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.
Worldwide telescope
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.
In this screengrab taken from a video shot by Marco Langbroek, a group of SpaceX Starlink satellites passes over Leiden, Netherlands on May 24, 2019
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.
This screengrab taken from the SpaceX webcast transmission on May 23, 2019, shows a SpaceX Falcon 9 rocket with 60 Starlink satelites lifting off from Space Launch Complex 40 (SLC-40) at Cape Canaveral Air Force Station, Florida
"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."
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An exoplanet smaller than Neptune with its own atmosphere has been discovered in the Neptunian Desert around its star by an international collaboration of astronomers, with the University of Warwick taking a leading role.
The rogue planet was identified in the new research, led by Dr Richard West including Professor Peter Wheatley, Dr Daniel Bayliss and Dr James McCormac from the Astronomy and Astrophysics Group at the University of Warwick.
NGTS is situated at the European Southern Observatory's Paranal Observatory in the heart of the Atacama Desert, Chile. It is a collaboration between UK Universities Warwick, Leicester, Cambridge, and Queen's University Belfast, together with Observatoire de Genève, DLR Berlin and Universidad de Chile.
NGTS-4b, also nick-named 'The Forbidden Planet' by researchers, is a planet smaller than Neptune but three times the size of Earth.
It has a mass of 20 Earth masses, and a radius 20% smaller than Neptune, and is 1000 degrees Celsius. It orbits around the star in only 1.3 days -- the equivalent of Earth's orbit around the sun of one year.
It is the first exoplanet of its kind to have been found in the Neptunian Desert.
The Neptunian Desert is the region close to stars where no Neptune-sized planets are found. This area receives strong irradiation from the star, meaning the planets do not retain their gaseous atmosphere as they evaporate leaving just a rocky core. However NGTS-4b still has its atmosphere of gas.
When looking for new planets astronomers look for a dip in the light of a star -- this the planet orbiting it and blocking the light. Usually only dips of 1% and more are picked up by ground-based searches, but the NGTS telescopes can pick up a dip of just 0.2%
Researchers believe the planet may have moved into the Neptunian Desert recently, in the last one million years, or it was very big and the atmosphere is still evaporating.
Dr Richard West, from the Department of Physics at the University of Warwick comments:
"This planet must be tough -- it is right in the zone where we expected Neptune-sized planets could not survive. 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, and it was great to find after working on this project for a year.
"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."
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Materials provided by University of Warwick. Note: Content may be edited for style and length.
This article originally appeared in the May 20, 2019 issue of SpaceNews magazine.
Although NASA’s new goal of landing humans on the moon in five years may sound aggressive, most of the hardware needed to carry out that mission is already, or soon will be, under development.
The Space Launch System and Orion have been in the works for years and, despite delays, should be ready to transport astronauts to the moon by 2024. NASA is currently evaluating proposals for the first element of a now-minimized Gateway, the Power and Propulsion Element, and plans to award a contract by the summer. The only other element of that initial Gateway, a modest habitat and docking node, will likely be based on habitation module concepts several companies are currently developing.
The exception is the one component that is arguably the most essential part of a lunar landing: the lunar lander itself.
Jeff Bezos unveils a full-sized model of its Blue Moon lander May 9 at the Washington Convention center hours after the conclusion of the Satellite 2019 conference there. Credit: Blue Origin
Prior to Vice President Mike Pence’s March 26 speech announcing the 2024 lunar landing goal, NASA was slowly ramping up planning for crewed lunar landers. Earlier this year, NASA solicited proposals for studies of two lander elements, a descent stage and a transfer vehicle to move the lander from the Gateway to a low lunar orbit. Those proposals were due to NASA the day before Pence’s fateful speech.
NASA shifted gears after the speech, announcing a week later it would seek proposals for an ascent stage as well. In late April it changed its mind again: it now wanted proposals for entire lander systems — ascent stage, descent stage and transfer vehicle — with a formal solicitation expected by this summer. To meet the 2024 deadline, both the agency and industry say there’s no time to waste.
