How fast is the universe expanding? Scientists use rare events to make calculations

Astronomers are on the verge of making great strides in understanding one of the universe’s most profound mysteries: the rate at which the universe is expanding.

With NASA’s Nancy Grace Roman Space Telescope scheduled to launch by May 2027, scientists are preparing to take a new approach to solving this mystery.

The Rome Space Telescope will provide an unprecedented panoramic view of the universe, capturing wide-ranging images for the careful search for supernovae through gravitational lensing.

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These rare cosmic events are key to measuring the universe’s expansion rate, known as the Hubble constant. However, this constant has been the subject of debate due to discrepancies in values ​​obtained from different measurement techniques, a phenomenon known as the “Hubble tension.”

Roman’s mission is to investigate the mysterious dark energy that affects the expansion of the universe over time. One of his main methods is to measure distances by comparing the intrinsic brightness of type Ia supernovae with the observed brightness.

In contrast, Roman also focuses on gravitational lensing supernovae, offering a unique approach based on geometry rather than brightness.

Lou Strollger of the Space Telescope Science Institute (STScI), co-leader of the team preparing Roman’s study of these objects, expressed enthusiasm about the telescope’s capabilities. “Roman is an ideal tool to begin studying gravitational lensing supernovae,” he said.

The telescope’s vast field of view and high-resolution imaging greatly increases the chances of detecting these elusive phenomena.

To date, only eight gravitational lensing supernovae have been discovered using observatories such as the Hubble Space Telescope and the James Webb Space Telescope. Of these, only two are suitable for measuring the Hubble constant.

Gravitational lensing occurs when a massive object, such as a galaxy or galaxy cluster, bends the light from a distant star exploding, creating multiple delayed images of the supernova as seen from Earth.

Measuring the time difference between these images provides important distance measurements that help constrain the Hubble constant.

Justin Pierel, co-leader of Strolger, emphasized the importance of this new approach, saying, “Investigating these distances in a fundamentally different way than is common means that different measurement techniques differ.” “This could help us understand what led to these results.”

The Rome Space Telescope maps the universe much faster than any previous space telescope, capturing more than 100 times more area in a single image than Hubble.