The Week in Space and Physics
On superflares, Proxima Centauri and Earth, Starlink and OneWeb, and the dawn of orbital space tourism.
Five years ago astronomers confirmed the presence of an Earth-sized planet around Proxima Centauri, the closest star to our own solar system. Interestingly, the planet, named Proxima Centauri B, orbits in a sweet spot: making it warm enough to have oceans of water and possibly a thin atmosphere. That, excited scientists proclaimed, means it could have life.
Unfortunately, the planet is almost certainly dead. Proxima Centauri is a flare star, a type of small but violently active star. Several times a year, Proxima Centauri unleashes a wave of fury on its planets, sending clouds of energetic plasma cascading across its solar system.
Though our Sun occasionally does the same - one such flare was seen in 2012, and another in 1859 - they are rare and weak enough for our planet to pass through almost unscathed. The Earth is surrounded by a magnetic field, one that deflects many of the energetic particles coming from the Sun. Big solar flares may cause dramatic aurora across the planet, but they are not a major threat to life.
The story for Proxima Centauri is rather different. The star is much smaller than our own - it is a red dwarf star, just a fifth of the size of the Sun. It burns at a much cooler temperature, and shines with a more feeble light. The planet, Proxima Centuari B, orbits much closer to it than we do to the Sun.
Though that makes it similar, temperature-wise, to the Earth, it also means it is subject to the whims of Proxima Centauri. The planet is probably bathed in a constant stream of radiation pouring from the star, a wind that should have long ago stripped away any protective layers in its atmosphere.
It is the flares, however, that astronomers suspect provide a knockout punch. Some are incredibly powerful - dozens of times stronger than anything the Sun gives out. Indeed, one flare we spotted in 2019 was the strongest ever seen, not just on Proxima Centauri, but almost anywhere in the galaxy.
That flare was seen during an intense observation campaign of the star, one supported by nine different telescopes around the world, including the Hubble Space Telescope. Over many months astronomers took repeated measurements of the star - and spotted several big flares erupting from its surface.
The biggest was seen in May 2019, and lasted just a few seconds. It was unbelievably powerful - as seen in ultraviolet light, the star brightened by 14,000 times. That, despite the small size of Proxima Centauri, is perhaps a hundred times more energy than anything our own star has ever thrown out.
For Proxima Centauri B, such events may be frequent. And for any life that happens to form there - or any colonists we may one day send - they are almost certainly devastating. Hopes for life around our closest stellar neighbour, then, look dim.
Superflares on Earth?
The Sun, fortunately, seems much more stable than Proxima Centauri. Though our star has been known to emit big flares, these events happen rarely; perhaps once a century or less. That is good news for life on Earth, certainly.
Even so, big flares are a danger for technological civilization. Energetic particles can knock out satellites and threaten the lives of astronauts. Wild magnetic fluctuations wreck havoc on electrical grids; potentially disrupting power grids and even the Internet.
Just like the recent pandemic, big solar flares are both rare and high impact events. They can strike almost without warning - perhaps two or three days, at best - and inflict tremendous consequences on society. In the worst case scenario a flare could leave a continent without electricity for months, take down the Internet and wipe data from millions of hard drives.
Scientists have struggled to work out just how likely such a scenario is. Powerful flares seem to be rare - in two centuries of observations only two events have been seen that could have serious effects on civilizations. But hints from the deep past, and from other solar systems, seem to indicate that superflares - flares far stronger than we’ve ever seen - could be more common than we think.
The first evidence comes from observations of other sunlike stars, scattered around our galaxy. Measurements show that they sometimes brighten briefly, evidence of a dramatic flare erupting from their surface. Astronomers are uncertain, however, exactly how these superflares occur, and whether our Sun is even capable of creating one.
To find out, astronomers need better measurements of the Sun’s history. One option is to turn to ancient tree trunks, as Fusa Miyake, a Japanese researcher, has done. When a big flare hits the Earth, it tends to create certain chemicals in the atmosphere; chemicals that end up being absorbed by trees and plants. Traces of these chemicals are thus recorded in tree trunks, helping to form a history of the Sun’s activity over millennia.
Analysis of these trunks showed evidence of two big events - one in 774AD, and another, probably, in 994AD. The event in 774 seems to have been enormous - the trace it left indicates a flare dozens of times bigger than any seen in the last two centuries. Should something similar strike today, the effects on civilization would be devastating.
With only one sample, however, researchers had no way of knowing how frequent such events are. Do they happen once every millennium? Or perhaps just once in a hundred thousand years? To find out, researchers recently delved deeper into the past; looking back twelve thousand years.
Their study revealed two other events on the scale of 774 - ones dated impressively accurately to 7176 BC and 5259 BC. In one way this is reassuring - superflares seem relatively rare, occurring once every few thousand years. Even so, we now know that they can happen - and the impact, when one does, threatens to be devastating.
OneWeb and Starlink
Both Starlink and OneWeb recently reached major milestones in the deployment of their large satellite Internet constellations. OneWeb, the smaller of the two constellations, now has over three hundred satellites in orbit, roughly half of the six hundred they plan to put up. Starlink, by contrast, has almost 1800 satellites, enough to start putting a second “shell” in orbit.
Almost all Starlink satellites have so far been placed in orbits taking them over 53 degrees of latitude - meaning the company can offer service as far north as the southern tip of Alaska. The second shell, by contrast, will use orbits reaching 77 degrees of latitude - enough to provide service to northern areas of Canada and Europe.
Starlink’s newest satellites finally include laser links, an innovation that will allow the satellites to beam data through the constellation. That will, in principle, allow more efficient routing of internet traffic entirely through space, with only the end points lying on Earth.
Laser communication in space is an interesting technology; potentially allowing extremely high data rates. It is, however, challenging to implement in practice. Laser beams must be able to find and track fast moving satellites, and must remain stable enough for a link to form. Designing algorithms to efficiently move data through such a rapidly changing network is also no easy feat.
Even without the laser links, Starlink have been offering satellite service, in a public beta at least, for several months. Though the service has not been without its problems, Elon Musk is apparently satisfied enough to announce that Starlink will emerge from the beta campaign within a month.
OneWeb, by contrast, expect to start commercial services at the end of this year, and already have global - including the polar regions - coverage. Next year, then, is likely to see the real test of whether satellite internet can live up to its enormous hype.
Inspiration4
In a major milestone, SpaceX successfully launched a crew of four amateur astronauts into orbit. The mission, Inspiration4, spent three days circling the Earth, flying higher than the International Space Station, before returning on Saturday afternoon.
This is, for the first time in history, a fully commercial orbital flight. The rocket and capsule were built and developed by SpaceX, and then charted by Jared Isaacman, an American billionaire. The crew, selected by him, have had only a short period of training - far less than the traditional NASA astronaut would experience.
With four astronauts aboard Inspiration4, seven on the International Space Station, and three taikonauts on the Chinese Tianhe station, there were briefly fourteen men and women circling our planet. That is the most since the dawn of the space age.
For now, however, the mission is a one off. Neither Isaacman or Musk have announced additional private orbital flights - although SpaceX have already signed contracts to carry a private crew to the International Space Station next year, and around the Moon in 2023.
Even so, the mission is a big step forward, and perhaps a first look at the future of human spaceflight. With SpaceX finally offering the chance to fly astronauts into space to anyone who can afford to pay, we may be on the verge of an exciting period of innovation and commercial activity in human spaceflight.
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"When a big flare hits the Earth, it tends to create certain chemicals in the atmosphere; chemicals that end up being absorbed by trees and plants." WOW! :)