https://www.cnn.com/2019/05/31/world/spitzer-celestial-family-photo-trnd-scn/index.html
2019-05-31 14:08:00Z
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One hundred years ago today, on May 29, 1919, measurements of a solar eclipse offered verification for Einstein's theory of general relativity. Even before that, Einstein had developed the theory of special relativity, which revolutionized the way we understand light. To this day, it provides guidance on understanding how particles move through space—a key area of research to keep spacecraft and astronauts safe from radiation.
The theory of special relativity showed that particles of light, photons, travel through a vacuum at a constant pace of 670,616,629 miles per hour—a speed that's immensely difficult to achieve and impossible to surpass in that environment. Yet all across space, from black holes to our near-Earth environment, particles are, in fact, being accelerated to incredible speeds, some even reaching 99.9% the speed of light.
One of NASA's jobs is to better understand how these particles are accelerated. Studying these superfast, or relativistic, particles can ultimately help protect missions exploring the solar system, traveling to the Moon, and they can teach us more about our galactic neighborhood: A well-aimed near-light-speed particle can trip onboard electronics and too many at once could have negative radiation effects on space-faring astronauts as they travel to the Moon—or beyond.
Here are three ways that acceleration happens.
1. Electromagnetic Fields
Most of the processes that accelerate particles to relativistic speeds work with electromagnetic fields—the same force that keeps magnets on your fridge. The two components, electric and magnetic fields, like two sides of the same coin, work together to whisk particles at relativistic speeds throughout the universe.
In essence, electromagnetic fields accelerate charged particles because the particles feel a force in an electromagnetic field that pushes them along, similar to how gravity pulls at objects with mass. In the right conditions, electromagnetic fields can accelerate particles at near-light-speed.
On Earth, electric fields are often specifically harnessed on smaller scales to speed up particles in laboratories. Particle accelerators, like the Large Hadron Collider and Fermilab, use pulsed electromagnetic fields to accelerate charged particles up to 99.99999896% the speed of light. At these speeds, the particles can be smashed together to produce collisions with immense amounts of energy. This allows scientists to look for elementary particles and understand what the universe was like in the very first fractions of a second after the Big Bang.
2. Magnetic Explosions
Magnetic fields are everywhere in space, encircling Earth and spanning the solar system. They even guide charged particles moving through space, which spiral around the fields.
When these magnetic fields run into each other, they can become tangled. When the tension between the crossed lines becomes too great, the lines explosively snap and realign in a process known as magnetic reconnection. The rapid change in a region's magnetic field creates electric fields, which causes all the attendant charged particles to be flung away at high speeds. Scientists suspect magnetic reconnection is one way that particles—for example, the solar wind, which is the constant stream of charged particles from the sun—is accelerated to relativistic speeds.
Those speedy particles also create a variety of side-effects near planets. Magnetic reconnection occurs close to us at points where the sun's magnetic field pushes against Earth's magnetosphere—its protective magnetic environment. When magnetic reconnection occurs on the side of Earth facing away from the sun, the particles can be hurled into Earth's upper atmosphere where they spark the auroras. Magnetic reconnection is also thought to be responsible around other planets like Jupiter and Saturn, though in slightly different ways.
NASA's Magnetospheric Multiscale spacecraft were designed and built to focus on understanding all aspects of magnetic reconnection. Using four identical spacecraft, the mission flies around Earth to catch magnetic reconnection in action. The results of the analyzed data can help scientists understand particle acceleration at relativistic speeds around Earth and across the universe.
3. Wave-Particle Interactions
Particles can be accelerated by interactions with electromagnetic waves, called wave-particle interactions. When electromagnetic waves collide, their fields can become compressed. Charged particles bouncing back and forth between the waves can gain energy similar to a ball bouncing between two merging walls.
These types of interactions are constantly occurring in near-Earth space and are responsible for accelerating particles to speeds that can damage electronics on spacecraft and satellites in space. NASA missions, like the Van Allen Probes, help scientists understand wave-particle interactions.
Wave-particle interactions are also thought to be responsible for accelerating some cosmic rays that originate outside our solar system. After a supernova explosion, a hot, dense shell of compressed gas called a blast wave is ejected away from the stellar core. Filled with magnetic fields and charged particles, wave-particle interactions in these bubbles can launch high-energy cosmic rays at 99.6% the speed of light. Wave-particle interactions may also be partially responsible for accelerating the solar wind and cosmic rays from the sun.
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Citation: Three ways to travel at (nearly) the speed of light (2019, May 31) retrieved 31 May 2019 from https://phys.org/news/2019-05-ways.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Light-speed travel is a staple of science fiction in space. No "Star Wars" movie seems complete until the Millennium Falcon (or a rival ship) uses its hyperdrive. And many "Star Trek" fans enjoy talking about the relative star-system-jumping speeds of the USS Enterprise, against the speeds of other Federation ships.
