CW Leonis

CW Leonis, also known as IRC +10216, is a remarkable variable carbon star. It is currently hidden inside a very thick envelope of dust. This star is a vital subject for astronomers studying how stars change. It is believed to be in a late stage of its life cycle. The star is currently blowing off its own sooty atmosphere. Eventually, this process will result in the formation of a white dwarf. A white dwarf is a small, dense remnant of a star.

The star functions through a process called pulsation. It follows a regular pulsation cycle that lasts 649 days. During this cycle, the star's bolometric luminosity, or total energy output, changes significantly. The luminosity ranges from a minimum of about 6,250 times the luminosity of our Sun. At its peak, the output reaches approximately 15,800 times the Sun's luminosity. This variation causes the star's brightness to change by about two magnitudes. Because the star is very red, scientists often study it using infrared wavelengths.

The physical structure surrounding the star is quite complex. CW Leonis is embedded in a large, carbon-rich gaseous envelope. This dust envelope is at least 69,000 years old. It contains at least 1.4 solar masses of material. Observations from 1999 using speckle techniques revealed a complex structure within this dust. The envelope includes partial arcs and unfinished shells. This clumpiness might be caused by a magnetic cycle within the star. Such a cycle could be similar to the solar cycle seen in our Sun. This cycle may lead to periodic increases in mass loss.

Astronomers first identified this object in 1969. A team led by Eric Becklin made the discovery. They used infrared observations from the 62-inch Caltech Infrared Telescope. This telescope was located at the Mount Wilson Observatory. The star is particularly notable for its energy emission. At a wavelength of 5 μm, it has the highest flux of any object outside our Solar System. This high flux makes it a primary target for infrared astronomy.

We can learn a lot about the star's history from its mass. Based on the isotope ratios of magnesium, scientists have estimated its original size. The initial mass of the star was likely between 3 and 5 solar masses. However, the star is losing mass rapidly. It is losing about one solar mass per year. The core of the star is much smaller than its original size. The core mass is estimated to be between 0.7 and 0.9 solar masses. This core will eventually become the white dwarf.

Chemical analysis of the outflows from CW Leonis shows incredible variety. Scientists have detected about 50 different molecules in these outflows. These include elements such as nitrogen, oxygen, silicon, and iron. Water has also been detected in these outflows. One old theory suggested that comets melted as the star expanded. However, scientists now believe water forms naturally in the atmospheres of all carbon stars. This discovery helps us understand the chemistry of dying stars.

CW Leonis is also a very fast-moving object in space. It travels through the interstellar medium at a velocity of more than 91 km/s. If we assume the distance to the star is 120 pc, its astrosphere is enormous. The radius of this surrounding area would span about 84,000 AU. Additionally, some research suggests the star may have a close binary companion. Measurements from ALMA and astrometric data show possible orbital motion. This suggests the star might not be alone in its system. These studies also indicate that CW Leonis is the closest carbon star to Earth.