarf, it would likely have destabilised or damaged any orbiting planets around it.
  • If a planet was in the habitable zone of the main star, it would orbit in around 200 days, and the star would be 20% in the sky of the planet compared to our Sun.
  • Before the second star (B) collapsed, it would have been the main star in the system, but its collapse resulted in it losing a lot of its mass.