Cosmologists have found a way to reproduce Health Measuring the distance to a supernova explosion – one of their tried and true tools for studying the mysterious dark energy that is making the universe expand faster and faster. The collaboration with the nearby Supernova Plant (SNfactory), led by Greg Aldring of the Energy Department’s Lawrence Berkeley National Laboratory (Berkeley Laboratory), will enable scientists to study dark energy with dramatically improved accuracy and precision, providing cross-probe distance technology. . far and time. The results will also be at the heart of a large upcoming cosmic experiment that will use new ground and space telescopes to test alternative explanations for dark energy.
Two papers have been published at Journal of Astrophysics Report these findings, with Kyle Boone as lead author. Currently, I am a Postdoctoral Fellow at Washington UniversityBoone is a former Nobel Prize-winning graduate student at Saul Perlmutter, the chief scientist at the Berkeley Laboratory and a UC Berkeley professor who led one of the teams that originally discovered dark energy. Perlmutter was also a co-author on both studies.
Supernovae were used in 1998 to make the surprising discovery that the expansion of the universe is accelerating, not slowing down as expected. This acceleration – attributed to dark energy making up two-thirds of all the energy in the universe – has since been confirmed by various independent technologies as well as more detailed supernova studies.
Dark energy discovery depends on the use of a specific class of supernovae, Type 1. These supernovae always explode at roughly the same intrinsic maximum brightness. Since the maximum brightness of the observed supernova is used to infer the distance, the remaining small differences in the intrinsic maximum brightness limit the accuracy of dark energy that can be tested. Despite 20 years of improvement by many groups, studies of dark energy supernovae have so far been limited by this difference.
The top left image shows the spectrum – brightness versus wavelength – of the two supernovae. One is near and the other is very far. In order to measure dark energy, scientists need to measure the distance between them very precisely, but how do they know if they are the same? The lower right image compares the spectrum – showing that they are actually “twins”. This means that their relative distance can be measured with an accuracy of 3 percent. The bright dot in the top center is an image of the 1994D Hubble Space Telescope (SN1994D) in the galaxy NGC 4526. Credit: Image: Zosia Rostomian / Berkeley Lab; Photo: NASA / European Space Agency
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Double the number of supernovae
The new results announced by SNfactory come from a multi-year study entirely dedicated to improving the accuracy of cosmic measurements made with supernovae. Measuring dark energy requires a comparison of the maximum brightness of a distant supernova, which is billions of light years away from the nearest supernova, “only” 300 million light years away. The team studied hundreds of nearby supernovae in great detail. Each supernova is measured multiple times, with intervals of several days. Examine each supernova spectrometer, noting its intensity over the entire wavelength range of visible light. The instrument specially designed for this investigation, the Supernova Integrated Field Spectrometer, mounted on the University of Hawaii’s 2.2m telescope at Maunakea, was used to measure the spectrum.
“We’ve always had the idea that if the explosion physics of two supernovae were the same, their maximum brightness would be the same. Using a nearby supernova factory spectrum as a type of CT scan during a supernova explosion, we were able to test it. this idea, “said Perlmutter.
In fact, a few years ago, physicist Hanna Fakhoury, then a graduate student working with Perlmutter, found the key to today’s results. Looking at the huge spectrum the SNfactory captures, I find that in a large number of cases the spectra of two different supernovae appear very nearly identical. Of the 50 or so supernovae, some were nearly identical twins. When the oscillating spectrum of a pair of twins is installed, there is only one pathway for the eye. The current analysis relies on these observations to model the behavior of supernovae in periods approaching their maximum brightness time.
This new work nearly doubled the number of supernovae used in the analysis. This left a large enough sample to apply machine learning techniques to identify these twins, leading to the discovery that the spectra of type Ia supernovae differ only in three ways. The intrinsic brightness of a supernova also depends primarily on these three observed differences, making it possible to measure the distance of the supernova with an observed accuracy of about 3%.
Last but not least, the new method is not biased around the previous method, as seen when comparing supernovae found in different types of galaxies. Because near galaxies are somewhat different from distant galaxies, there is serious concern that this dependence could result in misreading of dark energy measurements. This concern can now be greatly reduced by measuring distant supernovae with this new technique.
