Starlink and Astronomers Are in a Light Pollution Standoff
There's a space battle brewing just under our noses (and above our heads).
On one side are astronomers who use ground-based observatories to gather starlight from the depths of the universe. On the other are technologists, military planners and captains of industry who are rapidly cocooning our planet in ever growing swarms of starlight-spoiling satellites.
When a satellite passes through the view of a ground observatory, it can reflect sunlight back to the telescope, creating bright streaks in the resulting pictures that can obscure—or even masquerade as—astrophysical phenomena. This is especially problematic for state-of-the-art facilities such as the new Vera C. Rubin Observatory, which uses giant mirrors and the world's largest digital camera to capture ultrahigh-resolution panoramic views of the sky from a remote mountaintop in Chile. It's a 'collision of two beautiful technologies,' says Tony Tyson, the Rubin Observatory's chief scientist and an astronomer at the University of California, Davis.
[Sign up for Today in Science, a free daily newsletter]
As the satellites increase in number, with proposals for more than a million new ones currently pending, tensions are rising between those who see the sky as a wellspring of cosmic knowledge—and others who view it as a new, scarcely tapped realm of economic activity.
There are currently more than 13,000 spacecraft orbiting Earth, and more than half of them are satellites built, launched and operated by SpaceX as part of the company's sprawling Starlink megaconstellation. Starlink exists to fill the lingering gaps in global Internet connectivity, offering high-speed broadband service to customers essentially anywhere on Earth—and while it's by far the biggest player in this domain, it's not the only one.
Others include Amazon's Project Kuiper (with more than 3,200 planned satellites), Eutelsat's OneWeb (with nearly 650 satellites) and a host of Chinese projects such as Guowang, Qianfan, and Honghu-3 which each call for thousands of satellites. There's even a Starlink spin-off, Starshield, custom-built by SpaceX for the U.S. Department of Defense. Starlink's dominance makes it the poster child for megaconstellations, however—the chief target of astronomers' ire and the test case for carving out a peaceful coexistence. (In response to a request for comment, a representative from SpaceX pointed to regular updates on the company's website.)
From the beginning, Starlink engineers collaborated with astronomers to reduce the optical impacts of their satellites. Their first-generation design used dark materials and sun visors to absorb more sunlight and reduce visibility of the satellites from Earth. But the sun visors created too much drag and were scrapped in the second-generation design. In the satellites' second iteration, instead of having them absorb the light, SpaceX focused on strategically reflecting it away from Earth using a dielectric mirror film on any flat surfaces. The second-generation satellites also used a specially developed black paint to reduce the possibility of glints from other components where possible.
In a recent preprint paper posted on arXiv.org, the co-authors, who included Tyson and two SpaceX employees, analyzed the impact of these developments on the optical interference of the satellites and found that they reduced the optical interference, though even more improvements could be made.
While the Starlink satellites typically operate at a height of around 550 kilometers, Tyson and his colleagues also simulated the satellites' optical interference in orbits as low as 350 km. In the simulations, the lower altitude resulted in about a 40 percent reduction in the number of satellites entering the view of the telescope, with only a 5 percent increase in brightness (objects that are higher up can be viewed from Earth at more locations and remain in the telescope's view for longer periods).
But making a satellite orbit too low can cause undue trouble for the operators, Tyson says. A satellite in very low-Earth orbit experiences more atmospheric drag, which, if not counteracted, will hasten its orbital decay and subsequent atmospheric reentry. At this time, the Rubin Observatory's official recommendation remains that satellites orbit below 600 km, rather than at some much lower altitude.
The International Astronomical Union's Center for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS) has been reaching out to various satellite companies asking them to reduce their optical (as well as radio) interference. 'Most of the folks that we've talked to that I've interfaced with have actually been pretty open,' says Meredith Rawls, an astronomer at the University of Washington and a co-leader of the IAU CPS's SatHub initiative, 'but it doesn't scale.' CPS can't possibly reach out to all the relevant players to raise concerns and continue to follow up about their proposed solutions and their impacts. On top of that, even companies that are receptive to the CPS's concerns may not be willing to make significant changes—such as lowering satellite orbits—that would harm their bottom line.
