CW Leonis, which is located 400 light-years away in the constellation of Leo, is a carbon star — a luminous type of red giant star with a carbon-rich atmosphere. Also known as IRC +10216 and LEDA 1427054, it has an orange-reddish color due to its relatively low surface temperature of 1,260 degrees Celsius (2,300 degrees Fahrenheit).
This Hubble image shows the carbon star CW Leonis. The image incorporates observations from 2011 and 2016 by Hubble’s Wide Field Camera 3 (WFC3). The star is brightest in the red filters, R and I, and therefore the simmering orange color pervading the center of the image well represents the real color of the star. Image credit: NASA / ESA / Hubble / T. Ueta / H. Kim.
“When small to intermediate-mass stars run out of hydrogen fuel in their cores, the outwards pressure that balances the crush of gravity within their cores falls out of equilibrium, causing the star to start collapsing,” Hubble astronomers said.
“As the core collapses, the shell of plasma surrounding the core becomes hot enough to begin fusing hydrogen, generating enough heat to dramatically expand the outer layers of the star and turn it into a bloated red giant.”
“Stars in that phase of life eject huge amounts of gas and dust outwards into space, eventually jettisoning their outer layers.”
In the case of CW Leonis, this process has surrounded the star with a dense pall of sooty dust.
“Along with CW Leonis’ smoky veil, the vibrant orange and green tints of this image make it a fitting celebration of Halloween,” the researchers said.
“The image resembles a single, baleful eye of cosmic proportions glaring out from within a cloud of smoke.”
“While these observations make for a striking image, they were originally made to answer pressing scientific questions about CW Leonis.”
CW Leonis gives astronomers the chance to understand the interaction between the star and its surrounding envelope.
This is a particularly interesting object to study as the envelope of CW Leonis is relatively turbulent, with a complex inner structure that astronomers believe may be sculpted by a nearby companion star.
“The bright beams of light radiating outwards from CW Leonis are one of the most intriguing parts of this image, as they’ve changed in brightness within a 15 year period — an incredibly short span of time in astronomical terms,” the scientists said.
“Gaps in the shroud of dust surrounding CW Leonis may allow these beams of starlight to pierce through and illuminate dust further from the star.”
“However, the exact cause of the dramatic changes in their brightness is as yet unexplained.”
“Detailed Hubble observations of CW Leonis taken over the last two decades also show the expansion of ring-like threads of ejected material around the star — CW Leonis’ sloughed-off outer layers.”
