Gravitationally Lensed Supernovas SN Ares and SN Athena Offer New Insights into Universe's Expansion

Astronomers have identified two gravitationally lensed supernovas, SN Ares and SN Athena, which are expected to provide insights into the universe's expansion rate. These supernovas erupted billions of years ago, with their light split into multiple images by gravitational lensing, each traveling a different path to Earth.

Researchers anticipate future observations of these delayed images to offer precise constraints on cosmological expansion.

Discovery and Gravitational Lensing

Conor Larison, a postdoctoral researcher at the Space Telescope Science Institute, presented the discovery at the 247th meeting of the American Astronomical Society. The observations are initial results from the Vast Exploration for Nascent, Unexplored Sources (VENUS) treasury program, which utilizes the James Webb Space Telescope (JWST) to survey 60 dense galaxy clusters acting as cosmic lenses.

This phenomenon, where massive celestial objects bend light from distant sources, was predicted by Albert Einstein's theory of relativity. Seiji Fujimoto, principal investigator of the VENUS program, noted that the program is designed to identify rare events in the distant universe.

SN Ares and SN Athena

SN Ares, the first lensed supernova discovered by VENUS, exploded nearly 10 billion years ago. A foreground galaxy cluster, MJ0308, has split its light into three images. One image has already reached telescopes, but the other two are predicted to arrive in approximately 60 years due to gravitational time dilation near the cluster's center.

This extended delay could allow for an experiment to constrain cosmological evolution with high precision.

A delayed image of SN Athena, which erupted when the universe was about half its current age, is expected within the next one to two years. Its observation will test the accuracy of current predictive models for lensed supernova arrivals.

Addressing the Hubble Tension

The predicted reappearance times of these supernovas, when compared with their actual arrival, will provide measurements for the Hubble constant, which describes the universe's expansion rate. Currently, different measurement methods for the Hubble constant yield conflicting values, a disparity known as the Hubble tension. Calculations based on the cosmic microwave background suggest an expansion rate of 67 kilometers per second per megaparsec, while those using Cepheid stars indicate 73 kilometers per second per megaparsec.

According to Larison, measuring the time delays from these lensed supernovas offers an independent method to gauge the universe's evolution and could help reconcile the Hubble tension.

This approach provides a measurement of the physical scale of the lensing system, which is directly dependent on cosmic evolution.

Advances in Observation

The use of lensed supernovas to study the universe's expansion was first formally suggested 60 years ago. Before the VENUS program, fewer than 10 such supernovas had been identified. Since VENUS began in July, eight new lensed supernovas have been discovered, almost doubling the known sample.

This acceleration in discovery is attributed to the depth and wavelength coverage capabilities of JWST.

Lensed supernovas are considered significant prospects for long-baseline cosmology, which studies the universe's changes over its 13.8 billion-year existence. The long-term implications for the universe's expansion, including the potential weakening of dark energy, remain subjects of ongoing research.