As in 2019, the 2011 Nobel Prize in Physics has also been spent on astrophysics. The main contribution of the three scientists who won the prize at the time was to discover the accelerated expansion of the universe by observing the “standard candlelight” Ia supernova in the universe. Why does the universe accelerate rather than expand at a constant speed? Many scholars believe that there is an energy that we have not yet observed to “push” the universe to expand at an accelerated rate, which they call dark energy.
Discovered in 2005, Supernova 2005ke is an Ia supernova. Its dazzling light is an important “standard candlelight” used by astronomers to measure the distance of the universe.
Intern Reporter Yu Ziyue
Therefore, to some extent, the study of supernovae indirectly supports the theory of dark energy.
However, a recent study suggests that we may need to re-examine the relationship between supernovae, accelerated expansion of the universe, and dark energy. A team led by Yonsei University in South Korea conducted a large-scale “survey” of Ia supernovae and found that the absolute brightness of supernovae was significantly related to the age of the star cluster. This means that, in many previous studies, the brightness of type Ia supernovae may not be “standard” as a former “standard candlelight”, meaning that researchers need to correct observations based on the age of the star cluster in which the supernova is located.
How did supernovae prove that the universe is expanding at an accelerated rate? What new research has refreshed people’s perceptions of supernovae? Will it shake the building of the dark energy theory?
Ia Supernova: “Big Brother” measures the accelerated expansion of the universe
“The Ia supernova has a relatively stable luminosity, and the object is so bright that we can see it at a very far distance, so it measures the universe as a ‘standard candlelight’. Zhang Tianmeng, an associate researcher at the National Observatory of the Chinese Academy of Sciences, told Science and Technology Daily.
Supernovae stem from a dramatic explosion experienced by some stars in the universe as they evolved near the end. The eruptions of this life are so intense that the electromagnetic radiation that is produced often illuminates the entire galaxy in which it is located. As an important subcategory of supernovae, ia supernovae have a special place in cosmology and have been listed as one of the main objects of stellar research in the Last Decade in the New Millennium Astronomy and Astrophysics.
Zhang Tianmeng introduced that the Type Ia supernova comes from the outbreak of white dwarf shimirising in the binary system. White dwarfs can obtain the material of their companion stars through accretion and other means, and when their mass accumulates to about 1.4 solar masses, the internal free electrons are pressed against the gravitational potential energy, and the white dwarf collapses inward, creating a supernova explosion. Since the energy of the Ia supernova explosion comes mainly from the isotope decay of nickel with an atomic weight of 56, and the mass of nickel 56 mainly depends on the total mass of the white dwarf, it can be considered that the Ia supernova has a relatively stable luminosity.
It is not difficult to imagine that the Ia supernova near us will look brighter, and the distance will look relatively darker, that is, the Ia supernova’s visual brightness and distance have a strict correspondence. In this way, we can infer how far it is from us based on the observed ia supernova’s visual brightness and its changes.
Of course, the universe is expanding, and there is also the problem of redshifting, where the wavelength of light is elongated and offset to red light with a longer wavelength. Thus, the distance away from objects provided by redshift data could help scientists better understand the state of the universe’s expansion.
The 2011 Nobel Prize winner in physics used the above principles to spy on the “sky machine”. “They found that the light of the Type Ia supernova, farther away, was darker than predicted by the uniformized cosmic model, and concluded that it may have been the presence of dark matter that caused the universe to accelerate rather than expand at a constant speed. Zhang Tianmeng said.
In Zhang Tianmeng’s view, although in recent years, many researchers want to use gamma storm, quasar and gravitational waves as the new standard candlelight to measure the universe, but limited by uniformity, number of discoveries, observation difficulty and other reasons, but also can not completely replace the Ia supernova.
New study: Brightness evolution is linked to galaxy age
Now, a new study from Yonsei University in South Korea raises questions about the evolution of the brightness of type Ia supernovae in the past.
