Boldly Going in Astrophysics

Research highlights from Kavli Astrophysics Institutes

Scientists have released a new survey of all the matter in the universe, using data taken by the Dark Energy Survey in Chile (above) and the South Pole Telescope. Photo by Andreas Papadopoulos.

When looking up on a clear night, especially away from the glare of big-city light pollution, the stars can appear so immediate, so . . . right there. Everyone—even children after posing a few questions to their elders—knows that these bright points overhead are far, far away. Those of us curious about the celestial realm might even be able to recite some facts about the distances to certain well-known stars, such as Alpha Centauri (about 4.37 light years) and Sirius (8.6 light years). These astrophiles can also explain that a light year is how far light travels in a year. At the blazing clip of 186,282 miles per second, that equates to a particle of light annually traversing 5.88 trillion miles. Here's where things start to border on the unfathomable in terms of human reckoning. Just crossing the United States, from Atlantic to Pacific, can seem like a long journey, but it's barely 3,000 miles. A reliable car might last you for 200,000 miles or so, over the course of many years, but that total distance still wouldn't even get you to the Moon. It staggers the mind, then, to realize that when peering up at stars, the particles of light from them that pass through our eyeballs and strike our retinas have traveled across trillions upon trillions of miles. The wonders do not just cease there. Because of the vast distances involved and light's finite speed, when we gaze at stars above, we're seeing those stars back in time equivalently to however many light years away they are. Thus, when we appreciatively stare at Sirius, the brightest star, we're seeing Sirius as it appeared more than eight years ago. We're seeing its old-news light that we only receive after it's traveled, oh, 50 trillion miles. We're seeing the 2014 version of Sirius still, here in early 2023. Mind-bending stuff, this astrophysics. It's little surprise, then, that the amazingness of the field attracts so much scientific talent and spurs so much scientific inquiry.

Developing new algorithms to better comprehend the cosmos

The groundbreaking Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) could start as soon as this year. The project will haul in tremendous amounts of data, and gleaning accurate results from the voluminous treasure trove will be a challenge. Helping in this regard is Eli Rykoff, a member of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University. Earlier this year, Rykoff began working as a Rubin calibration scientist on creating special software programs for the project. The algorithms Rykoff and colleagues develop will be needed to convert the raw data the Rubin Observatory captures into useful, usable physical units. Making the data workable in this way will enable researchers to test out major theories, such as the super-robust framework we have for gravity in Einstein's theory of general relativity. A new Research Highlight at KIPAC describes how Rykoff's current work fits into his career of developing astrophysical "apps" for studying gravitational lenses, cosmic distances, and more.

Doubling array's sensitivity could bring "cosmic dawn" into focus

An unprecedented glimpse back to the "cosmic dawn"—the era when the first stars and galaxies began to shine bright—could soon be in the offing. In a recent study, researchers working on an observatory called the Hydrogen Epoch of Reionization Array (HERA) announced that they have successfully doubled the instrument's sensitivity. When fully calibrated and operational, likely later this year, this upgraded HERA could start to gather radio signals from hydrogen gas between 200 million and one billion years post-Big Bang. Researchers hope to form a 3D map using these signals of the pockets of gas that went on to form primordial stars and populated early galaxies. Members of the Massachusetts Institute of Technology's Kavli Institute for Astrophysics and Space Research (MKI) are part of the HERA team.

Weighing up the matter in the universe

Researchers at the Kavli Institute for Cosmological Physics (KICP) at the University of Chicago and colleagues have presented a fresh accounting of the matter in the cosmos. While agreeing well with prevailing theories, the findings do show some divergence by pointing to the universe being less "clumpy" than expected, suggesting revisions may well be in order. The new analysis brought together data from two projects that KICP researchers are involved in, namely the Dark Energy Survey and the South Pole Telescope. The datasets are very different; the former consists of optical observations of million of galaxies captured over a six-year span, and the latter is an ongoing project to capture faint microwave signals comprising the earliest available light in the universe. The contrasting data types served as cross-checks on each other, overall boosting the reliability of the results.

A supermassive black hole gets cut down to size

Detailed observations of a galaxy designated OJ 287 have revealed that the galaxy does not harbor a whopper supermassive black hole as had been recently thought. The findings are described in two new papers where a researcher from the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University is a coauthor on both, and a KIPAC researcher is coauthor on one. Recent estimates had pegged the mass of OJ 287's black hole at a whopping 10 billion times that of the Sun's. The new observations and theoretical work, though, suggest the black hole is far less monstrous at around 100 million solar masses. Interestingly, that new size portfolio fits with estimates made by two KIAA-affiliated researchers more than 20 years ago. Overall, the findings will help in better understanding other so-called active galaxies, where supermassive black holes at their core are gobbling up matter and spewing out radiation.

Major challenges for galaxy formation theories wrought by JWST

After not much more than a year in space, JWST continues to bring forth major new discoveries about the deep, distant universe. A recent study reports on six shockingly massive galaxies unearthed in a cosmic era just 500-700 million years after the Big Bang. Prevailing cosmological theory calls for galaxies appearing as tiny newborns then, not mature, grown-up-looking entities. Katherine "Wren" Suess, a Stanford - Santa Cruz Cosmology Fellow and a member of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University, is a coauthor of the new study. Far more research will need to be done to verify and characterize these primordial beasts, but the evident amounts of mass that have already accumulated in these early times does not jibe with what researchers had expected to find.