Supernova Refsdal with galaxy cluster
NASA, ESA, S. Rodney, FrontierSN Team, T. Troy, P. Kelly, GLASS Team, J. Lotz, Frontier Fields Team, M. Postman, CLASH Team, Z. Levay
Distant supernovae discovered by the strange properties of gravitational lensing have been used to measure the expansion of the universe. The result is an unexpected twist to the tension that has lasted for years.
Gravitational lensing occurs when light from a distant object is bent and distorted by the gravity of a relatively nearby, massive object. This can cause several images of distant objects to appear around nearby objects, similar to the pattern you see when looking through a distorted lens such as the bottom of a water glass. Because light from background objects takes different paths to form each image, they can appear in front of us at different times.
Patrick Kelly Doctors at the University of Minnesota used this strange effect to calculate the Hubble constant, a measure of the expansion rate of the universe. They did this using light from the supernova Lefsdahl, which is gravitationally lensed by a nearby cluster of galaxies. The supernova was first discovered in 2014, and new images of the supernova were released in 2015, allowing researchers to use the time delay between images to calculate how fast the expansion of the universe will carry the supernova away from Earth. Now
There are two main ways to measure the Hubble constant. The first, called a cosmic distance ladder, uses measurements of relatively nearby objects to determine how fast those objects are moving away from Earth. The second uses observations of the cosmic microwave background (CMB), a remnant light from the Big Bang, so measurements must be extrapolated in time using cosmologists’ best models of the universe. there is.
The two methods have disagreed for decades on the so-called Hubble tension. The Hubble constant for the distance ladder is 73 kilometers per second per megaparsec (km/s/mpc), while the value for the CMB method is about 67 km. /sec/mpc. Researchers have long hoped that an independent method could help resolve this tension, but have yet to succeed. This new measurement using the supernova Refsdal gives a value of about 67 km/s/mpc, consistent with the CMB method, although it is based on observations of individual objects as well as the distance ladder method. .
The new results do not rule out higher values, but they do mean that the models used to study gravitationally lensed objects are out of balance. “If the value of the Hubble constant turns out to be 73, as local measurements to date suggest, there must be something wrong with our understanding of cluster lenses. are routinely used to study the universe,” says Kelly.
The researchers are now tracking other lensed supernovae to see if they can get more measurements using this method, and other teams will measure the Hubble constant as well. I am passionate about another independent method. If we can’t find a way to match the measurements to each other, we may need entirely new and unusual physics models to explain what’s really going on.
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