But in real life, physics gets in the way. Einstein's theory of special relativity essentially puts a speed limit on cosmic travel; as far as we can tell, nothing goes faster than the speed of light. Worse, any object that has mass tends to get more and more massive — dragging down the object's velocity — as it approaches light speed. So as far as we know, only small particles can get anywhere near the speed of light.
One hundred years ago, on May 29, 1919, scientists performed measurements of a solar eclipse that confirmed Einstein's work. To celebrate, NASA offered three ways that particles can accelerate to amazing speed in a new statement.
Related: Why Don't We Have a 'Star Wars' Hyperdrive Yet?
The sun is a wacky environment to study physics, because it is so extreme compared to Earth. It's also a real-life laboratory showing how nuclear reactions happen. It also is an example of an environment with electromagnetic fields — which, as NASA points out, is the same force that stops magnets from falling off your fridge.
Magnetic fields and electric fields work together to accelerate particles with an electric charge. This charge allows electromagnetic fields to push particles along — sometimes at speeds approaching the speed of light.
We can even simulate this process on Earth. Huge particle accelerators (like at the Department of Energy's Fermi National Accelerator Laboratory, or at the European Organization for Nuclear Research's Large Hadron Collider) create pulsed electromagnetic fields. These fields accelerate charged particles close to the speed of light. Next, scientists often crash these particles together to see what particles and energy are released.
In fractions of a second after these collisions, we can quickly observe elementary particles that were around in the first few seconds after the universe was formed. (That event, called the Big Bang, happened about 13.8 billion years ago.)
The sun is also host to phenomena called solar flares. Dancing above the sun's surface is a tangle of magnetic fields. At times, these fields intersect and snap, sending plumes of solar material off the surface — and, sometimes, charged particles along with it.
"When the tension between the crossed lines becomes too great, the lines explosively snap and realign in a process known as magnetic reconnection," NASA officials said in the statement. "The rapid change in a region's magnetic field creates electric fields, which causes all the attendant charged particles to be flung away at high speeds."
Particles streaming off the sun may accelerate close to the speed of light, thrown from the sun thanks to magnetic reconnection. One example of such objects is the solar wind, the constant stream of charged particles the sun emits into the solar system. (There may be other factors speeding these particles as well, such as wave-particle interactions — which is explained in the next section of this article.)
Magnetic reconnection also likely happens at large planets, such as Jupiter and Saturn. Closer to home, NASA studies magnetic reconnection near Earth using the Magnetospheric Multiscale mission, which measures our planet's magnetic field using four spacecraft. The results may be useful to better understand how particles accelerate all over the universe, NASA officials said.
Particles can also careen at high speeds when electromagnetic waves collide; that phenomenon is more technically called wave-particle interactions.
"When electromagnetic waves collide, their fields can become compressed. Charged particles bouncing back and forth between the waves can gain energy similar to a ball bouncing between two merging walls," NASA officials said.
These interactions take place all over the universe. Near Earth, NASA missions such as the Van Allen probes are watching wave-particle interactions to better predict particle movements — and protect electronics on satellites. That's because high-speed particles can damage these delicate spacecraft parts.
Supernovas, or star explosions, may also play a role in more far-away interactions. Researchers have theorized that after a star explodes, it creates a blast wave — a shell of hot, dense compressed gas — that zooms away from the stellar core at high speed. These bubbles are full of charged particles and magnetic fields, creating a likely environment for wave-particle interactions. This process may eject high-energy cosmic rays — which consist of particles — at velocities close to the speed of light.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.
Work opens a path to precise calculations of the structure of other nuclei.
In a study that combines experimental work and theoretical calculations made possible by supercomputers, scientists have determined the nuclear geometry of two isotopes of boron. The result could help open a path to precise calculations of the structure of other nuclei that scientists could experimentally validate.
Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory, in collaboration with scientists in Germany and Poland, determined the difference in a quantity known as the nuclear charge radius between boron-10 and boron-11. The nuclear charge radius indicates the size of an atomic nucleus—which often has relatively indistinct edges.
Nuclear charge radii are difficult to compute with high precision for atoms much larger than boron because of the sheer number of neutrons and protons whose properties and interactions must be derived from quantum mechanics.
Nuclear theory builds from quantum chromodynamics (QCD), a set of physical rules that apply to quarks and gluons that compose the protons and neutrons within the nucleus. But trying to solve the nuclear dynamics using QCD alone would be an almost impossible task due to its complexity, and researchers have to rely on at least some simplifying assumptions.
