The Week in Space and Physics: The Sun and Superflares

On solar superflares, Betelgeuse's companion, the expanding universe, and the future of Artemis.

The Moon rises over the Earth’s horizon, as seen from the International Space Station. Image credit: NASA Johnson.

In the year 993 AD an unusually strong solar flare hit the Earth. Few people at the time seem to have noticed it, and only a scattering of records hint at the dramatic aurora that must have appeared that night. Yet we know it happened because the trees have told us: hidden in their rings is a spike in carbon 14, an atom created in the upper atmosphere under the bombardment of solar particles.

Around a millennium later, in 1960, the remains of some wood frame houses were found in Newfoundland near a village called L'Anse aux Meadows. In design they matched the structures of the Vikings, which was strange, since the Vikings lived in Scandinavia in the eleventh century and no European was supposed to have set foot in the Americas until 1492.

Half a century after that, analysis of the wood from that site found something remarkable. The flare of 993 was visible within them, recorded in the carbon 14 levels of their tree rings. Twenty-eight years after that flare, some men from Scandinavia arrived, cut the trees down and built them into houses. Vikings, in other words, were present in North America in 1021 AD.

All this is a long way of telling you that tree rings can tell us much about the past. The history of the Sun, indeed, is written within them, and has been traced back over ten thousand years. Thanks to this record we know that big solar flares have struck the Earth at irregular intervals over the past ten millennia.

Many of these flares seem to be far bigger than anything modern science has seen. That’s worrying, especially as such a huge flare would not pass unnoticed today. Solar flares can wreak havoc on electrical grids and systems, take down satellite networks and put astronauts in grave peril. A bigger one, like that of 993, could be catastrophic.

The question, then, is how often these flares happen, and thus how much danger we might be in. The tree ring record, interesting as it is, is not detailed or long enough to answer this question. Instead astronomers have turned to the skies, as they are wont to do, and studied thousands of other Sunlike stars scattered across the galaxy.

In one recent paper, researchers reported examining data from more than fifty thousand such stars. Seen among them, over four years of data, were more than two thousand “superflares”, any of which could match the power of 993’s event. This, the study authors say, suggests stars like our Sun emit such a superflare about once per century on average.

That might be taken as a warning, especially as the Sun does not seem to have given out such a superflare in the recent past. But these are probably also random events, and so we have no real way of saying we are “overdue” for one or not. Still, the study does tell us big flares are possible. Like pandemics or earthquakes, these are rare events with enormous impacts. We should make sure we are prepared.

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Does Betelgeuse Have a Companion?

For decades Betelgeuse has been one of the most closely watched stars in the night sky. It is, after all, the closest red supergiant to Earth, and thus the most likely to produce a dazzling supernova in the near future. When it does, at some point in the next few millennia, it will shine as bright as the full moon for weeks on end.

It may seem odd, then, that scientists are unsure about whether Betelgeuse is really one star or two. On the one hand, direct observations of the star have found no signs of a second star there, and telescopes have been able to photograph the surface of Betelgeuse, proving that it really is a red supergiant. At the same time, however, various pieces of indirect evidence hint at the presence of a small unseen star moving around it.

At the end of November, a paper published in The Astrophysical Journal studied a regular fluctuation in the brightness of Betelgeuse. This seems to follow a pattern that repeats every six years or so. So too, they say, does a pattern in how it moves backwards and forwards, as seen from Earth.

They think these two patterns suggest a second star, one slightly bigger than the Sun, is orbiting close to Betelgeuse. Such a star, they note, would be impossible for us to see directly, since its light would be drowned out by the fierce glare of Betelgeuse.

That sounds good, except there is a problem: the patterns don’t align exactly as a second star would imply. To get past this stumbling block, the authors propose the star is moving clouds of gas and dust around as it orbits, thus explaining the misalignment. But this seems a bit of a stretch, and alone the patterns don’t really prove the star is there.

Another study, however, took a closer look at the wobbles in Betelgeuse’s movements. These have been recorded for over a century, giving plenty of time over which to look for the influence of a second star. And, as before, they found a six year long pattern in this data, constantly maintained over the last century.

Running the numbers, they calculate this implies a star roughly twice the mass of the Sun is orbiting Betelgeuse. More startlingly they think this orbit is unstable, and that eventually - within a few thousand years - the stars will collide, and Betelgeuse will swallow its smaller companion.

But again, their data is not really firm enough to claim a discovery. The wobbles might, they admit, be caused by something else, and direct detection of the star is still impossible with our technology. More studies, and more speculation, will surely be needed.

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James Webb and the Expanding Universe

The debate on the expansion rate of the universe continues to rumble on. Over the past few decades astronomers have tried a variety of methods to measure this rate, and so pin down exactly how fast the cosmos has expanded over time. The trouble is, different methods produce different results, and nobody knows quite why.

Broadly speaking, though, there are two possible explanations. The first is a simple experimental error. The observations needed to calculate the expansion rate are tricky to do, and even though researchers used the Hubble telescope to make them, they may have got things wrong. The second is a flaw in our theories of physics - if something else, something we don’t know about, is driving cosmic expansion, then it might reveal itself in just this manner.

Experimental error is the easier of the two to check. Over the past few years, astronomers have verified the work of Hubble using the new James Webb space telescope. It can see more clearly than Hubble, so it should produce more accurate results and help rule out the biggest sources of error. But, as recent papers have outlined, it has found pretty much the same answer as Hubble. Experimental error, then, seems a bit less likely.

The other option is to rethink our theories of cosmology. But what form that might take is still uncertain. Some argue for new forms of dark energy, or for strange types of dark matter. Maybe new particles are involved, somehow, or perhaps unexpected things happened shortly after the Big Bang. Certainly we are missing something; the only question is what.

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Artemis Delayed… Again

NASA has once again delayed America’s return to the Moon. The next people to set foot on the lunar surface originally hoped to do so in 2024; their mission is now planned for no earlier than 2027. In reality, things are likely to get even worse, at least if NASA insists on sticking to the current plan.

There are now signs of change, however. Donald Trump recently selected Jared Isaacman, a close associate of Elon Musk, to lead the space agency from next year. If confirmed, Isaacman looks likely to rethink NASA’s human spaceflight program, and perhaps to put it on a more realistic path. Certainly, it would be hard to make things worse.

Whether he can really do this, though, remains uncertain. Much of the Artemis moon program is dictated not by NASA, but by the American Congress. And for years Congress has imposed tight budgets and impossible to meet schedules, mandated the use of the expensive SLS rocket, and ignored NASA’s reports on how things could be done better.

Whether that changes in 2025, and whether America can return to the Moon this decade, is thus a political question rather than a technical one. With enough money and freedom to choose the right approach, NASA could certainly put new footprints on the Moon by 2030. Whether America’s politicians are willing to commit to that, however, remains to be seen.