Two companies, two landers
Fortunately for NASA, there is a wide range of ideas of how to develop such landers — and how to unveil them. At one extreme was what Blue Origin did to show off its Blue Moon lunar lander. The company invited the media and other guests, from NASA officials and planetary scientists to Apollo 17 astronaut Harrison Schmitt, to a ballroom at the Washington Convention Center May 9, hours after the conclusion of the Satellite 2019 conference there.
Inside the ballroom was blue mood lighting, starscapes on the walls, and a stage with a curtain across it. On that stage soon appeared company founder Jeff Bezos, who spent a half-hour talking about his vision for humanity’s future in space along with the desire to build infrastructure to enable that vision, like the New Shepard and New Glenn launch vehicles.
“The moon also needs infrastructure,” he said. “Let me show you something.” The curtain rose, revealing a full-sized model of an updated version of the Blue Moon lander the company first discussed more than two years ago. In its current iteration, Blue Moon can carry 3.6 metric tons to the lunar surface using a new rocket engine called the BE-7 the company is developing, powered by liquid hydrogen and liquid oxygen.
Bezos narrated a tour of the mock-up, even using a crane-mounted camera to peer down on the top of the lander, a deck on which payloads would be mounted. He ticked off some of its technical specs, such as optical communications for gigabit data rates and terrain relative navigation for precise landings. “This is an incredible vehicle,” he said, “and it’s going to the moon.”
When Blue Origin first started discussing Blue Moon, they described it as a cargo lander only, and the version on display was designed for just that. However, the company also has a larger version of the lander with “stretched” propellant tanks capable of taking 6.5 tons of cargo to the surface. In his presentation, Bezos showed an illustration of an ascent stage on top of the lander for carrying astronauts. Another illustration featured that larger lander with an ascent stage on the moon, with astronauts walking on the surface nearby.
A company official, speaking on background after the event, confirmed that Blue Origin is planning to develop its own ascent stage for Blue Moon. The company foresees having the initial descent stage ready to fly in 2023, with the stretched version, along with the ascent stage, tested and ready to carry astronauts in 2024.
Bezos endorsed the 2024 deadline and suggested that it could meet it because of the head start it had on Blue Moon. “I love this. It’s the right thing to do,” he said of the 2024 goal announced in Pence’s speech. “We can help meet that timeline, but only because we started three years ago.”
This illustration is Lockheed Martin’s concept of a two-stage crewed lunar lander that NASA could use to go to the surface of the moon. The accent module is derived from the Orion spacecraft to ensure quicker development. Credit: Lockheed Martin
About a month before Bezos unveiled his full-sized Blue Moon mock-up, Lockheed Martin discussed its own concepts for lunar landers. In a small conference room at the 35th Space Symposium in Colorado Springs April 10, company officials, without the benefit of special guests or full-sized mockups, talked about how they planned to leverage Orion technology for a 2024 lunar lander.
The concept they presented was not their first lunar lander idea. Six months earlier, they described a giant single-stage reusable lunar lander that could carry four people and operate for two weeks on the surface. The rush to 2024, though, superseded that more ambitious design for a smaller two-stage lander that could be built quickly.
“We looked at what’s the fastest we could go,” said Tim Cichan, space exploration architect at Lockheed Martin, and concluded a two-stage lander could be ready by 2024. But, he added, “It’s going to be a challenge.”
The descent stage is based on concepts Lockheed Martin submitted to NASA in March in the call for proposals for descent stages, about which the company offered few details. The upper stage would make extensive use of elements of Orion, including the human-rated pressure vessel and a build-to-print version of the propulsion system for Orion’s service module.
The lander is part of an overall architecture very close to what NASA has since described for achieving the 2024 lunar landing, including the development of a minimal Gateway. The lander would be launched to the Gateway on commercial rockets, with the crew to follow on an SLS/Orion mission.
While Lockheed’s lander makes use of Orion technology, it still requires time to build. Based on the schedules for producing Orion capsules, Rob Chambers, director of human spaceflight strategy and business development at Lockheed Martin, noted it takes about four years from when the company starts production on an Orion spacecraft to when it’s ready for launch.