To broadly and consistently protect the astronomical sky, governing bodies may need to pass restrictive policies. 'I don't think anyone wants zero satellites,' Rawls says, 'but at the moment, it is a pretty unregulated kind of Wild West situation that we find ourselves in.' Initiatives such as the U.S. National Science Foundation's (NSF's) satellite coordination agreements, where government agencies broker deals directly with satellite operators, could be a happy medium. So far, the NSF has signed deals with U.S. satellite companies such as Project Kuiper, OneWeb, Starlink and AST SpaceMobile to ensure these companies follow certain guidelines and avoid, to the extent possible, interfering with partner observatories.
One complication is that astronomical observations are not only affected by satellites produced in the countries they're based in. 'No single nation or entity can drive meaningful change without the coordinated action and cooperation of governments, satellite owner-operators or manufacturers, and astronomers from around the world,' wrote the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) in a conference room paper. COPUOS has yet to propose any regulations or standards for broad adoption. Instead it has recommended that member nations encourage and support collaborations between satellite manufacturers and astronomers. With growing numbers of satellite operators worldwide, however, experts believe this may not be enough.
Rubin and similar observatories are 'still going to do good science,' Rawls says. She describes the optical interference from satellites as 'bugs on the windshield': difficult and irritating—not devastating. Tyson describes the interference more like bright headlights from an approaching car, obscuring important details with a burst of light. The legacy of the Rubin Observatory, he says, will be to 'discover the unexpected'—to find things in space that astronomers never knew to look for that will 'blow everybody's mind.' But these discoveries are made less likely by the 'foreground haze' of satellite constellations. 'The scientific community will be giving up something,' Tyson says. 'I hope it isn't too much.'
It's Time to Stand Up for Science
Before you close the page, we need to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and we think right now is the most critical moment in that two-century history.
We're not asking for charity. If you become a Digital, Print or Unlimited subscriber to Scientific American, you can help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both future and working scientists at a time when the value of science itself often goes unrecognized. Click here to subscribe.
Solve the daily Crossword
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Yahoo
4 hours ago
- Yahoo
X-ray telescope finds something unexpected with the 'heartbeat black hole'
When you buy through links on our articles, Future and its syndication partners may earn a commission. A black hole's bizarre "heartbeat" is forcing astronomers to reconsider how these cosmic heavyweights behave. Observations of IGR J17091-3624 — a black hole in a binary system roughly 28,000 light-years from Earth — were taken using NASA's Imaging X-ray Polarimetry Explorer (IXPE). Nicknamed the "heartbeat" black hole for its dramatic, rhythmic pulses in brightness, the object feeds on matter stolen from a companion star. The black hole's pulses are the result of fluctuations in the superheated plasma swirling around it (also known as the accretion disk) and the inner region called the corona, which can reach extreme temperatures and radiate incredibly luminous X-rays. IXPE measured the polarization — the direction of the black hole's X-rays — to determine the alignment of its vibrations. The space probe recorded a surprising 9.1% polarization degree, which is much higher than theoretical models predicted, according to a statement from NASA. Studying the polarization degree offers insight about the geometry of the black hole and motion of matter nearby. Typically, such high readings suggest the corona is viewed almost edge-on, where its structure appears highly ordered. However, other observations of IGR J17091-3624 don't seem to match that picture, leaving scientists with a puzzling contradiction. Astronomers tested two different models to help explain the recent observations of IGR J17091-3624. One posits that powerful winds are being launched from the accretion disk, scattering X-rays into a more polarized state even without an edge-on perspective. The other suggests the corona itself is moving outward at extraordinary speeds, causing relativistic effects that amplify polarization. Simulations of both scenarios reproduce the IXPE results, but each model challenges long-held assumptions about black hole environments. "These winds are one of the most critical missing pieces to understand the growth of all types of black holes," Maxime Parra, co-author of the study from Ehime University in Matsuyama, Japan, said in the statement. "Astronomers could expect future observations to yield even more surprising polarization degree measurements." Their findings were published May 27 in the journal Monthly Notices of the Royal Astronomical Society. Solve the daily Crossword
Yahoo
7 hours ago
- Yahoo
A braided stream, not a family tree: How new evidence upends our understanding of how humans evolved
