In 2019/2020 I covered, the excitement caused by the apparent and sudden dimming of Betelgeuse, the variable red supergiant in the constellation of Orion, when the star dropped from being the 10th brightest object in the night skies to the 27th before it recovered in early 2020. At the time there was much speculation on whether we were seeing the first signs the star had undergone a supernova explosion some 600 years ago (roughly the time it takes the light from the star to reach us). Obviously, this wasn’t the case, and the “great dimming” as it is now called was eventually pinned on something more mundane.
To put it simply, massive red giants like Betelgeuse are comparatively short-lived, in the order of 10-20 million years, rapidly burning through their stocks of hydrogen, and successively heavier elements in turn. As they do so – and before they reach a point where the fusion process can no longer be sustained as the energy to power it exceeds the amount of energy produced by it, causing the star’s core to collapse under its own gravity in less than a second and then immediately exploding outward again in a supernova – they go through some notable changes. Firstly, as each fusion cycle – helium, carbon, etc. – occurs at higher and higher temperatures, the red giant massively expands into a red supergiant. Secondly, they become violent, throwing off massive amounts of super-heated gas.
Betelgeuse, at around 8.5 million years of age is well into both of these phases; it expended its supply of hydrogen a very long time ago, expanding to its present size of around 600-700 times bigger than the Sun. and it is periodically throwing off vast amounts of super-heated gas into space. With regards to the latter, it is now largely agreed that it was one of these clouds of material which caused the illusion of the “great /dimming”.
Thrown out by Betelgeuse so long ago it had long since cooled to the point it could not be seen from Earth, the cloud gradually drifted in front of our view of Betelgeuse during 2019, giving the impression the star was dimming dramatically. Then, as the dust then moved out of our line-of-sight with Betelgeuse in early 2020, the star appeared to return to its expected luminosity.
As mundane as the explanation for the “great dimming” might be, it nevertheless caused a renewed interest in another of Betelgeuse’s mysteries: does it have a companion star orbiting it? It’s a question astronomers have been trying to answer for almost 100 years; but the very nature of Betelgeuse – its pulsing variability which makes even accurately determining its distance from Earth difficult (it’s thought to be about 640 light-years away, with a margin of error of +/- 146 light years); the huge and glowing masses of super-heated gases surrounding it, etc., – make finding any companion exceptionally difficult.
However, 2024 two separate studies carried were out in the wake of the “great dimming”, examining the gas clouds and the star’s coronasphere to see if there was evidence for either being affected the mass of a stellar object passing through them. Both studies yielded positive results but came to very different conclusions. The first study concluded the companion was either a white dwarf stellar remnant roughly the size of Earth or a neutron star some 10-20 km across. Either way, it likely had a mass roughly equitable to the Sun. However, the second study concluded the companion was almost equitable in size and mass to the Sun, and orbiting Betelgeuse so close it will likely be consumed by the larger star within 10,000 years.
Following up on these studies in 2025, a NASA team observed Betelgeuse using the Gemini North Observatory in Hawai’i. They pretty much confirmed the second of the 2024 studies: there did appear to be a companion star orbiting very close to Betelgeuse; however it appeared to be an F-type pre-main sequence star with roughly 1.5 to 1.6 times the mass of the Sun. Such was the NASA team’s confidence in their findings, they informally named the star: Siwarha, meaning “her bracelet” in Arabic, reflecting the fact that Betelgeuse means “the hand of al-Jawzā”. The name was subsequently accepted by the International Astronomical Union (IAU).
More recently, a team of astronomers used the data from the NASA study to calculate where Siwarha would be at the furthest distance its orbit would carry from Betelgeuse as seen from Earth, and the time at which this would occur. They used these calculations to direct the European Southern Observatory’s Very Large Telescope (VLT) cluster in Chile to observe Betelgeuse at the specified time to try to both image Siwraha and gather more data that might be used to better characterise it.
The results were both satisfying and a little mystifying. On the one hand, Siwraha was exactly where the calculations said it would be, and the team were able to image it. However, the data gathered by the VLT’s instruments suggest Siwarha is a B-type main-sequence star some three times the mass of the Sun and between 2 and six times its size – in other words, very different to the star indicated by the NASA study.
There could be many reasons for this; as noted, trying to identify a stellar body which would effectively be little more than a marble compared to Betelgeuse’s soccer ball, and in so dynamic a region of space, isn’t easy. So as the VLT team note, more observations are required to better understand Siwarha’s nature. But in the meantime, it would seem that the 100-year-old question on whether or not Betelgeuse has a companion has been affirmatively answered.
And what of the potential of Betelgeuse going supernova? Given its age and characteristics, astronomers agree that – if it hasn’t happened in the last 600-ish years – it will happen in the next 100,000. However, if it has happened within the last 600-ish years, our first indication will not be a sudden blossoming of light in the night (or even daytime, it will be that bright) sky. Instead, the first signs of its supernova will come invisibly in the form of a blast of neutrinos hitting a global network of detectors called the SuperNova Early Warning System (SNEWS) located deep underground.
This is because when the core of a star destined to go supernova collapses, it generates a massive burst of neutrinos ahead of the actual supernova event. These travel outward at almost the speed of light, unhampered by the intervening matter of the the star. The light and energy created by the supernova, however, does have to propagate up through those layers of stellar matter, taking several hours to do so. Thus, this neutrino blast will reach us hours ahead of any light from the supernova, and SNEWS will be able to trace their point of origin.