Because boron is relatively light—with only five protons and a handful of neutrons—the team was able to successfully model the two boron isotopes on the Mira supercomputer and study them experimentally using laser spectroscopy. Mira is part of the Argonne Leadership Computing Facility (ALCF), a DOE Office of Science User Facility.
"This is one of the most complicated atomic nuclei for which it is possible to arrive at these precise measurements experimentally and derive them theoretically," said Argonne nuclear physicist Peter Mueller, who helped lead the study.
Looking at how the nuclear configurations of boron-11 (11B) and boron-10 (10B) differed involved making determinations at extraordinarily small length scales: less than a femtometer—one-quadrillionth of a meter. In a counterintuitive finding, the researchers determined that the 11 nucleons in boron-11 actually occupy a smaller volume than the 10 nucleons in boron-10.
To look experimentally at the boron isotopes, scientists at the University of Darmstadt performed laser spectroscopy on samples of the isotopes, which fluoresce at different frequencies. While most of the difference in the fluorescence patterns is caused by the difference in the mass between the isotopes, there is a component in the measurement that reflects the size of the nucleus, explained Argonne physicist Robert Wiringa.
To separate these components, collaborators from the University of Warsaw and Adam Mickiewicz University in Poznan carried out state-of-the-art atomic theory calculations that precisely describe the complicated dance of the five electrons around the nucleus in the boron atom.
"Earlier electron scattering experiments couldn't really say for sure which was bigger," Wiringa said. "By using this laser spectroscopy technique, we're able to see for certain how the extra neutron binds boron-11 more closely."
The good agreement between experiment and theory for the dimensions of the nucleus allows researchers to determine other properties of an isotope, such as its beta decay rate, with higher confidence. "The ability to perform calculations and do experiments go hand-in-hand to validate and reinforce our findings," Mueller said.
The next stage of the research will likely involve the study of boron-8, which is unstable and only has a half-life of about a second before it decays. Because there are fewer neutrons in the nucleus, it is much less tightly bound than its stable neighbors and is believed to have an extended charge radius, Mueller said. "There is a prediction, but only experiment will tell us how well it actually models this loosely bound system," he explained.
An article based on the research, "Nuclear Charge Radii of 10,11B," appears in the May 10 issue of Physical Review Letters.
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Citation: Experiments and calculations allow examination of boron's complicated dance (2019, May 31) retrieved 31 May 2019 from https://phys.org/news/2019-05-boron-complicated.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
New research shows that several species of African mole-rats have evolved an uncanny ability to ward off certain types of pain, including discomfort wrought by acid, chili peppers, and hot mustard. These insights could eventually lead to advanced pain-relieving therapies in humans.
They’re not the prettiest things on the planet, but mole-rats are unquestionably cool.
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The iconic naked mole-rat, with its ability to resist cancer and oxygen deprivation and seemingly death itself, tends to get much of the research attention, but there are several other species of mole-rats with plenty to offer. New research published today in Science shows that multiple species African mole-rats have acquired an insensitivity to certain kinds of pain. Genetic endowments allow these subterranean rodents to thrive in otherwise inhabitable abodes, such as burrows crawling with venomous ants.
The new study, led by Karlien Debus and Ole Eigenbrod from the Max Delbrück Center for Molecular Medicine in Germany, is a follow-up to work done on naked-mole rats back in 2008. The previous study, led by Thomas Park from the University of Illinois at Chicago, showed that naked-mole rats were surprisingly impervious to pain induced by acid and capsaicin, the latter of which gives chili peppers their heat.
The new study, which also involved Park, tested pain insensitivity across several other species of rodents, including nine species of African mole-rats and the common mouse. They wanted to explore the molecular factors responsible for pain insensitivity, with the hope that such insights could lead to the development of highly effective analgesics for people.
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For the study, the researchers administered three substances that typically cause burning sensations in humans and other animals. Importantly, these substances weren’t chosen arbitrarily—they’re the kinds of things that mole-rats have to contend with on a regular basis. Specifically, the mole-rats were exposed to diluted hydrochloric acid (an analogue for ant venom), capsaicin (an ingredient often found in mole-rat foods), and allyl isothiocyanate AITC (an irritant found in roots—another mole-rat favorite—that gives wasabi and hot mustard their punch). In an email to Gizmodo, Debus described these substances as being all natural and with no long-term toxic properties, while adding that the experiments were approved by ethical commissions in Germany, South Africa, and Chicago.
During the behavioral assessment of pain, small amounts of these substances were injected into the paws of the animals. Rodents displayed discomfort to a compound by licking or lifting their paws, a process that typically lasted about five minutes. Animals that were impervious to the pain conducted themselves as usual, such as walking around and showing normal digging and exploratory behaviors.