When you buy through links on our articles, Future and its syndication partners may earn a commission. Our species is the last living member of the human family tree. But just 40,000 years ago, Neanderthals walked the Earth, and hundreds of thousands of years before then, our ancestors overlapped with many other hominins — two-legged primate species. This raises several questions: Which other populations and species did our ancestors mate with, and when? And how did this ancient mingling shape who we are today? "Everywhere we've got hominins in the same place, we should assume there's the potential that there's a genetic interaction," Adam Van Arsdale, a biological anthropologist at Wellesley College in Massachusetts, told Live Science. In other words, different hominin species were having sex — and babies — together. This means our evolutionary family tree is tangled, with still-unknown relatives possibly hiding in the branches. Emerging DNA evidence suggests this "genetic interaction" resulted in the diversity and new combinations of traits that helped ancient humans — including our ancestors — thrive in different environments around the globe. "It's all about variation," Rebecca Ackermann, a biological anthropologist at the University of Cape Town in South Africa, told Live Science. "More variation in humans allows us to be more flexible as a species and, as a result, be more successful as a species because of all the diversity." Cutting-edge techniques may illuminate the crucial periods deeper in our evolutionary past that led to Homo sapiens evolving in Africa, or even shed light on periods before the Homo genus existed. That knowledge, in turn, could improve our understanding of exactly what makes us human. Related: Lucy's last day: What the iconic fossil reveals about our ancient ancestor's last hours A braided stream In the early 20th century, scientists thought there was a clear evolutionary line between our ancestors and us, with one species sequentially evolving into another and no contribution from "outside" populations, like the branches on a tree. But 21st-century advances in ancient DNA analysis techniques have revealed that our origins are more like a braided stream — an idea borrowed from geology, where shallow channels branch off and rejoin a stream like a network. "It becomes very hard when you think about things in more of a braided stream model to divide [populations] into discrete groups," Ackermann said. "There are not, by definition, any discrete groups; they have contributed to each other's evolution." Ackermann studies variation and hybridization — the exchange of genes between different groups — across the evolutionary history of hominins, to better understand how genetic and cultural exchange made us human. And she thinks hybridization both within and outside Africa played a significant role in our origins. Evidence of such hybridization has come out in a steady stream since the first Neanderthal genome was sequenced in 2010. That research program, which earned geneticist Svante Pääbo a Nobel Prize in 2022, revealed that H. sapiens and Neanderthals regularly had sex. It also led to the discovery of the Denisovans, a previously unknown population that ranged across Asia from about 200,000 to 30,000 years ago and that also had offspring with both Neanderthals and H. sapiens. "You have so much complexity that it makes no sense to say there was only one origin of sapiens. There can't be one universal model that explains literally every human on Earth." Sheela Athreya, Texas A&M University When species share genes with one another through hybridization, the process is known as introgression, and when those shared genes are beneficial to a population, it's known as adaptive introgression. Emerging from two decades of gene studies of humans and our extinct relatives is the understanding that we may be who we are thanks to a proclivity to pair off with anyone — including other species. Connecting with other groups — socially and sexually — was an important part of human evolution. "For us to survive and become human probably really depended on that," Van Arsdale said. Benefits of hybridization Since the first Neanderthal genome was sequenced, researchers have attempted to identify when and how often our H. sapiens ancestors mated with other species and groups. They've also investigated how Neanderthal and Denisovan genes affect us today. Many of these studies rely on large datasets of genomes from humans living today and tie them back to ancient DNA extracted from the bones of extinct humans and their relatives who lived tens of thousands of years ago. These analyses show that many genes that originated in now-extinct groups may confer advantages to us today. For instance, modern Tibetans have a unique gene variant for high-altitude living that they likely inherited from the Denisovans, while different versions of Neanderthal skin pigment genes may have helped some populations adapt to less-sunny climates while protecting others from UV radiation. There is also evidence that Neanderthal genes helped early members of our species adapt quickly to life in Europe. Given their long history in Europe prior to the arrival of H. sapiens, Neanderthals had built up a suite of genetic variations to deal with diseases unique to the area. H. sapiens encountered these novel diseases when they spread into areas where Neanderthals lived. But, by mating with Neanderthals, they also got genes that protected them from those viruses. Beyond specific traits that may confer advantages in humans today, these episodes of mating diversified the human gene pool, which may have helped our ancestors weather varied environments. The importance of modern genetic diversity can be illustrated with human leukocyte antigen (HLA) genes, which are critical to the human immune system's ability to recognize pathogens. Humans today have a