NASA’s James Webb Space Telescope’s Near-Infrared Camera (NIRCam) image of the PLCK galaxy cluster G165.7+67.0, also known as G165, shows at left the magnifying effect that a cluster foreground can have on the distant universe beyond. The cluster in the foreground is 3.6 billion light years from Earth. The enlarged region on the right shows the triple-imaged H0pe supernova (labeled by white dotted circles) due to gravitational lensing. In this image, blue represents light at 0.9, 1.15 and 1.5 microns (F090W + F115W + F150W), green represents 2.0 and 2.77 microns (F200W + F277W), and red represents 3.56, 4.1 and 4.44 microns (F356W + F410M + F444W). ). Credits: NASA, ESA, CSA, STScI, B. Frye (University of Arizona), R. Windhorst (Arizona State University), S. Cohen (Arizona State University), J. D’Silva (University of Western Australia, Perth), A. Koekemoer (Space Telescope Science Institute), J. Summers (Arizona State University).
Measuring the Hubble constant, the rate at which the universe is expanding, is an active area of research among astronomers around the world who analyze data from ground-based and space-based observatories. NASA’s James Webb Space Telescope has already contributed to this ongoing discussion. Earlier this year, astronomers used Webb data containing Cepheid variables and Type Ia supernovae, reliable distance markers for measuring the rate of expansion of the universe, to confirm previous measurements by the Hubble Space Telescope from NASA.
Today, researchers are using an independent measurement method to further improve the accuracy of the Hubble constant: gravitationally lensed supernovae. Brenda Frye of the University of Arizona, along with a team consisting of many researchers from different institutions around the world, is leading this effort after Webb’s discovery of three points of light in the direction of a distant, densely populated galaxy cluster. The Space Telescope Science Institute recently invited Dr. Frye to tell us more about what the team has dubbed Supernova H0pe and how gravitational lensing effects provide insight into the Hubble constant.
“It all started with a question from the team: ‘What are these three points that didn’t exist before? Could this be a supernova?'” she said. “The points of light, not visible in Hubble imaging of the same cluster in 2015, were evident when images of PLCK G165.7+67.0 arrived at Earth from Webb’s guaranteed-time observations of the main extragalactic zones for the Reionization and Lens Science (PEARLS). The team notes that the question came to mind first for good reason: “The G165 field was selected for this program because of its high rate of star formation of over 300 solar masses per year, an attribute that correlates with higher supernova rates.
“The first analyzes confirmed that these points corresponded to an explosive star, with rare qualities. Firstly, it is a type Ia supernova, explosion of a white dwarf star. This type of supernova is generally called “candle standard”, meaning that the supernova had a known intrinsic luminosity. Second, it is subject to gravitational lensing.
“Gravitational lensing is important in this experiment. The lens, made from a galaxy cluster between the supernova and us, bends the supernova’s light into multiple images. This is similar to the way a three-way vanity mirror panes presents three different images of a person sitting in front. In Webb’s image, this was demonstrated right before our eyes in that the middle image was inverted relative to the other two images, a “lensing” effect. » predicted by theory.
“To obtain three images, the light traveled three different paths. Because each path had a different length and the light moved at the same speed, the supernova was photographed in this Webb observation at three different times during its explosion In the triple mirror By analogy, a delay ensued in which the right mirror showed a person lifting a comb, the left mirror showed hair being combed, and the middle mirror showed the person posing. the comb.
“Supernova triple images are special: the delays, distance from the supernova and gravitational lensing properties give a value for the Hubble constant or H0 (pronounced H-naught). The supernova was named SN H0pe because it gives to astronomers the hope of better understanding the universe change in expansion rate.
“In an effort to explore SN H0pe in more depth, the PEARLS-Clusters team drafted a Director Webb Discretionary Time (DDT) proposal that was evaluated by scientific experts in a doubly anonymous review and recommended by the Webb Science Policy Group for DDT observations. At the same time, data were acquired at the MMT, a 6.5-meter telescope on Mount Hopkins, and the Large Binocular Telescope on Mount Graham, both in Arizona. By analyzing the two observations, our team was able to confirm that SN H0pe is anchored on Mt. A background galaxy, well behind the cluster, which existed 3.5 billion years after the big bang.
“SN H0pe is one of the most distant Type Ia supernovae observed to date. Another team member made another delay measurement by analyzing the evolution of its scattered light in its constituent colors or “spectrum ” by Webb, confirming the type Ia nature of SN Espoir.
“Seven subgroups contributed lens models describing the 2D matter distribution of the galaxy cluster. Since the Type Ia supernova is a standard candle, each lens model was “ranked” based on its ability to predict the delays and luminosity of the supernova compared to the true measured values.
“To avoid bias, the results were masked by these independent groups and revealed to each other on the announced day and time of a ‘live unblinding.'” The team reports that the value of the Hubble constant is 75.4 kilometers per second per megaparsec, plus 8.1 or minus 5.5 (One parsec is 3.26 light years of distance.) This is only the second measurement of the constant of Hubble by this method, and for the first time using a standard candle The principal investigator of the PEARLS program remarked: “This is one of Webb’s great discoveries and it leads to a better understanding of this parameter. fundamental to our universe.”
“Our team’s results are impactful: the value of the Hubble constant matches other measurements in the local universe and is somewhat in tension with values obtained when the universe was young. Webb’s observations at cycle 3 will improve the uncertainties, thus allowing more sensitive constraints on H0”.
Provided by the Space Telescope Science Institute
Quote: Webb researchers discover lensed supernova and confirm Hubble strain (October 1, 2024) retrieved October 1, 2024 from
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