55 Cancri e
55 Cancri e (also known as Janssen) is a fascinating exoplanet located approximately 41 light-years from Earth in the constellation Cancer. Discovered in 2004, it was the first super-Earth—a class of planets more massive than Earth but lighter than Uranus or Neptune—to be found orbiting a Sun-like star, 55 Cancri A .
🔭 Key Facts
Mass: About 8 Earth masses
Radius: Approximately 1.9 times Earth's radius
Orbital Period: Completes an orbit around its star in just 18 hours
Surface Temperature: Can reach up to 4,892°F (2,700°C)
Distance from Star: Orbits at a distance of 0.015 AU, making it extremely close to its host star
🌋 Surface and Atmosphere
55 Cancri e is a tidally locked planet, meaning one side always faces its star while the other remains in perpetual darkness. The day side is intensely hot, likely covered by a magma ocean. The night side, cooler by comparison, may harbor a solid crust .
Recent observations by the James Webb Space Telescope (JWST) have revealed that the planet possesses a substantial atmosphere, primarily composed of carbon dioxide (CO₂) and carbon monoxide (CO). This atmosphere is likely sustained by volcanic outgassing from the planet's molten surface .
💎 Composition and Structure
While earlier studies suggested that 55 Cancri e might be rich in carbon, possibly containing large amounts of diamond, more recent research indicates that its composition is more complex. The planet's extreme temperatures and proximity to its star have likely led to significant atmospheric loss over time .
🔭 Observations and Discoveries
2004: Discovered via radial velocity measurements, marking it as the first super-Earth found around a main-sequence star .
2011: The MOST space telescope confirmed the planet's transit across its star, providing further insights into its size and composition.
2024: JWST observations confirmed the presence of a substantial atmosphere, rich in carbon-based molecules .
🌌 Why It Matters
55 Cancri e offers a unique opportunity to study the characteristics of super-Earths, particularly those that are tidally locked and have extreme surface conditions. Understanding such planets can provide valuable insights into planetary formation, atmospheric dynamics, and the potential for habitability in other star systems.