Close-up View of a Rare Nearby Supernova Sheds Light on Stellar Deaths

For centuries, astronomers have been captivated by the grand finales of the universe’s most massive stars, supernovae. These cosmic detonations are not only incredibly spectacular, with the power to outshine our sun by up to 5 billion times, but they also play a crucial role in scattering precious elements like gold, silver, and zinc across the cosmos. These elements can only be crafted during the final breaths of a dying star.

Furthermore, this particular supernova, officially labeled SN 2023ixf, had an ideal position in the night sky, making it accessible to astronomers shortly after its eruption.

Traditionally, scientists lack the ability to anticipate when a star will meet its end. Consequently, they rarely have access to numerous images captured shortly after a supernova event, according to Edo Berger, an astronomer at Harvard University. However, the fortunate location of this supernova in a nearby galaxy well-known to amateur astronomers allowed researchers to utilize images taken by these enthusiasts. This data was instrumental in precisely determining the star’s explosion time, a task in which astronomer Daichi Hiramatsu, also from Harvard, played a pivotal role.

Possessing data on a supernova’s explosion shortly after its occurrence is of paramount importance in resolving numerous lingering inquiries regarding the final stages of a star’s life. Here are three key aspects to comprehend about this remarkable supernova event.

SN 2023ixf was formerly an obscured red supergiant enshrouded in dust

SN 2023ixf came to attention through the discovery by amateur astronomer Koichi Itagaki, who spotted the supernova just days after its explosive birth. Following this finding, scientists wasted no time delving into archived astronomical data to identify the star that had preceded this remarkable event. According to astronomer Charlie Kilpatrick from Northwestern University in Evanston, Illinois, the process of investigating the supernova’s history began within hours of receiving the initial report.

Almost immediately, Kilpatrick and his team made a serendipitous discovery while examining Hubble Space Telescope images of the Pinwheel galaxy captured between 5 and 24 years before the supernova’s explosion. They detected what seemed to be the star, known as the supernova progenitor, which eventually gave rise to SN 2023ixf. This discovery was indeed fortunate, as at the time the Hubble images were taken, no one had foreseen the star’s imminent detonation. Subsequently, several other research groups utilized images from different telescopes to independently verify the identity of SN 2023ixf’s progenitor, confirming it as a red supergiant concealed beneath a dusty shroud.

Progenitors like this red supergiant star are frequently associated with explosions such as SN 2023ixf, according to Kilpatrick. He also emphasizes that, in many respects, SN 2023ixf can be considered a typical supernova.

Berger highlights the value of studying a supernova like SN 2023ixf, which represents the typical way that most stars meet their end. While unique supernovas can be captivating, understanding the common mechanisms of stellar death is essential for advancing our knowledge of stellar evolution.

In its last phase, SN 2023ixf underwent a dramatic process of mass loss

Examining the deaths of stars involves a kind of astronomical forensic analysis, explains Berger. Stars die, but their deaths aren’t directly observable. “Then you kind of have to backtrack what the star was doing all the way up to that point,” he says. “And tracking how the star was losing mass is a critical part of that.”

Berger and Hiramatsu have just released findings indicating that the star which turned into SN 2023ixf experienced an astonishing loss of mass in its last years—equivalent to the mass of an entire sun, a significantly higher amount than anticipated.

To piece together the intricate details of this stellar demise, the scientists closely examined the light emitted during SN 2023ixf’s explosion. When the star imploded, it generated a shock wave that produced a brilliant burst of light upon striking the materials surrounding the star, including the mass it had shed prior to the explosion. By utilizing the explosion’s luminance to chart this material, the team could reconstruct the rates at which SN 2023ixf lost mass in the period leading up to its spectacular explosion.

Red supergiant stars are recognized for shedding mass before a supernova event, but the mass loss observed in the final years preceding the recent SN 2023ixf explosion was substantially greater, according to Hiramatsu. This suggests that something exceptional occurred to the progenitor star of SN 2023ixf—something that could also be relevant to other stars. Despite this discovery, the precise mechanisms behind this phenomenon remain a mystery to researchers.