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A total of three unrelated mole-rat species, the cape mole-rat, the naked mole-rat, and the East African root rat, shrugged off the acid like it was nothing. Two species, the natal mole-rat and the naked mole-rat, showed an insensitivity to capsaicin. The highveld mole-rat was able to ward off the unpleasant effects of AITC, highlighting a unique genetic adaptation to the substance.
“Most likely, the animals have acquired this remarkable trait to adapt to living in a certain environment,” Debus told Gizmodo. “The case of the highveld mole-rat sharing its burrows with ants producing a normally painful substance is a wonderful example of how environment shapes evolution over the long term.”
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Specifically, the highveld mole-rat was observed to co-exist with the noxious Natal droptail ants, a discovery made by Daniel Hart, a PhD student at the University of Pretoria and a co-author of the new study.
“Without the knowledge of the South African zoologists, this paper would not be the same,” said Debus. “This is what I love about the paper, how molecular biology, evolution, and zoology all come together.”
Indeed, the new study also involved some very important and revealing molecular biology. Genetic sequencing technology, along with an analysis of brain and spinal cord tissue taken from the specimens, allowed the researchers to pinpoint the genes and molecular pathways responsible for these heroic abilities.
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“This study makes exciting insights into the biology of pain, by identifying that highveld mole-rats show no pain response to AITC, the chemical that gives wasabi and mustard their pungency,” neuropharmacologist Ewan St. John Smith from Corpus Christi College wrote in an email to Gizmodo. “This is due to increased activity of a particular molecule called NALCN in their pain-sensing nerves. The researchers used numerous techniques to attack their hypothesis from different directions, always reaching the same endpoint—that increased NALCN activity underpins the highveld mole-rat’s insensitivity to AITC,” said Smith, who wasn’t involved in the new study.
The researchers used drugs to block NALCN in the highveld mole-rats, which in turn restored the pain sensitivity to AITC and, by logical extension, to the Natal droptail ant venom. This “shows the potential for using drugs to modulate NALCN activity to treat pain in humans,” said Smith. This is good, he added, because clinicians need more weapons in their arsenal for treating pain in different people.
“[T]his study demonstrates the power of studying naturally occurring differences in pain sensitivity,” he said. “For scientists to manage in a few years what evolution has produced over millennia is perhaps an unfair challenge!”
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Astronomers have used a desert-based observatory to identify an exoplanet that falls in the middle of what scientists had dubbed the Neptunian Desert.
That term refers to a phenomenon that astronomers had noticed by which there seemed to be an absence of Neptune-size planets that orbit their star in less than four days. The newly discovered planet is formally known as NGTS-4b but nicknamed "The Forbidden Planet" for its supposed implausibility.
"This planet must be tough — it is right in the zone where we expected Neptune-sized planets could not survive," lead author Richard West, an astronomer at the University of Warwick in the U.K., said in a statement. "It is truly remarkable that we found a transiting planet via a star dimming by less than 0.2% — this has never been done before by telescopes on the ground."
Related: The Most Fascinating Exoplanets Found Last Year
The "Forbidden Planet" orbits a star called NGTS-4, which is located about 920 light-years away from Earth. The planet seems to circle its star once every 1.3 Earth-days, and it is about 20 times the mass and 3 times the radius of Earth. It also seems to retain an atmosphere, which particularly surprised the researchers, since at such a close distance to its star it would be difficult for the planet to cling to gas.
The researchers believe that the planet may exist despite its location because it formed elsewhere and migrated into the Neptunian Desert zone within the last million years or so. It could also have been born much larger and be gradually losing material.
The planet was first spotted in data gathered by the Next-Generation Transit Survey telescope, located in the mountains of the Atacama Desert of Chile. The team used a range of other telescopes to conduct follow-up observations that made them more confident in the detection and characterization of NGTS-4b.
And they hope to build on the new research to find the "Forbidden Planet" some company. "We are now scouring out data to see if we can see any more planets in the Neptune Desert," West said in the statement. "Perhaps the desert is greener than was once thought."
The research is described in a paper published April 20 in the journal the Monthly Notices of the Royal Astronomical Society.
Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.
When astronomers search for exoplanets they rarely know what they’re going to find, but that doesn’t mean there aren’t rules that would-be planets are expected to follow. Depending on their distance from their host star, any given planet will fall into one of several categories… or at least that’s what scientists have come to expect.
NGTS-4b, a newly-discovered world orbiting a distant star, doesn’t follow many of the rules that researchers thought they knew, and it’s earned the nickname “The Forbidden Planet” because of it.
NGTS-4b was detected by scientists with the European Southern Observatory. The planet lies in an area known as the Neptunian Desert, which is the name given to the region immediately surrounding a star where planets of similar size to Neptune are almost never found.
This area is extremely close to the star, and it’s that makes it incredibly hostile. Planets found in this region are typically stripped bare of their atmosphere which is blown out into space by the energy put out by the host star.
