The Webb Space Telescope discovered a supernova that updates the Hubble constant - the expansion rate of the universe

The discovery of SN H0pe, a distant supernova that was observed in three replicates using gravitational insolation, allowed researchers to accurately measure the Hubble constant at different times, revealing insights into the expansion rate of the universe

Using the James Webb Space Telescope, astronomers were able to perfect the Hubble constant measurement by studying SN H0pe, a type Ia supernova observed from Earth through gravitational lensing. This approach, which combines gravitational damping and time-lapse observations, offers a more precise determination of the expansion rate of the universe, and helps reconcile some differences between previous measurements.

Measuring the Hubble constant, which defines the rate of expansion of the universe, is a dynamic area of ​​research for astronomers around the world. These researchers analyze data from ground-based observatories and space telescopes. NASA's James Webb Space Telescope has already made significant contributions to this debate. Earlier this year, astronomers used Webb data that included Cepheid variables and Type Ia supernovae—both reliable cosmic distance markers—to validate previous measurements of the universe's expansion rate made by the telescope. the mourning space

Through gravitational sintering, researchers use an independent measurement method to further improve the accuracy of the Hubble constant - gravitationally lensed supernovae. Brenda Frey of the University of Arizona, and a team of many researchers from various institutions around the world, are leading this effort after discovering three points of light toward a distant and densely populated galaxy cluster. We invite Dr. Frey to tell us more about what the team called the H0pe supernova and how gravitational dusting effects provide insights into the Hubble constant:

"It all started with one question from the team: 'What are these three points that weren't there before? Could this be a supernova?' The bright spots, which were not seen in the Hubble telescope's 2015 image, were evident when images of PLCK G165.7+67.0 reached Earth from the Webb Clusters for Primary Extragalactic Regions of Ionization and Lensing (PEARLS) program points out that the question was the first that jumped to mind for a good reason: 'The field of G165 was chosen for this program due to the rate of star formation higher than 300 solar masses per year, a feature that correlates with higher supernova rates.'"

NASA's James Webb Space Telescope shows a NIRCam (Near Infrared Camera) image of the galaxy cluster PLCK G165.7+67.0, also known as G165, left, showing the magnifying effect a foreground cluster can have on the Universe the far beyond. The magnified area on the right shows the triple imaged H0pe supernova (indicated by white dashed circles) due to gravitational dusting. The lens, which consists of a cluster of galaxies located between the supernova and us, bends the light of the supernova into several images. To obtain three images, the light travels along three different paths. Because each path had a different length, and light traveled at the same speed, the supernova was captured in this Webb observation at three different times during its explosion. The double image supernova offers astronomers a unique way to calculate a new value for Hubble's constant - the rate at which the universe is expanding.

Preliminary analyzes confirmed that these points corresponded to an exploding star, a star with rare properties. First, it is a type Ia supernova, the explosion of a white dwarf star. This type of supernova is usually called a "standard candle", meaning the supernova had a known intrinsic luminosity. Second, it appears to our eyes through a gravitational lens.

The importance of gravity recycling

The lens, which consists of a cluster of galaxies located between the supernova and us, bends the supernova's light into several images. This is similar to how a three-way vanity mirror shows three different images of a person sitting in front of it. In Webb's image this was demonstrated right in front of our eyes in that the middle image was flipped relative to the other two images, a 'clutter' effect predicted by the theory.

To obtain three images, the light travels along three different paths. Because each path had a different length, and light traveled at the same speed, the supernova was captured in this Webb observation at three different times during its explosion. In the triple mirror analogy a time delay was created where the right mirror showed a person picking up a comb, the left mirror showed combed hair and the middle mirror showed the person putting the comb down.

Supernova in different stages of explosion

Triple supernova images are special: the time delays, the distance of the supernova, and the properties of the gravitational cooling yield a value for Hubble's constant or H0 (pronounced H-naught). The supernova was named SN H0pe because it gives astronomers hope of better understanding the changing rate of expansion of the universe.

In an effort to study SN H0pe further, the Pearl Clusters team wrote a James Webb Telescope Director's Discretionary Time (DDT) proposal that was evaluated by science experts in an anonymous double review and recommended by the Webb Science Policy Group for DDT observations. At the same time, data were acquired at the Cluster Metal Telescope (MMT), a 6.5-meter diameter telescope on Mount Hopkins, and the Large Binocular Telescope on Mount Graham, both in Arizona. Analyzing both observations, the team was able to confirm that SN H0pe is anchored to a background galaxy, far behind the cluster, that existed 3.5 billion years after the Big Bang.

SN H0pe is one of the most distant Type Ia supernovae observed so far. Another team member made an additional time delay measurement by analyzing the evolution of its scattered light into its constituent colors or Webb 'spectrum', which confirmed the Type Ia nature of SN H0pe. Seven subgroups contributed lensing models that describe the two-dimensional material distribution of the galaxy cluster. Since the Type Ia supernova is a standard candle, each lens model is 'rated' by its ability to predict the time delays and brightness of the supernova relative to the actual measured values. To avoid bias, the results were blinded from these independent groups and revealed to each other on the announced day and time of 'life without blinding'.

Measurement of the Hubble constant

The team reports the value of Hubble's constant as 75.4 kilometers per second per megafarsec, with a deviation of 8.1 upwards or 5.5 downwards. [One farsec is equivalent to a distance of 3.26 light years.] This is only the second measurement of Hubble's constant using this method, and the first time using a standard candle. The principal investigator of the PEARLS program said, 'This is one of Webb's great discoveries, and it leads to a better understanding of this fundamental parameter of our universe.'"

The conclusions of the study are that the Hubble constant value is consistent with other measurements in the local universe, and is in some tension with values ​​obtained when the universe was young. Additional Webb observations may reduce this uncertainty."

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