Updates
The Rescuer in need of Rescuing
In June I covered the daring attempt to rescue a NASA satellite – the Neil Gehrels Swift Observatory – from re-entering Earth’s atmosphere in October 2026 and burning up, by using another spacecraft to link up with it and gently push it up to a higher orbital altitude (see: Space Sunday: NASA – a rescue attempt, costs & infrastructure).
The mission got off to a good start. The rescue vehicle, built by Arizona-based Katalyst Space Technologies and called LINK, carried into space by a Pegasus XL air-launched rocket, successfully reached its initial orbit. Once there, it was able to deploy its solar panels for power and enter a period of check-out, calibration and commissioning before starting on its way to rendezvous with the Swift Observatory. However, on July 28th, NASA announced things had gone a little sideways: two out of the three reaction wheels on the spacecraft have ceased functioning, and its cold gas thrusters are also suffering a “loss of functionality”.
Reaction wheels are a means to precisely control the orientation of satellites and spacecraft where the use of thrusters isn’t precise enough and / or could lead to excessive propellant depletion. The failure aboard LINK means it is now slowly spinning and only able to achieve intermittent communications with Earth. Further, the issue with the cold gas thrusters means that these cannot be reliably employed to slow the spin and correct LINK’s orientation.
At the time of writing, both Katalyst and NASA are working through the issues in order to recover the spacecraft. At the same time, and as a back-up measure, work is being carried out to reconfigure the software controlling LINK’s more powerful and propulsive ion thrusters so that if necessary, they might be used in a manner similar the vehicle’s cold gas thrusters, firing short, gentle bursts at appropriate times in the spacecraft’s slow tumble and bring it under control.
And in a twist of history, in 2022, the Swift Observatory also suffered a failure within its reaction wheels, causing NASA to place it in a “safe” mode until the matter was resolved and the observatory could resume normal operations. Hopefully, the same will be true for LINK.
Thar’ She Floats!
It’s probably more than apparent that I’m (one of many) not convinced that SpaceX’s Starship / Super Heavy system is actually a viable commercial launch system with a genuine ROI. It is most certainly not the vehicle that will “take humanity to Mars” or anywhere else in the wider solar system or realistically deliver on any of the other promises made by the SpaceX CEO. However, credit does fall where credit is due.
As I covered in my previous Space Sunday update, the system completed its 13th integrated flight test (IFT-13) on July 24th which achieved the majority of its stated goals, potentially clearing the way for an orbital launch attempt with IFT-14. However, perhaps the most remarkable thing about IFT-13 is the fact that on splashing down in the Indian Ocean, Starship S40 didn’t exit this world by blowing up in the manner of its predecessors, but gently keeled over to float on its back.
And it is still afloat, which is equally remarkable, and speaks to its overall structural integrity. Having taken the time to careful study the vehicle following its splashdown – particularly the condition of its heat shield tiles – SpaceX has indicated it may try to attempt a recovery of the 52-metre long, 100-tonne vehicle by towing to Australia – a distance of around 1,200 km – where it can be transferred to a suitable ocean-going barge for transfer back to the United States!
ESCAPADE’s Long Road to Mars Captures the Moon and Earth
In November 2025, and on its second flight, Blue Origin’s New Glenn rocket sent two small NASA satellites built by Rocket Lab on behalf of NASA on their (indirect) way to Mars (see: Space Sunday: New Glenn “welds” it on second flight!).
The mission, called ESCAPADE (Escape and Plasma Acceleration and Dynamics Explorers) is intended to orbit Mars with the two satellites (informally called Gold and Blue) in a study of the planet’s magnetosphere and how solar wind contributed to the loss of most of the planet’s atmosphere. However, under the original plan, the two 1/2 tonne satellites were supposed to have been launched with NASA’s 16 Psyche mission in 2023, effectively hitching a ride with that spacecraft which would make a fly-by of Mars. However, changes to the 16 Psyche mission meant ESCAPADE could no long launch with it, and so it eventually departed Earth outside of the normal 26-month optimal Earth-Mars launch windows.
This meant that as launched the two satellites could not reach Mars directly. Instead, they were placed on a looping flight around the Sun-Earth L2 position before swinging back towards the Earth-Moon system in first of two fly-bys. This took place in early July 2026, and was used to calibrate the imaging systems on both vehicles, by capturing images of the Earth-Moon system in natural light, ultra violet and infrared.
Both Earth and the Moon are 8% sunlit crescents in the image, with the Sun just out of frame to the observer’s right. The image also presents a comparison of albedo (reflectivity), with Earth is around 30% reflective overall thanks to sunlight being reflected off of the planet’s cloud tops. Meanwhile the Moon is a dull 7%.
When seen in the infrared, the difference is more apparent: even the side of Earth apparently in shadow shines with a temperature range of -43o and -10o, which might sound low in this age of global warming, but remember it is the night side of the planet and includes the temperature of the oceans there. By contrast, the Moon’s shadowed side is -173.3o.
Currently, both satellites are on the outward leg of a shorter loop away from Earth. They will return in November and perform a close gravity-assist flyby which will set them on course to reach orbit around Mars in September 2027.
Inara Pey: Living in a Modemworld 