That means that work needs to start on the lander by early 2020 so it can launch to the Gateway in early 2024 to support a landing later in the year. “By the end of this year there needs to be materials starting to show up and folks on contract to begin building to print what exists today that we can safely leverage,” he said. “We need to be bending metal next year.”
How to buy a lunar lander
The accelerated goal for returning humans to the moon not only shapes how the landers will be designed but also how they will be acquired. Prior to Pence’s speech, NASA envisioned companies developing the three elements of the lander separately, with NASA overseeing the overall architecture and integrating the components.
“Initially we thought we’d keep it as three pieces and NASA would integrate them,” NASA human spaceflight chief Bill Gerstenmaier said at a town hall meeting at NASA Headquarters May 14. “Then we thought, nope, for speed it’s better that we let the commercial sector do that.” Credit: NASA/Joel Kowsky
With the new 2024 deadline, NASA plans to cede more control to industry. The revised solicitation for lunar landers will request integrated concepts, giving companies the flexibility to procure alternative approaches rather than NASA’s original three-stage lander concept.
“Initially we thought we’d keep it as three pieces and NASA would integrate them,” Bill Gerstenmaier, NASA associate administrator for human exploration and operations, said at a town hall meeting at NASA Headquarters May 14. “Then we thought, nope, for speed it’s better that we let the commercial sector do that.” Doing so, he added, gives companies the flexibility to come up with a design that meets NASA’s objectives and schedule.
NASA is also likely to depart from a conventional cost-plus contract for the lunar lander. “We would, in essence, be buying a service to take our astronauts from the Gateway down to the moon and back,” said NASA Administrator Jim Bridenstine at the town hall. “We’re looking to those service providers to create the absolute best ideas that they have.”
That town hall took place a day after the White House released its budget amendment for NASA, seeking $1.6 billion in additional funding for NASA in 2020. Of that total, $1 billion would go toward lunar lander development, specifically “an integrated commercial lunar lander.”
Gerstenmaier said at the town hall meeting he’d like to have the funding in place as soon as possible after the fiscal year starts Oct. 1 so “we can start laying in place the contracts that actually start building hardware that gives us a lander.”
That could be difficult, since NASA is likely to start the fiscal year on a continuing resolution (CR) that keeps the agency at 2019 funding levels and prevents the start of new programs. Bridenstine, speaking May 14 at the Humans to Mars Summit, said there may be “opportunities” to include language in any CR giving NASA the flexibility to start lunar lander and related projects. “But that goes well above my pay grade,” he added.
NASA announced May 16 that it selected 11 companies — including Blue Origin and Lockheed Martin — to design descent modules and transfer stages, based on the proposals those companies submitted back in March. The awards, for studies and prototype hardware, have a total value of only $45.5 million, with companies expected to contribute about 20 percent of the costs.
NASA Administrator Jim Bridenstine, speaking May 14 at the Humans to Mars Summit, said there may be “opportunities” to include language in a stop-gap spending bill giving NASA the flexibility to start lunar lander and related projects. “But that goes well above my pay grade,” he added. Credit: NASA/Aubrey Gemignani
NASA used the announcement to emphasize that buying lunar landers would not be business as usual. “To accelerate our return to the moon, we are challenging our traditional ways of doing business,” said Marshall Smith, director for human lunar exploration program at NASA Headquarters. “We will streamline everything from procurement to partnerships to hardware development and even operations.”
Testifying before the House Science Committee’s space subcommittee May 8, Gerstenmaier said the approach NASA uses for crewed landers may depend on how well companies do with smaller robotic landers through the Commercial Lunar Payload Services program.
“Depending on how well that works,” he said, “we can get a chance to judge how ready industry is to go take on the challenges of human-class landers.”
To meet the 2024 deadline, though, NASA may have no other option than to give industry that challenge of building the spacecraft that will land astronauts on the moon.
