The Week in Space and Physics: What Comes After The Space Station?
The Week in Space and Physics: What Comes After The Space Station?
On the future of space stations, a mysterious cosmic ray, a reanimating stellar corpse and a sand strewn exoplanet
On November 20 the International Space Station celebrated its twenty-fifth birthday, marking the anniversary of when Zarya, its first module, lifted off from Kazakhstan in 1998. The station itself started to take shape a few weeks later, when its second module - the American-made Unity - arrived onboard the Space Shuttle. Astronauts would not move in until November 2000 - but ever since they have maintained an unbroken presence, now in its twenty-fourth year.
How much longer it can last, however, is up for debate. Officially the station is slated to keep operating until 2030, and possibly longer if the nations running it can agree. Yet at the same time the overall condition of the station is deteriorating. Leaks in some of the modules mean the station is constantly losing air into the vacuum of space. Equipment is beginning to break down and, in the more complex cases, is not always reparable.
Whenever the end does come, its owners will face two challenges. First, they’ll need to find a way to get rid of it. The station orbits four hundred kilometres up, low enough to still feel the effects of atmospheric drag. At the moment rockets periodically boost its altitude, compensating for this. Yet after the astronauts leave it will make little sense to keep boosting it.
Leaving the station to fall back to Earth is, however, dangerous. It is large enough to survive a plunge through the atmosphere and, in a worst case scenario, could spread debris over several countries. Instead NASA is looking at building a special spacecraft to bring it down safely, a mission the agency says will cost a billion dollars to complete.
Second, however, is the question of what comes next. The International Space Station has served as a useful destination for visitors from America, Europe and Russia. After it is gone, where will those astronauts go? One option is the Chinese space station, which seems likely to attract visitors from Russia and possibly Europe. But NASA is banned from working with China, and it is unlikely, anyway, that American politicians could stomach sending astronauts to a Chinese station.
There is a risk, NASA has warned, of a “space station gap”, a period of time in which America has no sustained presence in Earth orbit. One option, which the agency is actively exploring, is to sponsor private companies to build stations. Axiom, an American company, has plans for one, as does a venture formed between Voyager Space and Airbus.
Yet last week NASA seemed to accept that these stations are unlikely to be ready by 2030. That result would be a space station gap lasting at least a few years, during which time NASA may have to face the embarrassment of seeing China operating in a terrain they have long considered their own.
In the longer term, however, the prospects for American and European activities in orbit and beyond look bright. Even if a space station gap does last for a few years, the two continents are still working together to send astronauts to the Moon. Commercial options, even if they progress slower than hoped, look bright. And, of course, there is the prospect of Starship, with all the power it promises, shining on the horizon.
A Bolt From the Void
A powerful cosmic ray smashed into the Earth back in 2021, according to a report published last week. The ray was one of the most energetic ever detected, and certainly the strongest seen in the past three decades. Mysteriously, however, it seems to have come from a region of empty space with no obvious origin for such an energetic visitor.
Most cosmic rays are high-energy particles, boosted to huge speeds by violent cosmic events like supernovae. Thousands of them hit the Earth every second. Most do so with an energy of around three hundred million electron-volts, or a tiny fraction of a Joule each. The 2021 ray, however, carried more than two hundred quintillion electron volts - equal to about forty Joules.
To put that in context, the particle - of subatomic scale, remember - carried as much energy as a baseball moving at fifty miles per hour. That is about twenty million times more energetic than the particles made by the Large Hadron Collider, the most powerful particle accelerator on Earth.
So unusual was this ray that when it was first spotted, at a cosmic ray detector in Utah, physicists assumed there must have been a mistake. Yet the evidence checked out, and the ray seems to have been real. When they traced back its path, however, they found no clear origin for such an energetic particle.
It seems to have come from a vast void in space, within which few galaxies exist. Certainly nothing is there that could have created a particle of such high energy. One possibility is they made a mistake. The ray has likely bounced off the Milky Way’s magnetic field, though even when this is taken into account there is still no obvious origin.
That has left physicists speculating of a more exotic possibility. In the paper reporting the ray, the authors suggest that an incomplete knowledge of particle physics may be to blame. The particle, in other words, may be a hint that more is going on than we know, and that our current theories of physics are inadequate to explain it.
The Strange Afterlife of a Dead Star
In September last year, telescopes picked up a flash of light coming from a distant galaxy. It seemed to be powerful, far stronger than a supernova; but was brief, fading away within a few days. Later, as astronomers studied the event in detail, they realised it was flaring up again and again; creating short bursts of intense light.
A handful of other events like this have been spotted over the past few years but none, so far, has a clear explanation. In a paper covering last September’s event, researchers concluded that it came from an object no bigger than ten times the width of the Sun. That points to a large star as the probable culprit.
Most likely, they say, something happened to that star - either a sudden collapse, similar to those that trigger a supernova; or an encounter with a black hole. That probably caused the initial flash of light seen in September, and resulted in an ultradense corpse - either a neutron star or a black hole.
The subsequent flashes of energy are probably coming from debris swirling around that corpse. One possibility is that it has a powerful magnetic field, through which streams of particles are moving. That could generate strong jets of energy which, from Earth, would appear as brief bursts of light.
Still, the evidence to support this idea is still not strong. Other explanations are possible, including that we are seeing a star slowly ripped apart by a black hole. More observations will be needed to settle the question for sure.
Sandstorms on WASP-107b
In 2017 astronomers discovered an odd planet some two hundred light years away that they named WASP-107b. Though it appears to have a similar size to Jupiter, it seems to weigh far less - which, its discoverers realised, makes it one of the least dense planets known.
A recent study of the planet by the James Webb telescope, as reported in Nature, found an interesting mix of chemicals in its atmosphere. The telescope saw signs of both water vapour and silicon dioxide - sand, essentially - swirling around the planet. These probably form high altitude clouds, traces of which were also picked up by the James Webb.
Since WASP-107b is extremely hot - it lies closer to its star than Mercury does to ours - the sand clouds can only form high up in its atmosphere. The study reckons, however, that sand is then raining out of those clouds, falling into the planet’s boiling interior. There, heated to thousands of degrees, it is vaporising and rising until it once again cools enough to form clouds.