Evidence of Extreme Pre-Explosion Mass Loss in Supernova Challenges Stellar Evolution Theory
A newly discovered supernova, known as SN 2023ixf, is causing a stir among astronomers due to its extreme pre-explosion mass loss, challenging the standard theory of stellar evolution. This unexpected behavior provides valuable insight into the final year of a star’s life before it explodes.
SN 2023ixf, a Type II supernova, was discovered in May 2023 by amateur astronomer Kōichi Itagaki of Yamagata, Japan shortly after its progenitor star exploded. Located in the Pinwheel Galaxy, about 20 million light-years away from Earth, SN 2023ixf offers scientists a unique opportunity to study the death of massive stars in supernova explosions.
Type II supernovae occur when red supergiant stars, ranging from eight to 25 times the mass of the Sun, collapse under their own weight and explode. However, SN 2023ixf’s behavior did not align with the typical expectations for this type of supernova. Follow-up observations led by astronomers at the Center for Astrophysics | Harvard & Smithsonian (CfA) revealed unprecedented mass loss in the star prior to its explosion.
In the year leading up to the supernova, SN 2023ixf shed an unexpected amount of mass equivalent to the mass of the Sun. This extreme mass loss, which is not characteristic of Type II supernovae, challenges astronomers’ understanding of the evolution of massive stars. The observations suggest that there may be instability in the final years of a star’s life, leading to such significant mass loss. This phenomenon could be linked to the final stages of nuclear burn-off of high-mass elements in the star’s core.
One remarkable aspect of SN 2023ixf was its delayed shock breakout. Typically, within hours of going supernova, core-collapse supernovae emit a flash of light when the shock wave from the explosion reaches the outer edge of the star. However, SN 2023ixf’s shock breakout was delayed by several days, providing direct evidence for the presence of dense material from recent mass loss.
To better understand this phenomenon, a team of scientists led by CfA postdoctoral fellow Daichi Hiramatsu analyzed data from various telescopes, including the 1.5m Tillinghast Telescope, 1.2m telescope, and MMT at the Fred Lawrence Whipple Observatory. They also utilized data from the Global Supernova Project. This multi-wavelength study, published in The Astrophysical Journal Letters, revealed the significant mass loss and the delayed shock breakout of SN 2023ixf.
Further observations conducted by Edo Berger, a professor of astronomy at Harvard and CfA, using the Submillimeter Array (SMA) in Hawai’i, tracked the collision between the supernova debris and the dense material lost before the explosion. This data, also published in The Astrophysical Journal Letters, sheds light on the behavior of massive stars in the final years of their lives.
The discovery of this supernova and the collaboration between amateur and professional astronomers have significant implications. The partnership allowed for timely observations and investigations that provided critical understanding of the evolution of massive stars and their explosions. Amateur astronomer Kōichi Itagaki’s swift discovery and collaboration with CfA astronomers played a pivotal role in acquiring vital data.
SN 2023ixf continues to be monitored, and astronomers anticipate further discoveries that will deepen our understanding of stellar evolution and supernova explosions. By studying young supernovae like SN 2023ixf, scientists can piece together the puzzle of a star’s life leading up to its explosive demise.
References:
– “From Discovery to the First Month of the Type II Supernova 2023ixf: High and Variable Mass Loss in the Final Year before Explosion”
– “Millimeter Observations of the Type II SN 2023ixf: Constraints on the Proximate Circumstellar Medium”