NGTS-4b is a rare exception to this rule, as it appears to still have its atmosphere intact. That’s rather shocking, especially when you consider that it’s so close to its star that it completes an entire orbit in less than two Earth days. Earth, by comparison, takes a year to complete that same trip. The planet is estimated to be around 1,000 degrees Celsius.
“This planet must be tough—it is right in the zone where we expected Neptune-sized planets could not survive,” lead author Dr. Richard West of the University of Warwick said in a statement. “We are now scouring out data to see if we can see any more planets in the Neptune Desert—perhaps the desert is greener than was once thought.”
It’s likely, the researchers say, that the planet only recently traveled into its incredibly close orbit with its star, and that big changes are likely to happen within the next million years or so as its atmosphere is blasted away by its star.
Over the weekend, astronomers and space enthusiasts everywhere caught a glimpse of SpaceX’s recently launched Starlink satellites in the sky. They’re the first 60 spacecraft of nearly 12,000 the company plans to launch for its massive “internet from space” initiative. For many on the internet, it was an amazing sight to see. For the astronomy community, it was devastating to watch.
The satellites, strung out like a line of glowing army ants, shone brightly as they moved along their orbit around Earth, clearly visible to the naked eye. Now, many in the astronomy community are concerned that this mega constellation might be too bright, and the sheer number of satellites that SpaceX wants to launch could muck up their telescope observations of the Universe.
“It’s going to become increasingly likely that the satellites will pass through the field of view and essentially contaminate your view of the Universe,” Darren Baskill, an outreach officer of physics and astronomy at the University of Sussex, tells The Verge. “And it’s going to be really difficult to remove that contamination away from our observations.”
Satellites are already an issue for astronomers studying celestial objects in deep space. In order to get detailed images of objects many light-years away from Earth, astronomers take long-exposure shots of the sky with their telescopes. This type of imaging entails leaving the telescope exposed to light for minutes or hours. As a result, scientists can gather light from a very distant, faint object and figure out more about it. For instance, it’s a great way to learn what kinds of gases are in a faraway galaxy. Each type of gas emits different types of light, which astronomers can detect and identify.
VIDEO! Prepare to be mind-blown!
— Dr Marco Langbroek (@Marco_Langbroek) May 24, 2019
The train of @SpaceX #Starlink satellites passing over Leiden, the Netherlands, some 25 minutes ago. Camera: WATEC 902H with Canon FD 1.8/50 mm lens. I was shouting when they entered FOV!@elonmusk https://t.co/xChLDH32uk
But whenever a super bright object passes through the field of view of a long-exposure shot, the observation gets muddied. The light from that object tears through the image, causing a long, bright streak through the sky. Satellites can be particularly bright since they’re often made with reflective materials or have solar panels that bounce light from the Sun. “If it was just a point in an image, that wouldn’t be too bad,” Phil Bull, a theoretical cosmologist at Queen Mary University of London, tells The Verge. “You could just ignore the bit around that point. But because it’s a big line going through your image, it really gets in the way.”
Currently, there are about 5,000 satellites in orbit around Earth, around 2,000 of which are still operational, according to the most recent report from the European Space Agency. These objects already cause the occasional streak and headache for astronomers. But with the addition of SpaceX’s Starlink constellation, as well as other proposed mega constellations from OneWeb, Telesat, Kepler Communications, and now Amazon, the number of operational satellites could increase significantly. And that could drastically up the risk of satellites streaking across a telescope’s sightline.
But exactly how often this interference will happen remains to be seen. It all depends on where the satellites are above the Earth, the time of day, and the time of year. Satellites can be seen for a few hours around dusk and dawn when they catch the light from the Sun as the sky dims, but they won’t reflect light for many hours of the night whenever they are in the shadow of the Earth. However, in higher latitudes during the summer, satellites can be seen throughout the evening. That’s because they’re high enough in the sky to still catch the Sun and stay out of the Earth’s shadow. “You can go into your backyard with some binoculars or even the naked eye, and you can see plenty of satellites whizzing around a few hours past dusk or before dawn,” says Bull. “It’s really not like they just instantly switch off when the sun sets on Earth.”
For no reason at all, here's what it looks like when a satellite goes through Hubble's field of view whilst you are trying to image something in the distant solar system. pic.twitter.com/eLWR1ncdqx
— Alex Parker (@Alex_Parker) January 25, 2018
The problem is there is very little public data on how such giant constellations could pollute the night sky with light. There’s been a lot of discussion about how these mega constellations will potentially run into each other, causing debris that could pose a danger to other satellites in the sky. But the discussion of light pollution exploded over the weekend after amateur astronomers released footage of the Starlink satellites, showing them to be much brighter than people imagined. “There are plenty of us in the community that were aware of this concern, but until people saw with their own eyes this freight train of satellites, it didn’t really jump into the public consciousness,” Mary Knapp, a research scientist studying exoplanets at MIT Haystack Observatory, tells The Verge.
