![]() ![]() The Egyptians described the appearance of a “second sun” in the sky, says Webb. There are records from ancient Egypt of what appears to be a star exploding as a supernova. When it does eventually explode, it could – over the course of a week – grow so bright that it will be visible during daylight, and cast shadows at night. Observing its behaviour gives important insights into the behaviour of red supergiants before supernova explosions. “One of the coolest things about Betelgeuse is that we’re watching the final stages of big star evolution play out almost in real time for us, which we’ve never really been able to study in this much depth before,” says Dr Sara Webb, an astrophysicist at Swinburne University of Technology in Australia. As days grow shorter in the northern hemisphere, it will be visible there too.īetelgeuse is expected to explode some time in the next 10,000 to 100,000 years. While the combination of gravity darkening from a tidal bulge raised by a close encounter with a black hole and the ensuing eruption of shrouding material may seem far-fetched, with limited evidence, we can only concoct the best stories possible.In the southern hemisphere sky it can be spotted glowing brightly in the early evening, at the shoulder of the Orion constellation. Further observations, of both Betelgeuse and other red supergiants like it, may reveal an answer. After all, it happened only once in all of our records of the famous star. Combined with the gravity darkening caused by tidal effects, a large amount of ejected material could have briefly obscured our view of Betelgeuse, with the total effect explaining the Great Dimming.Īstronomers may never fully understand what happened to Betelgeuse in late 2019. However, the passage of the visitor may have caused other effects, like a strong stellar outburst. The bizarre dimming of bright star Betelgeuse caused by giant stellar eruption Mystery solved? Dust cloud caused Betelgeuse star's weird dimming, study finds ![]() Mysterious dimming of bright star Betelgeuse may be from 'sunspots' and temperature changes This kind of "gravity darkening" makes some stars appear brighter at their poles than around their middles. That makes the equator of the star sit farther away from the core, which reduces the temperatures and, in turn, the brightness. When they do, the rotational force bulges out their equators relative to their poles. Where that balance point sits determines the star's temperature, and its temperature determines its brightness.Īstronomers can see the effects of this when stars rotate too quickly. So a star's surface is always balanced between these two forces. The stars hold themselves together with the weight of their own gravity, but that force is counterbalanced by the (literally) explosive energies released in their cores. That's because stars aren't solid bodies but rather giant balls of gas. ![]() The brightness of a star's atmosphere depends crucially on how far that outermost layer is from the nuclear core (and any surrounding shells) in the center. One possibility is that the shape of Betelgeuse's outer atmosphere changed, causing a shift in brightness. There's simply too much mass in the core, and the energies released by fusion reactions are simply too high, to support those kinds of quick changes.Īstronomers have proposed many possibilities, including stellar outbursts or giants clumps of orbiting dust. That's because changes to the fusion reactions don't stop and start in only a few months. Whatever caused the dimming also must have come from a situation outside the star itself, rather than being due to some fundamental change in Betelgeuse's internal operations. So whatever caused the "Great Dimming," as it came to be called, must have been truly extraordinary. Just as randomly, the dimming halted in February 2020 and the star began to brighten again, and it has now reached its normal levels of intensity.Īstronomers have records of Betelgeuse going back half a century, and in those records, they could find no precedent for the 2019 event. The dimming continued throughout early 2020, and at its lowest point, the absolute brightness of Betelgeuse dropped by about 60%. So naturally, astronomers were very surprised in late 2019, when Betelgeuse began to dim for no apparent reason. ![]()
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