Neutrinos spit out by the main processes that power the sun are finally accounted for, physicists report. Two sets of nuclear fusion reactions predominate in the sun’s core and both produce the lightweight subatomic particles in abundance. Scientists had previously detected neutrinos from the most prevalent process. Now, for the first time, neutrinos from the […] More

One of the oldest known objects in the universe is wandering around the Milky Way.

Star cluster M92, a densely packed ball of stars roughly 27,000 light-years from Earth, is about 13.8 billion years old, researchers report in a paper submitted June 3 to arXiv.org. The newly refined age estimate makes this clump of stars nearly the same age as the universe.

Refining the ages of clusters like M92 can help put limits on the age of the universe itself. It can also help solve cosmic conundrums about how the universe evolved.

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The age is “on the edge of the age of the universe, as estimated by other groups,” says astronomer Martin Ying of Dartmouth College. “It helps us set the lower bound of the age of the universe. We don’t expect M92 to be born before the universe, right?”

Globular clusters like M92 are tight knots of stars that are thought to have all formed at the same time. That makes it easier for astronomers to measure the stars’ ages (SN: 7/23/21). Stars that are born at different masses have different fates: The big ones use up their fuel quickly and die young, and the small ones linger. Figuring out how many of the cluster’s stars have aged out of the main parts of their fuel-burning years gives a sense of when the whole cluster was born.

But those estimates rely on assumptions about how stellar evolution works. Ying and colleagues wanted to find an age measurement that would sidestep those assumptions.

Using a computer, the team created 20,000 synthetic stellar populations for M92, each for a different possible cluster age. They then compared the colors and brightnesses for each of these populations with Hubble Space Telescope observations of M92 and calculated the age that fit the collection best.

This isn’t the first time astronomers have measured M92’s age, but previous estimates relied on just one synthetic collection of stars. Comparing thousands of them reduced the uncertainty introduced by the assumptions baked into each one. The new technique reduced the uncertainty of the cluster age by about 50 percent, Ying says. The team found the cluster is 13.8 billion years old, give or take 750 million years. That’s strikingly close to the best estimate of the age of the universe: a smidge over 13.8 billion years, plus or minus 24 million years, according to the Planck satellite’s measurement of the first light emitted after the Big Bang (SN: 12/20/13).

The age of clusters like M92 is important partly because of a rising tension over how fast the universe is growing. Astronomers have known since the 1990s that the universe is expanding at an ever-increasing rate, thanks to a mysterious substance dubbed dark energy (SN: 8/25/22). But recent measurements of the rate of that expansion, a figure called the Hubble constant, disagree with each other (SN: 7/30/19).

One way around that tension is to accept a different age for the universe, says cosmologist and study coauthor Mike Boylan-Kolchin of the University of Texas at Austin.

“We often think about it as, Moses came down from Mount Sinai with ‘13.8 billion years’ written on some tablets or something, but it’s not quite like that,” he says. “If one takes the Hubble tension seriously, then one also has to say we don’t know the age of the universe that well.”

That’s where M92 comes in. Before spacecraft measured the cosmos’ earliest light, globular cluster ages were the best way to place limits on the age of the universe. That practice had fallen out of fashion for a while, says cosmologist Wendy Freedman of the University of Chicago, who was not involved in the new work.

But improvements in computing, theory, and measurements of the distances to clusters like M92 make it worth trying again.

“The Hubble tension itself is a really challenging nut to crack,” Freedman says. This measurement alone isn’t precise enough to settle the debate. But “the more kinds of constraints we have, the better,” she says. “It’s showing a way for the future.” More

The night sky has been brightening faster than researchers realized, thanks to the use of artificial lights at night. A study of more than 50,000 observations of stars by citizen scientists reveals that the night sky grew about 10 percent brighter, on average, every year from 2011 to 2022.

In other words, a baby born in a region where roughly 250 stars were visible every night would see only 100 stars on their 18th birthday, researchers report in the Jan. 20 Science.

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The perils of light pollution go far beyond not being able to see as many stars. Too much brightness at night can harm people’s health, send migrating birds flying into buildings, disrupt food webs by drawing pollinating insects toward lights instead of plants and may even interrupt fireflies trying to have sex (SN: 8/2/17; SN: 8/12/15).

“In a way, this is a call to action,” says astronomer Connie Walker of the National Optical-Infrared Astronomy Research Laboratory in Tucson. “People should consider that this does have an impact on our lives. It’s not just astronomy. It impacts our health. It impacts other animals who cannot speak for themselves.”

Walker works with the Globe at Night campaign, which began in the mid-2000s as an outreach project to connect students in Arizona and Chile and now has thousands of participants worldwide. Contributors compare the stars they can see with maps of what stars would be visible at different levels of light pollution, and enter the results on an app.

“I’d been quite skeptical of Globe at Night” as a tool for precision research, admits physicist Christopher Kyba of the GFZ German Research Centre for Geosciences in Potsdam. But the power is in the sheer numbers: Kyba and colleagues analyzed 51,351 individual data points collected from 2011 to 2022.

“The individual data are not precise, but there’s a whole lot of them,” he says. “This Globe at Night project is not just a game; it’s really useful data. And the more people participate, the more powerful it gets.”

Those data, combined with a global atlas of sky luminance published in 2016, allowed the team to conclude that the night sky’s brightness increased by an average 9.6 percent per year from 2011 to 2022 (SN: 6/10/16).

