Astronomers are on the brink of a significant breakthrough in understanding one of the universe’s most profound mysteries — the rate at which it is expanding.
With the anticipated launch of Nasa’s Nancy Grace Roman Space Telescope by May 2027, scientists are preparing to embark on a new approach to unravel this enigma.
The Roman Space Telescope will provide an unprecedented panoramic view of the cosmos, capturing wide swaths of images that will be meticulously searched for gravitationally lensed supernovae.
These rare cosmic events are key to measuring the universe’s expansion rate, known as the Hubble constant. However, this constant has been a subject of debate due to discrepancies in values obtained from different measurement techniques — a phenomenon referred to as the “Hubble tension.”
Roman’s mission will delve into the mysterious dark energy that influences the universe’s expansion over time. One of the primary methods involves comparing the intrinsic brightness of type Ia supernovae with their observed brightness to gauge distances.
In contrast, Roman will also focus on gravitationally lensed supernovae, offering a unique geometric-based method rather than relying on brightness.
Lou Strolger of the Space Telescope Science Institute (STScI) and co-lead of the team preparing for Roman’s study of these objects, expressed enthusiasm about the telescope’s capabilities. “Roman is the ideal tool to let the study of gravitationally lensed supernovae take off,” he said.
The telescope’s vast field of view and high-resolution imaging will significantly increase the chances of detecting these elusive phenomena.
To date, only eight gravitationally lensed supernovae have been discovered using observatories like the Hubble Space Telescope and the James Webb Space Telescope. Of these, just two have been 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 stellar explosion, creating multiple delayed images of the supernova as seen from Earth.
Measuring the time differences between these images can provide critical distance measurements that help constrain the Hubble constant.
Justin Pierel, Strolger’s co-lead, highlighted the importance of this new approach: “Probing these distances in a fundamentally different way than more common methods can help shed light on why various measurement techniques have yielded different results.”
The Roman Space Telescope will map the universe much faster than its predecessors, with the ability to capture over 100 times the area of Hubble in a single image.
Shambhu Kumar is a science communicator, making complex scientific topics accessible to all. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