The Verge reached out to the Federal Communications Commission, which provided the license for Starlink, but we did not receive a response in time for publication. We also reached out to SpaceX twice but did not receive a response.
One astronomer, Cees Bassa, attempted to do the math and calculated just how many of these satellites might be visible in the sky at one time. For his analysis, he factored in the first leg of SpaceX’s Starlink constellation — about 1,600 satellites — as there are better details about the orbits they’re going to. Based on just that initial batch, he estimated that at a latitude of 52 degrees north (about where London is located), there will be 84 Starlink satellites above the horizon at all times. And for many hours around dusk, dawn, and in the nighttime during summer, 15 of those satellites would be visible in the sky at all times, about 30 degrees above the horizon.
Of course, that’s just the first batch of Starlink satellites; the impact of additional spacecraft could be worse. Bassa argues he didn’t go beyond the initial 1,600 in his calculations because he didn’t have accurate orbital data for the rest of the satellites — and their height affects their brightness. “If they’re higher, they’ll be fainter but visible for longer,” Bassa, an astronomer at the Netherlands Institute for Radio Astronomy, tells The Verge. “If the satellites are in lower orbits, they will be brighter but visible for less long.” Additionally, sometimes satellites can momentarily get brighter when they happen to catch the light from the Sun, causing more interference.
There are already 4900 satellites in orbit, which people notice ~0% of the time. Starlink won’t be seen by anyone unless looking very carefully & will have ~0% impact on advancements in astronomy. We need to move telelscopes to orbit anyway. Atmospheric attenuation is terrible. pic.twitter.com/OuWYfNmw0D
— Elon Musk (@elonmusk) May 27, 2019
Over the weekend, SpaceX CEO Elon Musk tried to downplay the astronomy community’s concerns, arguing that Starlink would have “~0% impact on advancements in astronomy.” He also claimed that the satellites would not be visible when the stars are out and that the reason the International Space Station is visible at night is because it’s big and has lights — two statements that aren’t true. (The ISS has very large solar panels that reflect lots of sunlight, even at nighttime on Earth.) Musk ultimately argued that “we need to move telescopes to orbit anyway” since these instruments have to deal with interference from Earth’s atmosphere.
That statement is naive, according to many astronomers. Telescopes can be built much bigger on Earth with dishes more than 30 meters (98 feet) in diameter, allowing astronomers to take in a lot of light and get more detailed observations. Launching such a massive telescope off of Earth is incredibly difficult, requiring giant rockets or very complex engineering. Right now, NASA is working toward launching its biggest space telescope yet, the James Webb Space Telescope, which has a primary mirror that’s a little more than 20 feet wide. Developing that telescope for launch and for space has taken decades, and the cost has ballooned to nearly $10 billion. “Taking these apertures off of the Earth and putting them in space is not technically feasible right now,” says Knapp. “And when and if it becomes so, it’s very, very expensive, much — much more expressive than the telescopes we have on the ground of similar size.”
In the end, even space-based telescopes in orbit around Earth still have problems with satellites. “We see satellites in space-based observations, too, when the satellites are above the space telescope,” says Knapp. “So it’s not just a ground-based observational problem.”
The good news is that the current batch of Starlink satellites are already getting dimmer, as they are slowly moving to their final higher orbits and spreading far apart. Many astronomers are eagerly waiting to see just how dim they become to better understand what the final effect of the Starlink constellation will be. After lots of backlash, Musk did say that SpaceX could tweak the orientation of these satellites to minimize any disturbance of astronomical observations, claiming that “we care a great deal about science.”
But it’s not just light that astronomers are worried about. Some are concerned that the radio frequencies these satellites will be transmitting on will also interfere with radio observations of the Universe. Often, astronomers will study radio waves coming from distant objects to learn more about them, especially hot bodies like stars that emit super intense X-rays that can be measured from Earth. Musk did say that SpaceX’s Starlink satellites won’t transmit at certain frequencies to avoid astronomy observations, but it could still create a blind spot. “As technology has progressed, the ability to look at the Universe at all frequencies has expanded greatly,” Colin Lonsdale, the director of the MIT Haystack Observatory, tells The Verge. “So what something like Starlink will do, it’ll shut off some of those frequencies from the possibility of study.” Lonsdale also argues that there is a possibility that there will be some level of transmission that spills outside the intended frequency bands.