dizzying array of these genes, especially in eastern Asia. This area of the world is a "hotspot" for emerging infectious diseases due to a combination of biological, ecological and social factors, so this diversity may provide advantages in an area where new diseases are frequently emerging. When genetic diversity is lost through population isolation and decline, groups may become particularly susceptible to new infections or unable to adapt to new ecological circumstances. For instance, one theory holds that Neanderthal populations declined and eventually went extinct around 40,000 years ago because they lacked genetic diversity due to inbreeding and isolation. Related: Did we kill the Neanderthals? New research may finally answer an age-old question. Discovery of "ghost populations" Some of the newest research goes deeper into evolutionary time, identifying "ghost populations" — human groups that went extinct after contributing genes to our species. Often, archaeologists have no skeletal remains from these populations, but their echoes linger in our genome, and their existence can be gleaned by modeling how genes change over time. For instance, a "mystery population" of up to 50,000 individuals that interbred with our ancestors 300,000 years ago passed along genes that created more connections between brain cells, which may have boosted our brain functioning. The population that hybridized with H. sapiens and helped boost our brains may have been a lineage of Homo erectus. This species was once thought to have disappeared after evolving into H. sapiens in Africa, but anthropologists now think H. erectus survived in parts of Asia until 115,000 years ago. In fact, our evolutionary history may include the mating of populations that had been separated for up to a million years, Van Arsdale said. These "superarchaic" populations are increasingly being discovered as we mine our own genomes and those of our close relatives, Neanderthals and Denisovans. For instance, a genetic study published in 2020 identified a superarchaic population that separated from other human ancestors about 2 million years ago but then interbred with the ancestors of Neanderthals and Denisovans around 700,000 years ago. Experts don't know exactly what genes this superarchaic ghost population shared with our ancestors or who it was, but it may have been a lineage of H. erectus. Evolutionary blank space But there's a large, unmapped region of human evolutionary history — and it's crucial for our identity as a species. The period when H. sapiens was first evolving in Africa, and the more distant period of human evolutionary history on the continent that predates the Homo genus, remains a huge knowledge gap. That's in part because DNA preserves well in caves and other stable environments in frigid areas of the world, like those found in areas of Europe and Asia, while Africa's warmer conditions usually degrade DNA. As a result, the most ancient complete human DNA sequence from Africa is just 18,000 years old. By contrast, a skeleton discovered in northern Spain produced a full mitochondrial genome from a human relative, H. heidelbergensis, who lived more than 300,000 years ago. "Maps of human ancient DNA are overwhelmingly Eurasian data," Van Arsdale said. "And the reality is that's a marginal place in our evolutionary past. So to understand what was happening in the core of Africa would be potentially transformative." This is where current DNA technology falls short. Small hominins that walked on two legs, called australopithecines, evolved around 4.4 million years ago in Africa. And between 3 million and 2 million years ago, our genus, Homo, likely evolved from them. H. sapiens evolved around 300,000 years ago in Africa and then traveled around the world. But given the scarcity of ancient DNA from Africa, it is difficult to figure out which groups were mating and hybridizing in that vast time span, or how the fossil skeletons of human relatives from the continent were related. Related: 'It makes no sense to say there was only one origin of Homo sapiens': How the evolutionary record of Asia is complicating what we know about our species A new technique called paleoproteomics could help shed light on our African origin as a species and even reveal clues about the genetic makeup of australopithecines and other related hominins. Because genes are the instructions that code for proteins, identifying ancient proteins trapped in tooth enamel and fossil skeletons can help scientists determine some of the genes that were present in populations that lived millions of years ago. Still, it's a very new technique. To date, paleoproteomic analysis has identified only a handful of incomplete protein sequences in ancient human relatives and has thus far been able to glean only a small amount of genetic information from those. But in a landmark study published this year, researchers used proteins in tooth enamel to figure out the biological sex of a 3.5 million-year-old Australopithecus africanus individual from South Africa. And in another study, also published this year, scientists used tooth enamel from a 2 million-year-old human relative, Paranthropus robustus, to identify genetic variability among four fossil skeletons — a finding that suggests they may have been from different groups, or even different species. Paleoproteomics is still pretty limited, though. In a recent study, scientists analyzed a dozen ancient proteins found in fossils of Neanderthals, Denisovans, H. sapiens and chimpanzees. They found that these proteins could help reconstruct a family tree down to the genus level, but were not useful at