As helpful as SpaceX's Starlink satellites may be, they could be a pain for astronomers. The Harvard-Smithsonian Center's Jonathan McDowell and others have observed that the internet satellites are bright enough to cause a "problem" for astronomy, and the eventual constellation of roughly 12,000 satellites could complicate humanity's view of the night sky. It would triple the number of satellites in orbit, CNETnoted, forcing telescope operators to account for the objects.
The issue isn't as bad as initially feared, when the satellites hadn't finished orienting their solar panels and were thus extra bright (you can see a video of this below). The vehicles are only intended to last five years in orbit before descending to a fiery death in the atmosphere, for that matter, so this may only be a temporary issue. Elon Musk has maintained that the Starlink constellation "won't be seen by anyone" unless they're going out of their way to look.
Still, the executive was aware of the potential pitfalls and vowed to do something about it. SpaceX would ensure that Starlink "had no material effect" on astronomy, Musk said, adding that he'd asked the team to reduce the albedo (reflectivity) of the satellites going forward. He was even receptive to the idea of mounting telescopes on Starlink bodies to provide a clearer view of space. While these moves won't completely ease the minds of sky watchers, the company is at least aware of its potential impact in an era where a crowded orbit and space debris are very real issues.
How a barrage of lightning strikes triggered by ancient supernovae around EIGHT MILLION years ago could have first prompted human ancestors to walk upright
A supernova is the explosion of a star that has reached the end of its life
This cosmic energy initiated a surge of electrons in our lower atmosphere
Researchers say that this resulted in lightening strikes which caused forest fires
According to the team, the fires caused wide-expanses of open space which meant that ancient hominins didn't need to climb trees leading to their evolution
Published: 14:01 BST, 28 May 2019 | Updated: 14:17 BST, 28 May 2019
Supernovae that bombarded Earth with energy millions of years ago may have resulted in our ancient ancestors learning to walk upright, research suggests.
Electrons from the energy released from the exploding stars triggered a surge in lightning strikes, according to a new study.
These strikes sparked forest fires around the globe, with savannas arising to replace the scorched woodlands.
Prehistoric humans - or proto-humans - lived their lives on all fours in these forests before shifting to two to adapt to the new plains as far back as eight million years ago, experts say,
Exactly why and when our distant ancestors stood upright and started moving around on two feet is still widely debated by scientists.
This study, from the University of Kansas, claims that this was a knock-on effect from the supernovae.
These stars reached the end of their life and their energy reached Earth during the transition from the Pliocene Epoch to the Ice Age.
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A new paper from a University of Kansas researcher suggests bipedalism arose when ancient supernovae caused lightning that burned Earth's forests and prompted human ancestors to walk upright
Our planet was bombarded with cosmic energy starting as many as eight million years ago, with a peak some 2.6 million years ago.
This initiated an avalanche of electrons in the lower atmosphere. Atmospheric ionisation caused by waves of energy started lightning strikes that resulted in forest fires in northeast Africa.
The destroyed forests were then replaced by wide expanses of mixed woodland and open grassy plains.
This meant that our ancient hominin ancestors didn't need to climb trees and, because of this experts say, human evolution to walking upright on two legs took place.
Lead author Adrian Melott, a professor emeritus of physics & astronomy at the University of Kansas, even before this event,there was already a tendency for hominins to walk on two legs.
'But they were mainly adapted for climbing around in trees. After this conversion to savanna, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright.
'They could see over the tops of grass and watch for predators. It's thought this conversion to savanna contributed to bipedalism as it became more and more dominant in human ancestors.'
Based on a 'telltale' layer of iron-60 deposits lining the world's sea beds, astronomers have high confidence supernovae exploded near Earth during the transition from the Pliocene Epoch to the Ice Age.
Iron-60 is extremely rare on this planet with no known natural means to produce it, which leaves arrival from space as the logical origin.
The team calculated the ionisation of the atmosphere from cosmic rays which would come 'from a supernova about as far away as the iron-60 deposits indicate,' Professor Melott said.
Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons.