In explaining this work, Boone notes that “conventional measurements of supernova distance use curves of light – images are captured in several colors as the supernova lights up and disappears. Instead, we used the spectrum from each supernova. It is much more detailed, and with machine learning techniques, it becomes possible to see the complex behaviors that are key to more accurate distance measurements. “
The results of the Bonn paper will inform two major future experiments. The first experiments will be carried out at the 8.4 meter-long Rubin Observatory, which is under construction in Chile, with the Space and Time Heritage Survey, a joint project between the Department of Energy and the National Science Foundation. The second is NASANext is Roman Nancy Grace Telescope. The telescope will measure thousands of supernovae to improve dark energy measurements. They will be able to compare their results with measurements made using complementary techniques.
Aldering, who is also a co-author of the paper, notes, “This technique of measuring distance is not only more accurate, but requires only one spectrum, captured when supernovae are brighter and thus easier to notice – game-changing! of particular value in these areas where preconceptions are found to be flawed and the need for independent verification is high.
SNfactory collaborations include the Berkeley Laboratory, the Laboratory for Nuclear and High Energy Physics at the Sorbonne, the Astronomy Research Center in Lyon, and the Physics Institute for Infinity 2 at Claude Bernard University, Yale UniversityGermany’s Humboldt University, Max Planck Institute for Astrophysics, Tsinghua Chinese University, Center for Particle Physics in Marseille, and Claremont-Auvergne University.
This work was supported by the Department of Energy’s Office of Science, NASA’s Division of Astrophysics, the Gordon and Betty Moore Foundation, the French National Institute of Nuclear and Particle Physics, and the French National Institute for Earth and Astronomy Center for Scientific Research. German Research Foundation, German Space Center, European Research Council, Tsinghua University and the Chinese National Foundation for Natural Sciences.
Example of a supernova: Palomar SN 2011fe Temporary Factory discovered in the Pinwheel galaxy near the Big Dipper on August 24, 2011. Credit: BJ Fulton, Las Cumbres Observatory Global Telescope Network
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Additional background
In 1998, two competing groups studying supernovae, the Supernova Cosmology Project and the Supernova Search Team, announced that they had found evidence that, contrary to expectations, the expansion of the universe was not slowing down but was getting faster and faster. Dark energy is a term used to describe the cause of acceleration. The 2011 Nobel Prize was awarded to leaders of two teams: Saul Perlmutter of Berkeley Lab and UC Berkeley, project leader of Supernova Cosmology, and to Brian Schmidt of Australian National University Adam Rees from Johns Hopkins from the High-z team.
Additional techniques for measuring dark energy include a Department of Energy-supported dark energy spectroscopy tool, led by Berkeley Lab, which will use spectroscopy on 30 million galaxies in a technology called acoustic baryon oscillation. Rubin will also use another lens, which is called a weak gravity lens.
Reference:
“Type 1 supernova inclusion I. Spectral variation in maximum light” by K. Boone, G. Aldering, P. Antilogus, C. Aragon, S. Bailey, C. Baltay, S. Bongard, and C. Buton, Y. Copin , S. Dixon, D. Fouchez, E. Gangler, R. Gupta, B. Hayden, W. Hillebrandt, AG Kim, M. Kowalski, D. Küsters, P.-F. Léget, F. Mondon, J. Nordin, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, KA Ponder, D. Rabinowitz, M. Rigault, D. Rubin, K. Runge, C. Saunders, G Smadja, N. Suzuki, C. Tao, S. Taubenberger, RC Thomas and M. Vincenzi, 6 May 2021, Journal of Astrophysics.
DOI: 10.3847 / 1538-4357 / abec3c
“Type 1 Supernova Twin Inclusion. II. Improving Estimates of Cosmic Distance ”by K. Boon, J. Aldring, B. Antelugus, C. Aragon, S. Bailey, C. Paltai, S. Bongard, C. Botton, Y. Cobain, S. Dickson Fuchs, E. Gangler , R. Gupta, B. Hayden, W. Hillebrandt, AG Kim, M. Kowalski, D. Küsters, P.-F. Léget, F. Mondon, J. Nordin, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, KA Ponder, D. Rabinowitz, M. Rigault, D. Rubin, K. Runge, C. Saunders, G Smadja, N. Suzuki, C. Tao, S. Taubenberger, RC Thomas and M. Vincenzi, 6 May 2021, Journal of Astrophysics.
DOI: 10.3847 / 1538-4357 / abec3b
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