For decades, scientists have disagreed about a fundamental question: how quickly is the Universe expanding' But this year, astronomer Wendy Freedman announced results that could help to put the controversy to rest. The long-standing puzzle has been that two methods to measure the cosmic expansion rate, known as the Hubble constant, give stubbornly different answers. Studies using fluctuations in the cosmic microwave background ' the afterglow of the Big Bang ' suggest that for every megaparsec (Mpc; or 3.2 million light years) farther out one looks, galaxies rush away 67 kilometres per second faster. But when scientists, including Freedman, measured the recession rate of far galaxies and estimated their distance, they got a larger Hubble constant: variously 72'74 km s'1 Mpc'1. The method for estimating the distance of galaxies is crucial. It relies on observing the brightness of supernovae (exploding stars) in those galaxies. To calibrate how a supernova's apparent brightness relates to its distance, researchers rely on comparisons to 'standard candles': well-studied stars found relatively nearby, in the Milky Way's cosmic neighbourhood....

Troy Van Voorhis, the Robert T. Haslam and Bradley Dewey Professor of Chemistry, will step down as department head of the Department of Chemistry at the end of this academic year. Van Voorhis has served as department head since 2019, previously serving the department as associate department head since 2015. 'Troy has been an invaluable partner and sounding board who could always be counted on for a wonderful mix of wisdom and pragmatism,' says Nergis Mavalvala, the Kathleen and Curtis Marble professor of astrophysics and dean of the MIT School of Science. 'While department head, Troy provided calm guidance during the Covid pandemic, encouraging and financially supporting additional programs to improve his community's quality of life.' 'I have had the pleasure of serving as head of our department for the past five-plus years. It has been a period of significant upheaval in our world,' says Van Voorhis. 'Throughout it all, one of my consistent joys has been the privilege of working within the chemistry department and across the wider MIT community on research, education, and community building.'...

The MIT Kavli Institute for Astrophysics and Space Research (MKI) is a project lead for one of two finalist missions recently selected for NASA's new Probe Explorers program. Working with collaborators at the University of Maryland and Goddard Space Flight Research Center, the team will produce a one-year concept study to launch the Advanced X-ray Imaging Satellite (AXIS) in 2032. Erin Kara, associate professor of physics and astrophysicist at MIT, is the deputy principal investigator for AXIS. The MIT team includes MKI scientists Eric Miller, Mark Bautz, Catherine Grant, Michael McDonald, and Kevin Burdge. Says Kara, "I am honored to be working with this amazing team in ushering in a new era for X-ray astronomy." The AXIS mission is designed to revolutionize the view scientists have of high-energy events and environments in the universe using new technologies capable of seeing even deeper into space and further back in time. "If selected to move forward," explains Kara, "AXIS will answer some of the biggest mysteries in modern astrophysics, from the formation of supermassive black holes to the progenitors of the most energetic and explosive events in the universe to the effects of stars on exoplanets. Simply put, it's the next-generation observatory we need to transform our understanding of the universe."...

A new study by MIT physicists proposes that a mysterious force known as early dark energy could solve two of the biggest puzzles in cosmology and fill in some major gaps in our understanding of how the early universe evolved. One puzzle in question is the 'Hubble tension,' which refers to a mismatch in measurements of how fast the universe is expanding. The other involves observations of numerous early, bright galaxies that existed at a time when the early universe should have been much less populated. Now, the MIT team has found that both puzzles could be resolved if the early universe had one extra, fleeting ingredient: early dark energy. Dark energy is an unknown form of energy that physicists suspect is driving the expansion of the universe today. Early dark energy is a similar, hypothetical phenomenon that may have made only a brief appearance, influencing the expansion of the universe in its first moments before disappearing entirely. Some physicists have suspected that early dark energy could be the key to solving the Hubble tension, as the mysterious force could accelerate the early expansion of the universe by an amount that would resolve the measurement mismatch....