The Week in Space and Physics
On bizarre supernovas, the risks to the space station, and a bad week for the rocket industry
Our Sun is destined to die a quiet death. At first, billions of years from now, the signs will be hard to spot. A gradual cooling, a slow expansion, perhaps, as its nuclear fuel starts to run short. But before long the signs will become all too obvious, to the peril of anyone who still lives on Earth.
Its outer layers will expand, until they consume the inner planets. Its colour will fade, turning from vivid yellow to a dull red. As the Sun weakens, those outer layers will be swept away into space, until only a cold, hard core remains. That - a white dwarf star - will stick around until the end of time, an eternal tombstone to our life-giving Sun.
Most stars in the night sky will one day meet a similarly slow and calm end. But some, the giants of the galaxy, are fated for a more dramatic finale. When a supermassive star dies - one several dozen times bigger than our Sun - the result is a dramatic and intense explosion. Much of the star is blown out into space at tremendous speed. What remains collapses into an ultra dense object - either a black hole or a neutron star.
Such explosions - supernovae - are incredibly powerful. For a few brief moments a dying star can shine brighter than a hundred million stars combined, outshining an entire galaxy. Though such events are rare - one happens in our own galaxy no more than twice per century - the cosmos is large enough for us to spot hundreds each year.
So when, in 2017, astronomers saw a powerful flash of radio waves coming from a distant galaxy, a supernova was a natural explanation. Indeed, such an event might have passed unnoticed. Such flashes are often seen and recorded, but rarely investigated in detail. Astronomers often chalk them down as supernova or colliding neutron stars, and then move on to more pressing matters.
But this flash, as it turned out, was intensely bright, one of the brightest such radio flares ever seen. That spiked the interest of a researcher at Caltech, Dillon Dong, who decided to take a closer look. He found something odd - the source was, he thinks, a star surrounded by a thick cloud of gas, a rather unusual cosmic object.
The radio flash was indeed a supernova - the star had blown up, sending debris smashing through the cloud of gas. But more intriguing was another matching signal: an X-ray blast emitted a few years earlier from the same object. That X-ray signal was intense and rather unusual; far shorter than other, similar, X-ray flares.
Together the two signals betray an unusual series of events. The researchers think that the object was once a system of two stars locked in orbit. Such systems are not unusual - millions are known in our own galaxy. At some point, however, one of the two stars died, collapsing into a black hole or possibly a neutron star.
That object - black hole or neutron star - started sucking up the outer layers of its companion star, forming, over several centuries, a thick cloud of gas. That created the unusual object Dong saw, but it also caused the black hole to spiral inwards towards the star - and eventually into the star itself.
The result - a merger of a black hole and star - was catastrophic. The black hole likely ended up somewhere near the centre of the star, disrupting the nuclear reactions that the star relies on. Deprived of stability, the star collapsed and then exploded - forming the supernova and X-ray burst. The radio blast followed soon after, when debris from the exploding star smashed into the thick gas cloud left behind by the black hole.
That scenario, if true, highlights the varied ways in which cosmic objects can interact. Astronomers have long speculated about the fates of binary systems, but evidence of such unusual supernova is rarely seen. It also, since the discovery of the accompanying X-ray signal came only by chance, shows how limited our view of the universe still is.
Without the fortunate combination of signals, seen by different telescopes - one on Earth, one on the International Space Station - uncovering the story behind this particular radio burst would have been impossible. Undoubtedly many other fascinating stories are hiding in our astronomical data, if only we could spot them.
A Space Station in Peril?
Nearly a quarter of a century after construction in orbit began, engineers are warning the International Space Station may soon face disaster. At blame are aging components on Russian modules, especially the Zvezda module, which provide crucial life support infrastructure.
Over the past few months, astronauts and mission controllers have noticed persistent air leaks from the space station. They were slow - so astronauts were not in danger - but the cause seems to have been small cracks developing in the shell of some of the older modules. That is a worrying sign. Though the cracks have been patched, and the leaks stopped, engineers think that they could soon fracture further.
