October 12, 2023: Missing mass in the Milky Way, why building codes must be updated (and adhered to), and a record of violence in ancient skeletons. —Andrea Gawrylewski, Chief Newsletter Editor | | | Last year the European Space Agency's Gaia space telescope released its most precise measurements yet of the speeds and positions of nearly two billion stars in the Milky Way. The data suggested something puzzling. Stars toward the Milky Way's outer rim (which is about 50,000 light-years from the galaxy's center) seem to be orbiting far slower than similarly-situated stars in other galaxies. Stellar speeds within a galaxy can be used to estimate its total mass, and in this case, a study based on the surprisingly sluggish stars found the Milky Way coming up short: Our galaxy's gas, dust, stars and dark matter weigh in at some 200 billion times the mass of our sun, several times less than the weight reported by many earlier assessments. The Milky Way, it seems, may be "missing" about a trillion suns' worth of mass.
What's going on: Because the Milky Way's visible material hasn't disappeared (which astronomers estimate to be a mass of about 60 billion suns), one easy—and especially thought-provoking—way to explain this result is that far less dark matter is in our galaxy than previously believed. A less exciting but far more likely explanation, however, is that the analysis or even Gaia's data are somehow flawed. Or, it may merely be that the anomalously slow stars are genuine, but stars farther out (and beyond Gaia's high-precision measurements) reverse the trend and exhibit expected higher speeds—we just haven't seen them yet.
What the experts say: If confirmed, the result "would be revolutionary," says Stacy McGaugh, an astronomer at Case Western Reserve University who wasn't involved in any of the recent studies. | | | Artist impression of ESA's Gaia satellite observing the Milky Way. The background image of the sky is compiled from data from more than 1.8 billion stars. It shows the total brightness and color of stars observed by Gaia, released as part of Gaia's Early Data Release 3 (Gaia EDR3) in December 2020. Credit: Spacecraft: ESA/ATG medialab; Milky Way: ESA/Gaia/DPAC; (CC BY-SA 3.0 IGO); Acknowledgement: A. Moitinho. | | | The building codes that become law in the U.S. depend on state and local governments, resulting in a confusing patchwork. A 2020 FEMA study found that 65 percent of counties, cities and towns across the country have not adopted the most recent building codes and that 30 percent of new construction is happening in places that either have no code or have not updated it in 20 years. Why this matters: Building codes are crucial for protecting life and property, write the editors of Scientific American, in the October issue. A 2018 study in Land Economics found that houses built after Florida adopted statewide building codes based on the model codes written by the International Code Council (the group that sets the standards) saw 72 percent fewer insured losses from wind-related damage. Both FEMA and the nonprofit National Institute for Building Sciences have found that for every $1 spent on conforming to the 2018 ICC codes, $11 in damage costs are saved.
What can be done: As climate change amplifies hazards, state and local governments must update their codes. The federal government—which has limited means to influence building codes—must ramp up efforts to tie relevant state and municipal funding, such as predisaster mitigation grants, to having up-to-date building codes in place, the editors say. It should also provide more funding for jurisdictions to meet hazard-resistant codes, in addition to energy-efficient ones. | | | • Monkeys with transplanted pig kidneys lived for up to two years or more, according to a recent study. The results could help convince regulators that xenotransplantation is ready for clinical trials in humans. | 6 min read | | | • Researchers looked at ancient skeletons from Middle Eastern history between 12,000 and 400 B.C.E. and found evidence that interpersonal violence—primarily in the form of head trauma—increased significantly during times of socioeconomic upheaval and shifting climate. | 4 min read | | | • An early peak at the samples of the space rock Bennu, collected by OSIRIS-REx, shows lots of water and carbon-containing compounds. | 4 min read | | | Accumulated debris from asteroid Bennu covers a portion of the OSIRIS-REx sample collector (middle right). Scientists' initial analysis of this material shows it contains both carbon and water, two essential ingredients for life. Most of OSIRIS-REx's sample remains inside the collector. Credit: NASA/Erika Blumenfeld & Joseph Aebersold | | | • AI is already built into nearly every technology we interact with on a daily basis. The more this tech advances, the less humans will understand it and be able to intervene, writes Mark Bailey, a faculty member and chair of cyber intelligence and data science at the National Intelligence University. In order to trust new AI technologies, they must keep humans involved, he writes. | 4 min read | | | The Gaia mission is really incredible. So far its scientists have released the most extensive 3-D maps (and trajectories!) of the Milky Way ever made. You can read more about it in our coverage. I'm sure the insights from these powerful observations have just begun. | —Andrea Gawrylewski, Chief Newsletter Editor | | Subscribe to this and all of our newsletters . | | | | Scientific American
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