Researchers using NASA’s James Webb Space Telescope have discovered a rare supernova that is helping to better measure the expansion rate of the universe, known as the Hubble constant.
This new discovery adds valuable insights to previous findings from NASA’s Hubble Space Telescope, confirming earlier measurements.
The supernova, nicknamed SN H0pe, was discovered by Brenda Frye from the University of Arizona and her team.
They found three points of light while observing a distant cluster of galaxies. These points weren’t visible in earlier images taken by the Hubble Telescope in 2015 but appeared in the recent data from Webb.
The team realized they were seeing a Type Ia supernova, an explosion of a white dwarf star.
This type of supernova is useful for measuring distances because it has a known brightness, making it a “standard candle” for calculations.
What makes this discovery even more interesting is that the supernova is gravitationally lensed. Gravitational lensing occurs when a large cluster of galaxies bends and magnifies the light from objects behind it.
In this case, the cluster bent the light from SN H0pe, splitting it into three separate images, similar to how a trifold mirror shows three reflections of a person. The middle image was flipped compared to the other two, a predicted effect of lensing.
Since light takes different paths due to lensing, it reaches Earth at different times.
This allowed scientists to observe the supernova at three different moments in its explosion, giving them valuable information to calculate the Hubble constant, which measures how fast the universe is expanding.
The discovery of SN H0pe was followed by a series of studies using telescopes in Arizona, including the MMT and Large Binocular Telescope, to confirm the supernova’s distance and age.
They determined that SN H0pe is one of the most distant Type Ia supernovae ever observed, occurring about 3.5 billion years after the big bang.
The team also used seven different models to analyze how the galaxy cluster affected the supernova’s light.
These models helped refine the measurements, and the final value for the Hubble constant was calculated to be 75.4 kilometers per second per megaparsec (with a margin of error of +8.1/-5.5). This means that for every million parsecs (about 3.26 million light-years), the universe is expanding by 75.4 kilometers per second.
This new value matches other measurements from nearby parts of the universe but is slightly different from measurements taken from when the universe was much younger, creating some debate among scientists. Future observations will help improve the precision of this value, leading to a better understanding of how our universe is expanding.
