Original | Evan Gough
Translate | Linvo
This is another innovation in astronomy.
Recently, for the first time, astronomers have taken a real-time image of the end of life of a red supergiant. They witnessed the star's dying struggle before it finally exploded into a supernova. The observations differ from previous theories about the behavior of the red giant before they exploded.
A group of astronomers passed through two observatories in Hawaii: the Pan-STARRS Observatory in Hareakala, Maui, and the W. W. Miller Observatory in Monakia, Hawaii. M. Keck Observatory, observing this dramatic change. Their observations are part of the Young Supernova Experiment (YSE) transient observations. They observed the explosion of the supernova called SN 2020tlf for the last 130 days before the explosion.
The paper presenting the discovery is titled "Last Moments: Precursor Emission and Surface Expansion of a Luminous Type II Supernova 2020tlf Before Mass Loss Enhancement." The paper, published in the Astrophysical Journal, features Wynn Jacobson-Galán, an NSF graduate researcher at the University of California, Berkeley.
Jacobson-Galán said in a press release: "This is a breakthrough in our understanding of what massive stars will do before they die. "Pre-supernova activity was detected directly in a red supergiant star, and has never been observed before in an ordinary Type II supernova." For the first time we saw a red supergiant explode!"
The discovery dates back to the summer of 2020. At that time, the luminosity of the protostar rose sharply. Pan-STARRS detected this brightening phenomenon, and when autumn came, the star exploded into what is now SN 2020tlf. This supernova is a Type II supernova, in which a massive star undergoes rapid collapse and then explodes.
The team used Keck Observatory's Low-Resolution Imaging Spectrometer (LRIS) to capture the supernova's first spectrum. LRIS's data shows that when a star explodes, it is surrounded by material surrounding the star. This material is likely to have been seen by a pan-star observation system in the summer before the star exploded.
"Keck has been instrumental in providing direct evidence of massive stars turning into supernova explosions," said senior author Raffaella Margutti, an associate professor of astronomy at the University of California, Berkeley. "It's like watching a ticking time bomb. We've never confirmed such intense activity in a dying red giant, and we've seen it produce such bright emissions, then collapse and burn until now. ”
The data shows how the supernova exploded. Green is the sum of all wavelengths of electromagnetic radiation, red is the temperature of blackbody radiation, and blue is the radius of celestial bodies
After the explosion, the team turned to other Keck instruments to continue observing. Data from the Deep Imaging and Multi-Object Spectrometer (DEIMOS) and the Near-Infrared Echelon Spectrometer (NIRES) show that the precursor star has 10 times the mass of the Sun. The star is located in the NGC 5731 galaxy, about 120 million light-years away.
The team's observations give some new insight into type II supernovae and their predecessors. Before these observations, no one had seen a red supergiant exhibit such a peak in brightness and such a powerful eruption before it exploded. It is generally assumed that they should be relatively calm in their final days.
Red supergiants spew out material before the core collapses. But the timescale for this material to eject is much longer than SN 2020tlf. The supernova emits ring stellar material (CSM) for 130 days before collapse, which makes it a bit confusing. The bright flashes of light before the star's explosion were somehow related to the ejected ring stellar material, but the research team wasn't sure how they interacted.
The artist's impression of the explosion of a type II supernova, the destruction of a huge supergiant.
The remarkable variability of the star's interior that causes collapse is puzzling. The star's intense light burst before its explosion indicated that something unknown had happened in its internal structure. Whatever these changes are, they cause huge jets of gas before the star collapses and explodes.
In their paper, the authors discuss the causes that can cause gas jets. One possibility is a wave-driven loss of mass, which occurs in the late stages of stellar evolution. "In the last years before SN was able to inject energy into the outer stellar layer, the combustion of oxygen or neon stimulated gravitational waves, causing the surface to expand and explode with mass loss," they wrote. "But the current wave-driven model doesn't match the gas jets of the predecessor star." They coincide with the radius of the last 130 days of the previous star, but are inconsistent with the luminosity burst.
In the conclusion of the paper, the authors make a brief summary: "Given the range of prestellar mass derived from the nebula spectrum, the mass loss, and the enhancement of precursor star radiation, it is likely that it is the result of deep instability inside the star, most likely related to the final stage of nuclear combustion." Both gravitational waves produced during the neon/oxygen combustion phase and energy deposits generated in the last 130 days of silicon flashes of the former star can eject stellar material that can then be detected in pre-explosion fluxes and early SN spectra. ”
If there's one supernova that behaves like that, there's definitely more. The team's findings mean that short-lived investigations like the Young Supernova Experiment now have a way to find more supernovae in the future. If the investigation finds more stars spewing out material like this, then they know to pay close attention to it to see if it collapses and explodes.
"I'm very excited about all the new 'unknowns' that this discovery has unlocked," Jacobson-Galán said. "Detecting more events like SN 2020tlf will greatly influence how we define the final months of stellar evolution, connecting observers and theorists to seek to solve the puzzle of how massive stars spend their final moments of life."
original:
https://www.universetoday.com/153993/astronomers-watch-a-star-die-and-then-explode-as-a-supernova/