They believe that the brightness of the Type Ia supernova may not be as simple as previously thought, but rather to the shape, mass, and local rate of star formation of the supernova, which may be related to the population nature of the star.
To understand the origins of these correlations, the researchers made a large-scale spectral observation of the Type Ia supernova. They found that when the luminosity of the Type Ia supernova was standardized, there was a significant correlation between the age of the star population and the confidence level of 99.5 percent. The findings will be published soon in the astrophysical journal.
“This is by far the most direct and rigorous test of the evolution of the Ia super-new starlight. “The most immediate and powerful evidence of the existence of dark energy comes from the measurement of galaxy distance by ia supernovae, and this conclusion is based on the premise that the corrected Ia supernova brightness obtained through empirical standardization does not change with distance,” the summary said. But based on the findings, the researchers believe that supernova cosmology must carefully consider this systemic bias before studying the details of dark energy.
So, has anyone ever been equally concerned about the brightness evolution of ia supernovae? The answer is yes.
“There have been many studies that have found that the luminosity of ia supernovae is related to their environment, including the type of galaxy in which they are located, its mass, and star formation rate. The methods and models used by different researchers differ widely, with similar conclusions to Korean university researchers, but the opposite, or even irrelevant. Zhang Tianmeng dao.
As for why the findings differ widely, mainly because the luminosity of the Type Ia supernova is not completely uniform. Zhang Tianmeng introduced that there are many factors affecting the luminosity, including the metal abundance, rotation, companion nature and extinction of its predecessor star, coupled with the difficulty of supernova observation and the difference between equipment, will make the measurement error increase, the results have a greater impact. There may also be a degree of coupling between these factors, which causes each other to interfere with each other when correcting the super-new starlight, affecting the result of correction.
“In fact, these conclusions are based on large sample sprees of Ia supernovae in near-neighbor galaxies, and use them in a single high-red shift galaxy and type Ia supernova, with a large degree of deviation.” Zhang Tianmeng said that in the next few years, many large field of view of the sky tour plan will be carried out one after another, such as the use of the United States wide-field space reflector telescope and China’s space telescope, will find and accurately measure more high-red moving Ia supernova, from which to pick out more pure “standard candlelight”, so that the measurement of the cosmic parameters will be more reliable.
Dark Energy “Guardians”: Supernova is not the only one
Modern cosmology studies have shown that the universe is mainly composed of conventional matter, dark matter, dark energy. Of these, dark energy is more than 70%, the largest component of the universe. Although there are many theories in the academic world that try to explain dark energy, it is still not clear exactly what it takes.
It is precisely because of the mystery of dark energy that many people wonder if the conclusions of this new study are further confirmed, it means that dark energy no longer exists. Will the history of the universe be rewritten?
In Zhang Tianmeng’s view, the Ia supernova is not the only evidence of the theory of accelerated expansion of the universe, dark energy, microwave background radiation and the effects of the resonal sonic shock, and other means also confirmed these conclusions to some extent.
Cai Yifu, a professor in the Department of Astronomy at the School of Physics at the University of Science and Technology of China, made the same point.
Chua said that the cosmic microwave background radiation and the supernova sound wave oscillations, like supernovae, can serve as a yardstick for cosmic ranging, they all have a specific relationship that confirms the redshift and distance of the universe, but each individual range is uncertain, and they measure the universe at different times. For example, microwave background radiation measures the universe 380,000 years after the creation of the universe, the resonal sound wave shock can be measured billions of years or even 10 billion years ago of the universe, supernova measures in the last few billion years of the state of the universe.
As can be seen, scholars can’t be accurate to the exact time of the evolution of the universe, but rather have a hundred-million-year error.
“So it’s hard for any observation altogether to tell a story about what’s going on in the universe alone, but it’s like a jigsaw puzzle, and we put a lot of evidence together to piece together the truth about what happened in the universe for nearly 13.8 billion years.” Tsai said.