‘Oumuamua’s origin story

Astronomers have a new theory for the origins of ‘Oumuamua, the mysterious interstellar object that shot through our solar system in 2017: They suspect it was a chunk of nitrogen ice that was chipped off a Pluto-like exoplanet millions of years ago. ‘Oumuamua had several unique features—no visible dust or comet tail, a peculiar oblong shape, and the same reddish color as objects in the outer solar system. One Harvard University astronomer has claimed it was some kind of alien space vessel, many other scientists that it was a rocky fragment of a planet. The new theory, by two scientists at Arizona State University, hinges on the fact that ‘Oumuamua sped up as it left our solar system, most likely because melting ice was reducing its weight. The researchers modeled how ice made from hydrogen, nitrogen, and oxygen would react in similar conditions— and found nitrogen to be the most likely suspect. Moreover, the resulting nitrogen gas would have been hard to spot from Earth— explaining why astronomers couldn’t see a tail. “In essence, there was a tail like one would expect for a comet,” co-author Alan Jackson tells Space.com, “[but] because of what it is made of, we didn’t detect it.”

Times. Researchers in Sweden had 11 healthy men and women carry out a fourweek exercise regime, testing them for fitness and metabolic health throughout. The first week consisted of two short high-intensity interval training (HIIT) workouts—brief bursts of strenuous exercise on a stationary bike interspersed with a few minutes of rest. Week two involved three longer HIIT sessions; week three saw five long sessions; and in week four, the amount and intensity of the exercise was halved. In the first two weeks, volunteers got fitter, with better blood-sugar control and more total mitochondria—the tiny power plants inside cells—in their leg muscles. But in the third week, they couldn’t generate as much power while cycling, and their mitochondria produced 60 percent as much energy as before. Their metabolic health improved in the rest week, but remained below its previous level. Lead author Mikael Flockhart suspects that mitochondria get overwhelmed by the biochemical changes inside overexercised muscles.