Supernova H0pe could solve a mystery of the universe


A rare supernova, named H0pe, appearing distorted three times in a single image, could help researchers solve a long-standing mystery of the universe. The Type 1a supernova was first discovered in photographs captured by NASA‘s James Webb Space Telescope (JWST).

In these images (ref.), the exploding star can be seen as an arc of orange light with three bright points surrounding part of the galaxy cluster PLCK G165.7+67.0 (G165), which is approximately 4.5 billion light-years away from Earth.

Gravitational Lensing

The arc of light is the result of gravitational lensing. This effect occurs when light from a distant object passes through the space-time warped by the gravity of a massive foreground object positioned between the distant object and the observer. Gravitational lensing magnifies the images, making it easier for researchers to analyze.

The three bright points in the arc around G165 appear to be three separate light sources distorted by the foreground galaxy. However, in reality, the supernova, which is located about 16 billion light-years away from us, has been duplicated twice by the lensing effect. Astrophysicist and science communicator Ethan Siegel, not involved in the study, has stated that H0pe could help resolve a mystery about the universe’s expansion: Hubble tension.

The diagram illustrates how gravitational lensing works. In this example, light from a galaxy travels through the curved space-time surrounding a galaxy cluster.
The diagram illustrates how gravitational lensing works. In this example, light from a galaxy travels through the curved space-time surrounding a galaxy cluster.

Hubble Tension is based on a discrepancy between the two primary methods of estimating the rate of the universe’s expansion, known as the Hubble constant. The first method involves measuring the expansion using cosmic microwave background radiation (CMB), a relic of the Big Bang. The second method involves measuring how specific objects, such as galaxies and supernovae, are moving away from us. This method consistently provides a slightly higher value than the first.

Discrepancy in Calculations

This problem has puzzled scientists for decades. There is no clear reason why one method should yield a different result from the other. The puzzle has even led some researchers to declare a crisis in cosmology.

H0pe could help address the problem because it is a Type 1a supernova, which astronomers call a standard candle. It is an incredibly reliable reference point from which we can measure the universe’s expansion.

Type 1a supernovae involve a white dwarf star stealing material from a binary partner star before reaching critical mass and exploding. These explosions have nearly uniform initial brightness and fade at the same rate over time. By comparing these standard candles at various distances from Earth, scientists can precisely determine how fast they are moving away from us and thus infer the rate of the universe’s expansion.

H0pe as a Standard Candle

“H0pe is a particularly important standard candle because it is the second most distant Type 1a supernova ever detected” Siegel reported. The strong gravitational lensing and duplication in the new images also provide researchers with more data to work with than usual.

The idea of using duplicated supernovae to tackle the Hubble tension problem is not new. In May, scientists used data from a supernova called Refsdal to calculate a new value for the Hubble constant. Although this still differed from the value calculated using CMB, the difference between the two measurements was reduced, suggesting that they could eventually converge.

It is currently unclear whether the supernova H0pe can definitively resolve this age-old mystery of the universe. But researchers are confident that if the keen eye of the JWST can continue to spot more distant standard candles, the Hubble tension problem may finally be resolved.

Stefano Gallotta
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