Most of that increase was missed by satellites that collect brightness data across the globe. Those measurements saw just a 2 percent increase in brightness per year over the last decade.

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There are several reasons for that, Kyba says. Since the early 2010s, many outdoor lights have switched from high-pressure sodium lightbulbs to LEDs. LEDs are more energy efficient, which has environmental benefits and cost savings.

But LEDs also emit more short-wavelength blue light, which scatters off particles in the atmosphere more than sodium bulbs’ orange light, creating more sky glow. Existing satellites are not sensitive to blue wavelengths, so they underestimate the light pollution coming from LEDs. And satellites may miss light that shines toward the horizon, such as light emitted by a sign or from a window, rather than straight up or down.

Satellites have missed some of the light pollution from LEDs, which emit in blue wavelengths. This image from the International Space Station shows LEDs in the center of Milan glowing brighter than the orange lights in the suburbs.Samantha Cristoforetti, NASA, ESA

Astronomer and light pollution researcher John Barentine was not surprised that satellites underestimated the problem. But “I was still surprised by how much of an underestimate it was,” he says. “This paper is confirming that we’ve been undercounting light pollution in the world.”

The good news is that no major technological breakthroughs are needed to help fix the problem. Scientists and policy makers just need to convince people to change how they use light at night — easier said than done.

“People sometimes say light pollution is the easiest pollution to solve, because you just have to turn a switch and it goes away,” Kyba says. “That’s true. But it’s ignoring the social problem — that this overall problem of light pollution is made by billions of individual decisions.”

Some simple solutions include dimming or turning off lights overnight, especially floodlighting or lights in empty parking lots.

Kyba shared a story about a church in Slovenia that switched from four 400-watt floodlights to a single 58-watt LED, shining behind a cutout of the church to focus the light on its facade. The result was a 96 percent reduction in energy use and much less wasted light , Kyba reported in the International Journal of Sustainable Lighting in 2018. The church was still lit up, but the grass, trees and sky around it remained dark.

“If it was possible to replicate that story over and over again throughout our society, it would suggest you could really drastically reduce the light in the sky, still have a lit environment and have better vision and consume a lot less energy,” he says. “This is kind of the dream.”

Barentine, who leads a private dark-sky consulting firm, thinks widespread awareness of the problem — and subsequent action — could be imminent. For comparison, he points to a highly publicized oil slick fire on the Cuyahoga River, outside of Cleveland, in 1969 that fueled the environmental movement of the 1960s and ’70s, and prompted the U.S. Congress to pass the Clean Water Act.

“I think we’re on the precipice, maybe, of having the river-on-fire moment for light pollution,” he says. More

Astronauts might one day dine on salad grown in asteroid soil.

Romaine lettuce, chili pepper and pink radish plants all grew in mixtures of peat moss and faux asteroid soil, researchers report in the July Planetary Science Journal.  

Scientists have previously grown crops in lunar dirt (SN: 5/23/22). But the new study focuses on “carbonaceous chondrite meteorites, known to be rich in volatile sources — water especially,” says astroecologist Sherry Fieber-Beyer of the University of North Dakota in Grand Forks. These meteorites, and their parent asteroids, are also rich in nitrogen, potassium and phosphorus — key agricultural nutrients. Pulverizing these types of asteroids, perhaps as part of space mining efforts, could potentially provide a ready supply of farming material in space.

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Fieber-Beyer purchased a material that mimics the space rocks’ composition and gave it to her graduate student Steven Russell. “I said, ‘All right, grow me some plants.’”

Russell, now an astrobiologist at the University of Wisconsin–Madison, chose a type of radish, lettuce and chili pepper — all of which have grown aboard the International Space Station. He, Fieber-Beyer and their colleague Kathryn Yurkonis, also of the University of North Dakota, compared how the plants grew in only faux asteroid soil, only peat moss and various mixes of the two.

Peat moss keeps soil loose and improves water retention. In all mixtures with peat moss, the plants grew. Faux asteroid soil on its own, however, compacted and couldn’t retain water, and so plants couldn’t grow.

Next, Fieber-Beyer will try growing hairy vetch seeds in that faux asteroid dirt, let the plants decay and then mix the dead plant matter throughout the soil. That, she says, could ensure that the soil doesn’t compact. Plus, seeds weigh a lot less than peat moss, making them easier to carry to space to help with any future farming attempts. More

How the Earth got its core – Science News, July 1, 1972

In the beginning, scientists believe there was an interstellar gas cloud of all the elements comprising the Earth. A billion or so years later, the Earth was a globe of concentric spheres with a solid iron inner core, a liquid iron outer core and a liquid silicate mantle…. The current theory is that the primeval cloud’s materials accreted … and that sometime after accretion, the iron, melted by radioactive heating, sank toward the center of the globe…. Now another concept is gaining ground: that the Earth may have accreted … with core formation and accretion occurring simultaneously.

Update

Most scientists now agree that the core formed as materials that make up Earth collided and glommed together and that the process was driven by heat from the smashups. The planet’s heart is primarily made of iron, nickel and some oxygen, but what other elements may dwell there and in what forms remains an open question. Recently, scientists proposed the inner core could be superionic, with liquid hydrogen flowing through an iron and silicon lattice (SN: 3/12/22, p. 12). More