Webb researchers discover lensed supernova, confirm Hubble tension

Measuring the Hubble constant, the rate of expansion of the universe, is an active area of ​​research among astronomers around the world, who analyze data from both ground-based and space-based observatories. NASA’s James Webb Space Telescope is already contributing to this ongoing discussion. Earlier this year, astronomers used Webb data, including Cepheid variable stars and Type Ia supernovae, reliable distance markers for measuring the rate of expansion of the universe, to confirm previous measurements by NASA’s Hubble Space Telescope. did.

Now, researchers are using a unique measurement method to further improve the accuracy of the Hubble constant (gravitational lensing supernovae). Brenda Fry of the University of Arizona, along with a large team of researchers from different institutions around the world, discovered this after Webb discovered three points of light pointing in the direction of a distant, densely populated galaxy cluster. He is leading the effort. The Space Telescope Science Institute recently invited Dr. Fry to tell us more about what the team has named supernova H0pe and how gravitational lensing provides insight into the Hubble constant.

“It all started with one question from the team: ‘What are those three points that weren’t there before? Are they supernovas?'” she said. “The 2015 Hubble in the same cluster Spots of light not visible in the image were evident when images of PLCK G165.7+67.0 arrived at Earth from the Prime Extragalactic Region Webb Guaranteed Time Observation for Reionization and Lensing Science (PEARLS). There’s a good reason why this question first came to mind for the Cluster program, the researchers say. “The G165 star region was chosen for this program because of its characteristic high star formation rate of more than 300 solar masses per year,” which correlates with higher supernova rates. ”

“Initial analysis confirmed that these dots correspond to exploding stars with rare properties. First, this is a type Ia supernova, an explosion of a white dwarf star. This type of supernova is commonly It is called a “standard candle”. Second, supernovae are known to be gravitational lensed.

“Gravitational lensing is critical to this experiment. The lens, made up of a galaxy cluster located between the supernova and us, bends the supernova’s light into multiple images. This is because the tri-fold vanity mirror It’s like projecting three different images.” In Webb’s image, this is demonstrated before our eyes in that the central image is inverted with respect to the other two. This is the “lensing effect” predicted by theory.

“To achieve the three images, the light traveled along three different paths. Each path was a different length and the light traveled at the same speed, so this Webb observation shows that the supernova Using the analogy of a three-way mirror, there would be a time delay, with the mirror on the right showing a person holding up a comb and the mirror on the left showing hair being combed. The central mirror displayed a person putting on a comb.

“Tri-fold supernova images are special. The time dilation, supernova distance, and gravitational lensing properties give us the value of the Hubble constant, or H0 (pronounced H-naught). To give hope for better understanding, it was named SN H0pe.

“To further investigate SN H0pe, the PEARLS-Clusters team developed a Webb Director’s Discretionary Time (DDT) proposal. This proposal was evaluated in a double anonymous review by scientific experts and It was recommended by the Webb Science Policies Group. In parallel, data was also acquired by MMT, the 6.5-meter telescope at Mount Hopkins in Arizona, and the Large Binocular Telescope at Mount Graham to analyze both observations. , our team was able to confirm that SN H0pe is anchored in a background galaxy well behind the cluster that existed 3.5 billion years after the Big Bang.

“SN H0pe is one of the most distant type Ia supernovae ever observed.” Another team member will analyze the evolution of the light distributed in its constituent colors or ‘spectrums’ from the web. conducted another time-delay measurement to confirm the nature of SN H0pe’s type Ia supernova. SNH0pe.

“Seven subgroups contributed lensing models that describe the 2D matter distribution of galaxy clusters. Because type Ia supernovae are standard candles, each lensing model has They were “graded” by their ability to predict supernova brightness. .

“To prevent bias, results were blinded from these independent groups and made available to each other at the published ‘live unblinding’ date and time. The researchers report a value for the Hubble constant of 75.4 kilometers per second per megaparsec, plus 8.1 or minus 5.5 (one parsec is equivalent to a distance of 3.26 light years). This is only the second measurement of the Hubble constant using this method. , and the principal investigator of the PEARLS program, which used standard candles for the first time, said: “This is one of Webb’s great discoveries, leading to a better understanding of this fundamental parameter of our universe.” ” said.

“Our team’s results are influential: the value of the Hubble constant is consistent with other measurements of the local Universe and is somewhat in tension with values ​​obtained when the Universe was young. Webb Observations of Cycle 3 improves the uncertainty and allows a more sensitive constraint on H0.” ”