CW Leonis, also catalogued as IRC+10216, is a well-studied carbon-rich red giant located in the constellation Leo. It is an evolved star on the asymptotic giant branch (AGB) that has produced a thick, dusty envelope of carbonaceous material. This surrounding shell absorbs visible light and re-radiates strongly at longer wavelengths, making CW Leonis one of the brightest stellar objects in the sky at infrared wavelengths and an important subject for observers working in infrared astronomy.
Characteristics
The star is significantly larger than the Sun—roughly several hundred times the Sun's radius—and it is losing mass at a high rate through a slow, dense stellar wind. At its surface and in the surrounding gas, chemistry driven by an excess of carbon forms molecules and dust grains. CW Leonis is classified as a carbon star, meaning carbon-bearing molecules dominate its spectrum rather than oxygen-rich species.
Observations have revealed a complex, clumpy circumstellar envelope containing dozens of molecular species and solid particles. High-resolution imaging and spectroscopy show temporal variability and structure in the outflow, indicating irregular mass ejections and dust formation zones at different radii from the star.
Evolution and discovery
As an AGB star, CW Leonis is in a late stage of stellar evolution: it has exhausted core hydrogen and helium and now burns shells of fuel while expanding and cooling. Over time it will shed much of its envelope and eventually leave behind a white dwarf surrounded by a planetary nebula. The object entered modern astronomical catalogs when infrared surveys and spectroscopic work identified its unusual spectrum and strong infrared flux; it later received the variable-star designation CW Leonis.
Scientific importance and notable facts
- Key laboratory for circumstellar chemistry: observers have detected a rich inventory of molecules, from simple diatomics to more complex carbon chains, making the star important for astrochemistry.
- Dust production and mass loss: the star provides insights into how evolved stars seed the interstellar medium with carbon-rich dust that contributes to future generations of stars and planets.
- Bright infrared source: because its visible light is largely absorbed by dust, CW Leonis is primarily studied with infrared and radio facilities.
Because of its brightness in the infrared and its chemically rich envelope, CW Leonis continues to be a frequent target for ground- and space-based observatories. Its behavior illustrates key processes in the final, mass-losing phases of low- to intermediate-mass stars and helps link stellar evolution with the chemistry of the galaxy.