What’s worse, much of the machinery providing life support is far beyond its designed lifespan. Though breakdowns are common - a few months ago cosmonauts repaired an oxygen generator - the fear is that a more permanent failure will soon occur.
That probably wouldn’t mean immediate catastrophe. The station has supplies to last several weeks, and crucial systems often have backups. But getting replacement equipment up to the station and installed quickly enough can be challenging. That could mean controllers send astronauts back home earlier than planned, or even abandon the station temporarily.
Though the station has been inhabited for over twenty years, it came close to such a temporary abandonment in 2018. On that occasion rockets were to blame: after a Soyuz launch went dramatically wrong, human flights to the station were suspended for months. With no way to send astronauts into orbit, controllers feared that they would be forced to leave the station empty.
Fortunately the Soyuz returned to flight before that became inevitable. Today such a scenario is far more unlikely - with SpaceX’s Dragon capsule, the world now has two human rated spaceflight systems. Still, the risk of equipment failure remains, and continues to grow as crucial infrastructure grows older.
Many of the most vital systems are found in Russia modules. And though Russia has committed to support the International Space Station for the next few years, it has often spoken about pulling out in 2025. In truth that seems unlikely. Russia cannot afford to build its own station, and would be reluctant to give up the prestige of having cosmonauts onboard.
Instead we will probably see Russia staying with the space station, but pushing the repairs - which it perhaps cannot afford either - onto other partners. One strong sign that they intend to stick around is Nauka, the first new - and Russian - module to be attached to the station in years.
After a dicey start - laced with propulsion and software issues - Russian cosmonauts have finally started integrating that module with the rest of the station. It would seem odd to abandon it after just a few more years.
The Rocket Industry Stumbles
It was an interesting week for the horde of startups vying to build a new generation of rockets. Two American companies - Astra and Firefly - launched spectacular test flights, neither of which made it to orbit. Meanwhile, oxygen shortages delayed a series of SpaceX flights, and NASA pushed the maiden launch of the SLS out to 2022.
Those last two issues are, at least officially, caused by resurging coronavirus cases across the United States. As medical demands for oxygen have increased, SpaceX has found it increasingly hard to get hold of the liquid oxygen needed to fuel its rockets. That, along with shipping delays caused by the pandemic, may be one reason for the recent pause in Starlink launches - though SpaceX also say this is down to upgrades to the new Starlink satellites themselves.
Progress on preparing the SLS for launch, meanwhile, is going more slowly than expected. That may indeed be down to coronavirus delays, but experience tells that the pandemic is often an excuse for other issues.
Over the next few weeks engineers will stack and roll out the giant rocket, after which it will undergo a rehearsal launch. That should take place by the end of the year. The rocket will then return to the hanger for final checks for launch. If all goes to plan, Ars Technica report that could now take place in spring 2022, though any more issues will likely mean a delay until at least the summer.
As for Firefly and Astra, both companies saw hopes for successful test launches go up in flames this week. Astra’s rocket displayed an interesting “sideways” launch, as an engine failure meant it lacked the power to do more than hover above the ground. The rocket did eventually head skyward, only for controllers to terminate the flight over the Pacific Ocean.
Firefly’s rocket, meanwhile, dramatically exploded roughly two minutes after liftoff. The cause remains unknown; though tracking data suggests the rocket failed to fly as fast as expected. That likely indicates a problem with the rockets engines.
Both Astra and Firefly are entrants to a crowded field. In recent years rockets have attracted billions of dollars of funding, as investors seek to replicate the success of SpaceX. That may be easier said than done. Despite a rapid increase in the number of satellites being launched each year, evidence suggests that the number of launches is remaining fairly static.
That’s because launch providers are cramming more satellites into each rocket. One recent SpaceX flight carried more than one hundred small satellites into orbit - a trend that seems destined to continue.
Instead of an explosion in demand for rockets, then, the market actually seems to be pushing towards fewer, but bigger, launches. That might be good news for SpaceX, but devastating for the likes of Astra and Firefly.
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I really love this newsletter. The writing is excellent and the subject matter fascinating! The supernova story was a perfect addition to my first cup this morning. Thank you for writing and sharing this information!