'Usually, you don't get lower-atmosphere ionisation because cosmic rays don't penetrate that far, but the more energetic ones from supernovae come right down to the surface - so there would be a lot of electrons being knocked out of the atmosphere,' he added.
As far back as eight million years ago, prehistoric humans, or proto humans, lived their lives on all fours before shifting to two. Exactly why and when our distant ancestors stood upright and started moving around on two feet is still widely debated. Here, artist's impression
Ionisation in the lower atmosphere meant an abundance of electrons would form more pathways for lightning strikes, according to Professor Melott.
'When high-energy cosmic rays hit atoms and molecules in the atmosphere, they knock electrons out of them - so these electrons are running around loose instead of bound to atoms,' he added.
Lightning occurs when there's a buildup of voltage between clouds or the clouds and the ground.
The current can't flow because not enough electrons are around to carry it so it has to build up high voltage before electrons start moving.
These knock more electrons out of more atoms and it builds to a lightning bolt.
But with ionisation that process can get started a lot more easily, resulting in far more lightning bolts.
WHAT IS A SUPERNOVA AND HOW DOES IT FORM?
A supernova occurs when a star explodes, shooting debris and particles into space.
A supernova burns for only a short period of time, but it can tell scientists a lot about how the universe began.
One kind of supernova has shown scientists that we live in an expanding universe, one that is growing at an ever increasing rate.
Scientists have also determined that supernovas play a key role in distributing elements throughout the universe.
In 1987, astronomers spotted a ‘titanic supernova’ in a nearby galaxy blazing with the power of over 100 million suns (pictured)
There are two known types of supernova.
The first type occurs in binary star systems when one of the two stars, a carbon-oxygen white dwarf, steals matter from its companion star.
Eventually, the white dwarf accumulates too much matter, causing the star to explode, resulting in a supernova.
The second type of supernova occurs at the end of a single star's lifetime.
As the star runs out of nuclear fuel, some of its mass flows into its core.
Eventually, the core is so heavy it can't stand its own gravitational force and the core collapses, resulting in another giant explosion.
Many elements found on Earth are made in the core of stars and these elements travel on to form new stars, planets and everything else in the universe.
The probability of a lightning spike kicking off an upsurge in wildfires is supported by the discovery of carbon deposits found in soils.
Researchers found that these soils corresponded with the timing of the cosmic-ray bombardment, lending more credence to their theory.
The observation is that there's a lot more charcoal and soot in the world starting a few million years ago,' Professor Melott said.
'It's all over the place, and nobody has any explanation for why it would have happened all over the world in different climate zones.
No such event is likely to occur again anytime soon.
The nearest star capable of exploding into a supernova in the next million years is Betelgeuse, some 652 light years from Earth.
SpaceX has created a brand new website dedicated to its Starlink satellite constellation, a prelude to offering Internet service to consumers after as few as six launches.
Additionally, Starlink.com reiterated CEO Elon Musk’s estimate that SpaceX will conduct 2-6 dedicated Starlink launches – carrying at least 60 satellites each – in 2019 alone. In other words, a best-case satellite deployment scenario could mean that SpaceX will be able to start offering Starlink service to consumers “in the Northern U.S. and Canadian latitudes” as early as this year, while commercial offerings would thus be all but guaranteed in 2020. A step further, SpaceX believes it will be able to offer coverage of the entirety of the populated world after as few as 24 launches (~1500 Starlink satellites).
“Starlink is targeted to offer service in the Northern U.S. and Canadian latitudes after six launches, rapidly expanding to global coverage of the populated world after an expected 24 launches. SpaceX is targeting two to six Starlink launches by the end of this year.” — SpaceX, Starlink.com
This quiet announcement of SpaceX’s expected initial operational capability (IOC) confirms that the company’s plans to offer communications services to consumers are just as ambitious as its 60-satellite, 18.5 ton (~40,000 lb) Starlink launch debut. Assuming an average of 60 Starlink satellites per launch, SpaceX wants to begin serving customers in the US and Canada as soon as ~360 spacecraft are in orbit, a milestone that could occur as early as late 2019. Sometime in the first half of 2020 is arguably far more likely, but the fact alone that service could be offered in 2019 illustrates just how far SpaceX is ahead of its competitors, of which only OneWeb seems to pose an actual threat.