the species level. Still, the fact that protein data can be used to reconstruct part of the braided stream of early humans and to identify the chromosomal sex of human relatives is encouraging, and further research along these lines is needed, experts told Live Science. Some are confident new approaches could help us unpack these early interactions. "I think we're going to learn a lot more about Africa's ancient past in the next two decades than we have so far," Van Arsdale said. Ackermann is more cautious. To really understand when, where and with whom our human ancestors mated and how that made us who we are, "we need to have a whole genome" from these ancient human relatives, she said. "With proteins, you just don't get that." Sheela Athreya, a biological anthropologist at Texas A&M University, is optimistic that we can use these new techniques to tease apart our more distant evolutionary past — and that it will yield surprises. For instance, she thinks what we now call Denisovans may actually have been H. erectus. RELATED STORIES —DNA has an expiration date. But proteins are revealing secrets about our ancient ancestors we never thought possible. —28,000-year-old Neanderthal-and-human 'Lapedo child' lived tens of thousands of years after our closest relatives went extinct —Never-before-seen cousin of Lucy might have lived at the same site as the oldest known human species, new study suggests "Absolutely in my lifetime, someone will be able to get a Homo erectus genome," Athreya said, likely from colder areas of Asia. "I'm excited. I think it'll look Denisovan." Either way, it's clear that a whole lot of mixing made us human. The Homo lineage may have first evolved in Africa, Athreya said. "But once it left Africa, you have so much complexity that it makes no sense to say there was only one origin of sapiens. There can't be one universal model that explains literally every human on Earth."
Yahoo
8 hours ago
- Yahoo
Hubble reveals new details about alien comet 3I/ATLAS
Hubble has captured the sharpest images to date of interstellar object 3I/ATLAS, revealing new details about this icy alien traveller. The discovery of the third interstellar object passing through our solar system has the astronomy community fairly excited. Given the limited amount of time we have to observe 3I/ATLAS before it leaves our solar system, never to be seen again, astronomers want to find out as much as they can about it, while they have a chance. To this end, increasingly more powerful telescopes are being turned towards 3I/ATLAS. Ground-based observatories have been delivering images, so far, giving researchers a chance to make educated guesses at the nature of the object and how big it is. On July 21, astronomers got their first look at 3I/ATLAS using the Hubble Space Telescope. Hubble's first image of Comet 3I/ATLAS. The streaks in the background are distant stars, drawn out into lines as the telescope tracked the moving object. According to NASA, a blue filter was used for these observations. (Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI)) With 3I/ATLAS currently surrounded by a cloud of dust, ice, and gas (its 'coma'), the solid nucleus of the comet cannot be seen, even by Hubble. However, these observations give astronomers a better estimate of the size of this alien object, simply by comparing what they're seeing with the behaviour of 'home grown' comets. From ground observatories, based on its brightness, the original best estimate for the size of its nucleus was anywhere from 10-20 kilometres in diameter. New data from Hubble has significantly reduced that, putting an upper limit on the comet's size of 5.6 kilometres wide. That's still substantially larger than both 2I/Borisov and 1I/'Oumuamua, which were estimated at being roughly 500 metres wide and 100 metres wide, respectively. Still, the researchers who took the Hubble observations believe it's possible 3I/ATLAS's nucleus could be as small as just 320 metres across. Hubble's view of 3I/ATLAS. The comet is travelling from left to right in this field of view, with the Sun generally located off the right edge of the image. (Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI)) The image captured by Hubble also reveals more detail, confirming 3I/ATLAS's cometary nature. As seen above, the solid nucleus is located within the bright region on the left side of the fuzzy 'teardrop'. The diffuse region on the right appears to be a plume of dust being ejected from it, as sunlight warms the nucleus' surface. Comets produce tails of dust and ionized gas, which both generally point away from the Sun. However, this kind of dust plume being generated in the direction of the Sun is apparently common in comets when they are farther out in space and first begin to feel the Sun's heat. Additionally, according to NASA, the researchers report seeing the hints of a dust tail streaming away from the nucleus. We still have roughly a month before most telescopes will lose sight of comet 3I/ATLAS as it passes around the other side of the Sun. At that time, orbiters around Mars might get a better look. Then, starting in early December, astronomers will pick up observations of it again, and have at least until early 2026 before it gets too far away to see. "Observations from other NASA missions including the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory, as well as NASA's partnership with the W.M. Keck Observatory, will help further refine our knowledge about the comet, including its chemical makeup," says NASA. Watch below: August Sky Guide — Watch for a six planet parade Click here to view the video Solve the daily Crossword