Overall, Musk argues that providing global internet coverage is the “greater good” in the long run. Ultimately, many astronomers don’t want to stand in the way of this type of innovation, but many have also expressed interest in more data and discussions about the impact of the Starlink constellation on the night sky as well as other proposed internet satellite initiatives. “There’s been a long and very productive partnership between astronomers and the technology side of things to try and find solutions that work for everyone,” says Bull. “As far as I’m aware, that just hasn’t happened here. And to be honest, it’s unusual to have not consulted on this kind of impact.”
Once upon a time, humans couldn’t simply pop down to Tesco, buy a crab and then happily enjoy a lovely light lunch.
At some point in ancient history, our ancestors had to figure out how to catch fish and other aquatic organisms, potentially providing them with nutrients which powered the brain development process which led to the evolution of modern humans.
Now scientists have found a clue about how we might have started to harvest the sea’s bounty after spotting chimpanzees eating crabs for the first time.
Chimps living in the Nimba Mountains in Guinea, West Africa, have been observed eating freshwater crabs.
Females and young animals are most likely to catch a crab, which gives them the sort of nutrients they normally get from wolfing down handfuls of tasty ants.
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Tetsuro Matsuzawa, senior co-author on a paper detailing the discovery, said: ‘”This isn’t the first case of non-human primates eating crabs, but is the first evidence of apes other than humans doing so.
‘Notably, previous observations were from monkey species in locations consistent with aquatic faunivory – lakes, rivers, or coastlines — and not in closed rainforest.
‘It’s exciting to see a behaviour like this that allows us to improve our understanding of what drove our ancestors to diversify their diet.’
The research ‘sheds light on our own evolution’ because it suggests fishing might not be dependent on habitat – which means ancient humans may have caught creatures living in rivers as well as the sea.
‘The aquatic fauna our ancestors consumed likely provided essential long-chain polyunsaturated fatty acids, required for optimal brain growth and function,’ explained first author Kathelijne Koops from the University of Zurich and Kyoto University’s leading graduate program in Primatology and Wildlife Science.
‘Further, our findings suggest that aquatic fauna may have been a regular part of hominins’ diets and not just a seasonal fallback food.’
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A century ago, British astronomer Arthur Stanley Eddington and his colleagues photographed a solar eclipse, and changed the way humankind thought about the heavens.
Those photographs, taken on May 29, 1919, from Sobral, Brazil and Príncipe Island off Africa’s west coast, affirmed for the first time a key prediction of Albert Einstein’s general theory of relativity: Mass bends spacetime. The expeditions marked a revolution in physics and made Einstein a celebrity.
Today, physicists are at it again — on a much larger scale. In April, the Event Horizon Telescope (EHT) collaboration released the first picture of the edge of a black hole (SN: 4/27/19, p. 6). That image again showed that massive objects, such as black holes or the sun, can change how light travels, just as Einstein predicted.
“The EHT has done the exact same thing, but in the most extreme example imaginable,” says physicist and EHT team member Lia Medeiros of the University of Arizona in Tucson. “It’s almost poetic that these two experiments occurred almost exactly 100 years apart.”
So far, the new black hole data have confirmed general relativity. But future EHT images of the gravitational beasts — especially the one at the center of our own galaxy — could potentially poke holes in Einstein’s famous theory.
“Any time we have a theory that works so spectacularly, you just want to push it to its extremes,” says astrophysicist and EHT team member Michael Johnson of the Harvard-Smithsonian Center for Astrophysics. And black holes are “a laboratory of extremes — this is where we can point to new physics and point to cracks in our existing theories,” he says.
A hundred years ago, scientists didn’t have a black hole to test for cracks in general relativity —black holes were just the stuff of imagination back then — but they did have the 1919 total solar eclipse (SN Online: 4/12/19). At the time, the predominant theory of gravity was Newtonian, which says that gravity is a force. Forces can accelerate objects that have mass, but since light has no mass, gravity shouldn’t affect it, the thinking went. But a few years earlier, in 1915, Einstein had proposed his general theory of relativity, which says that gravity comes from matter and energy warping spacetime, generating curves that change objects’ motion or even the path of light itself.
In Eddington’s and his colleagues’ photographs of the eclipse, stars appeared in different positions in the sky during the eclipse, when their light had to pass the sun to reach earthly observers, than on an ordinary night (SN Online: 8/15/17). The sun’s gravity had changed the path that the starlight took. Einstein was right.
These days, the idea that gravity can curve light is so well understood that physicists use it to probe the properties of spacetime itself. Before the EHT started taking data in 2017, for example, scientists had used Einstein’s equations to get a precise idea of what a black hole should look like, if the theory didn’t break down in the extreme environment.
Black holes curve spacetime so extremely that light gets trapped inside them. So physicists can’t see light emitted by the black hole directly. But they can see the black hole’s shadow on bright material around it. Under general relativity, that shadow should have a specific size and shape: a circle whose width is directly related to its mass. “This all falls out of Einstein’s equations,” Johnson says. “If you have a different theory of gravity, you can predict a different ring on the sky.”