Berger notes that our current understanding of stellar evolution theory falls short in explaining the specifics of these final moments in a star’s long existence. To unravel the mysteries of a star’s demise, “we need to rely on the data we can gather,” he explains. This supernova presents a unique opportunity to collect crucial data in this regard. Kilpatrick expresses his excitement, highlighting that this is an exceptional opportunity for research.

SN 2023ixf marks the closest supernova observed in the multi-messenger age

In the past, astronomers had to rely solely on the light from a supernova as their primary source of information. However, according to astrophysicist Zidu Lin from the University of Tennessee, Knoxville, having just one form of information isn’t sufficient to unveil the enigmas of these collapsing stars. Lin specializes in neutrinos, elusive subatomic particles that have minimal interactions with matter, making them an additional vital avenue of study.

Presently, scientists have the capability to detect elusive neutrinos and gravitational waves emanating from specific celestial phenomena, potentially including events like the stellar explosion of SN 2023ixf. This supernova, situated a bit beyond 21 million light-years from us, is the nearest of its kind to grace the night sky during the modern era of “Multi-messenger” astronomy. Although our current technology lacks the precision required to capture gravitational waves or low-energy neutrinos from supernovas outside the Milky Way, including SN 2023ixf, the detection of a few high-energy neutrinos originating from supernovas in nearby galaxies, such as the Pinwheel, is indeed achievable.

Given this context, it was somewhat unexpected that no high-energy neutrinos were detected originating from SN 2023ixf, as researchers disclosed in September. The absence of these neutrinos, in conjunction with certain optical signals, might furnish the basis for a multi-messenger analysis. This approach could be particularly valuable in helping astronomers refine their understanding of the precise mechanisms responsible for generating high-energy neutrinos within stars as they approach the end of their life cycles.

Resources

1. ^NEWSPAPER Cutts, E. (2023, October 23). A rare glimpse at a relatively nearby supernova offers clues to how stars die. Science News. [Science News]
2. ^JOURNAL Kilpatrick, C. D., Foley, R. J., Jacobson-Galán, W. V., Piro, A. L., Smartt, S. J., Drout, M. R., Gagliano, A., Gall, C., Hjorth, J., Jones, D. O., Mandel, K. S., Margutti, R., Ramírez-Ruiz, E., Ransome, C. L., Villar, A., Coulter, D. A., Gao, H., Matthews, D. J., Taggart, K., & Zenati, Y. (2023). SN 2023IXF in Messier 101: a variable red supergiant as the progenitor candidate to a Type II supernova. The Astrophysical Journal, 952(1), L23. [The Astrophysical Journal]
3. ^JOURNAL Hiramatsu, D., Tsuna, D., Berger, E., Itagaki, K., Goldberg, J. A., Gómez, S., De, K., Hosseinzadeh, G., Bostroem, K. A., Brown, P. J., Arcavi, I., Bieryla, A., Blanchard, P. K., Esquerdo, G. A., Farah, J., Howell, D. A., Matsumoto, T., McCully, C., Newsome, M., . . . Wheeler, J. C. (2023). From Discovery to the First Month of the Type II Supernova 2023ixf: High  and Variable Mass Loss in the Final Year before Explosion. arXiv (Cornell University). [arXiv (Cornell University)]
4. ^JOURNAL Guetta, D., Langella, A., Gagliardini, S., & Della Valle, M. (2023). Low- and High-energy Neutrinos from SN 2023ixf in M101. The Astrophysical Journal, 955(1), L9. [The Astrophysical Journal]
5. ^JOURNAL Berger, E., Keating, G. K., Margutti, R., Maeda, K., Alexander, K. D., Cendes, Y., Eftekhari, T., Gurwell, M. A., Hiramatsu, D., Ho, A. Y. Q., Laskar, T., Rao, R., & Williams, P. K. G. (2023). Millimeter observations of the Type II SN 2023IXF: Constraints on the proximate circumstellar medium. The Astrophysical Journal, 951(2), L31. [The Astrophysical Journal]