On February 27th, OneWeb launched its first six satellites – down from a planned ten, already ~20 satellites short of a ‘full’ launch – as a mix between its first orbital test and the first launch of operational spacecraft. OneWeb’s initial constellation will feature 648 satellites, potentially rising to 900 and eventually ~2000 in the years to come, pending commercial success and investor interest. The company currently has plans to begin a monthly launch campaign of ~20 Soyuz rockets no earlier than than August or September 2019, likely completing the first phase of its constellation sometime in 2021.
“OneWeb and its satellite manufacturing partner Airbus Defence and Space have crammed 10 gigabits per second of capacity into spacecraft the size of dishwashers. Tom Enders, Airbus Group’s outgoing CEO, said Feb. 14 that OneWeb satellites cost $1 million each to produce, and that the companies will be able to complete 350 to 400 satellites annually from their joint venture OneWeb Satellite’s $85 million Florida factory opening in April. The first batches of Florida-built satellites should be delivered to OneWeb toward the end of the third quarter, Airbus spokesman Guilhem Boltz said.”
Assuming SpaceX aims to launch one dedicated 60-satellite Starlink mission every 6-8 weeks, the company could easily have a constellation of more than 600 satellites in orbit by the end of 2020. Compared to OneWeb, each Starlink satellite weighs about 40% more (~150 kg vs. ~230 kg) but also offers almost double the usable throughput (~17-20 Gbps vs. OneWeb’s ~10 Gbps). In short, SpaceX should be able to offer the same capacity of coverage and service as soon – if not far sooner – than OneWeb, while constellation hopefuls like Telesat, LeoSat, and Amazon’s Project Kuiper are likely 2-5 years away from launching their first satellites, let alone offering service.
Starlink satellites deploy their solar arrays in this official visualization. (SpaceX)
SpaceX’s foray into satellite design
Aside from revealing SpaceX’s tentative schedule for its Starlink service offerings, Starlink.com included excellent, surprisingly detailed renders of satellite hardware, ranging from Dragon-heritage star trackers to the world’s first flightworthy ion thrusters powered by krypton. These renders simply confirm what was already clear: SpaceX has gone against the grain of traditional satellite design at almost every turn, producing a bus (the general structure and form factor) that is unlike almost anything that came before it.
A general overview of Starlink’s bus, launch stacking, and solar array. (SpaceX)Starlink’s star trackers (left; used for precise pointing and positioning) and what are likely four gyros, also used for pointing and orientation. (SpaceX)One of Starlink’s krypton ion thrusters is tested at SpaceX’s satellite production facilities. (SpaceX)
As a complete layperson to spacecraft design, it’s hard to describe SpaceX’s first internally designed satellite bus as anything less than elegant. Thanks to their uniquely flat form factor, the satellites can be packed into a Falcon 9 fairing with extreme efficiency, making SpaceX’s first dedicated Starlink launch the company’s heaviest payload ever at more than 18.5 tons (~40,000 lb). For comparison, OneWeb plans to launch approximately 30×150 kg satellites per Soyuz 2.1 launch with a traditional cylindrical adapter, itself weighing ~1000 kg.
For Starlink, the method the 60 satellites use to securely attach to each other remains a minor mystery, only hinted at by photos and renders that show three metal rings/connectors per satellite. However it works, it appears that SpaceX has found a way to launch and deploy dozens of fairly large spacecraft while wasting little to no mass on a dedicated dispenser. Altogether, it appears that SpaceX has already begun to surpass the technological capabilities of its competitors, while also taking large risks with highly innovative, largely unprecedented design choices. All of those characteristics will help as SpaceX pushes to deploy Starlink and begin serving customers as quickly as possible.
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SpaceX wants to offer Starlink internet to consumers after just six launches