The EHT’s first picture captured the black hole in galaxy M87, about 55 million light-years from Earth, and looked like researchers thought it would. “Again, GR passes with flying colors, as far as we can tell currently,” Johnson says.
To take the image of M87’s black hole, astronomers linked up observatories around the world to make the Event Horizon Telescope, which is effectively the size of the entire Earth.
The theory’s next real test will come when the EHT team photographs the black hole in the center of the Milky Way, called Sagittarius A*. “The reason Sgr A* is in many ways a stronger test for relativity is we know very precisely exactly what that ring should look like, if [general relativity] really holds up,” Johnson says.
Sgr A* is close enough, about 26,000 light-years from Earth, that astronomers can see individual stars whipping around the black hole. That gives researchers an extremely accurate estimate of its mass, and thus the size of its shadow inside a glowing ring.
M87 is too far away for physicists to have measured its black hole’s mass precisely in advance of taking the picture. Previous mass estimates differed by a factor of two, and only the EHT measurement told scientists which mass was right (SN Online: 4/22/19). But that mass uncertainty meant that the prediction for the size of the ring was much weaker.
“There was a lot of wiggle room there” for M87, Johnson says. “For Sgr A*, there’s almost no wiggle room.” Either Sgr A*’s shadow is a certain width, or general relativity is broken.
Unfortunately, Sgr A* is a much more difficult black hole to photograph than M87. It’s about one one-thousandth the mass of M87. For perspective, that’s about 4 million times the mass of the sun compared to M87’s 6.5 billion times. That means that material swirls around Sgr A* much more quickly, making the black hole appear to flicker and vary over the course of a single night of observing.
But Medeiros and others on the EHT team are working on computer algorithms to work around that variability. It should take much less than another century to find out what Sgr A* has to say about general relativity.
It looked like a scene from a sci-fi blockbuster: an astronomer in the Netherlands captured footage of a train of brightly-lit SpaceX satellites ascending through the night sky this weekend, stunning space enthusiasts across the globe.
But the sight has also provoked an outcry among astronomers who say the constellation, which so far consists of 60 broadband-beaming satellites but could one day grow to as many as 12,000, may threaten our view of the cosmos and deal a blow to scientific discovery.
The launch was tracked around the world and it soon became clear that the satellites were visible to the naked eye: a new headache for researchers who already have to find workarounds to deal with objects cluttering their images of deep space.
"People were making extrapolations that if many of the satellites in these new mega-constellations had that kind of steady brightness, then in 20 years or less, for a good part the night anywhere in the world, the human eye would see more satellites than stars," Bill Keel, an astronomer at the University of Alabama, told AFP.
The satellites' brightness has since diminished as their orientation has stabilized and they have continued their ascent to their final orbit at an altitude of 550 kilometers (340 miles).
But that has not entirely allayed the concerns of scientists, who are worried about what happens next.
Elon Musk's SpaceX is just one of a several companies looking to enter the fledgling space internet sector.
To put that into context, there are currently 2,100 active satellites orbiting our planet, according to the Satellite Industry Association.
If another 12,000 are added by SpaceX alone, "it will be hundreds above the horizon at any given time," Jonathan McDowell of the Harvard Smithsonian Center for Astrophysics told AFP, adding that the problem would be exacerbated at certain times of the year and certain points in the night.
"So, it'll certainly be dramatic in the night sky if you're far away from the city and you have a nice, dark area; and it'll definitely cause problems for some kinds of professional astronomical observation."
Musk's puzzling response
The mercurial Musk responded to the debate on Twitter with contradictory messages, pledging to look into ways to reduce the satellites' reflectivity but also saying they would have "0% impact on advancements in astronomy" and that telescopes should be moved into space anyway.
He also argued the work of giving "billions of economically disadvantaged people" high-speed internet access through his network "is the greater good."
Keel said he was happy that Musk had offered to look at ways to reduce the reflectivity of future satellites, but questioned why the issue had not been addressed before.
If optical astronomers are concerned, then their radio astronomy colleagues, who rely on the electromagnetic waves emitted by celestial objects to examine phenomena such as the first image of the black hole discovered last month, are "in near despair," he added.
Satellite operators are notorious for not doing enough to shield their "side emissions," which can interfere with the observation bands that radio astronomers are looking out for.
"There's every reason to join our radio astronomy colleagues in calling for a 'before' response," said Keel.
"It's not just safeguarding our professional interests but, as far as possible, protecting the night sky for humanity."
© 2019 AFP
Citation: SpaceX satellites pose new headache for astronomers (2019, May 29) retrieved 29 May 2019 from https://phys.org/news/2019-05-spacex-satellites-pose-headache-astronomers.html
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