Study of the giant star Bethel Gemini reveals the cause of its pulses

Study of the giant star Bethel Gemini reveals the cause of its pulses

Recent differences are in the brightness of Betelgeuse. The stellar pulse causes the star’s brightness to vary, but the dramatic drop in brightness in early 2020 was unprecedented. A comparison of live photos of the surface of Betelgeuse between January 2019 and December 2019 shows that large parts of the star faded in December 2019, which may indicate the appearance of a dust cloud in front of it. The images were taken with the Very Large Telescope of the European Southern Observatory (ESO). Credit: ESO / M. Montargès et al

Typically one of the brightest and most distinct stars in the winter sky, Betelgeuse is the left shoulder of the constellation Orion. More recently, however, he’s been acting strange: an unprecedented significant drop in brightness was observed in early 2020, leading to speculation that Betelgeuse may be about to explode.

To find out more, an international team of scientists, including Kenichi Numoto at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), has conducted a rigorous examination of the position of Gemini. They concluded that the star is in the phase of early primary helium combustion (which is more than 100,000 years before the explosion) and has a smaller mass and radius – which is closer to Earth – than was previously thought. They also showed that the smaller differences in the brightness of Betelgeuse were driven by stellar pulses, and suggested that the last large dimming event involved a dust cloud.

The research team is led by Dr Meredith Joyce from the Australian National University (ANU), who was an invited speaker at Kavli IPMU in January 2020 and includes Dr Shing-Chi Leung, a former researcher on the Kavli IPMU project and a current postdoctoral candidate. Researcher at the California Institute of Technology, and Dr. Chiaki Kobayashi, Associate Professor at the University of Hertfordshire, who was an Affiliate Member of Kavli IPMU.

Study of the giant star Bethel Gemini reveals the cause of its pulses

Data holes are periods when Betelgeuse is invisible in the night sky each year. Brightness data were collected by the American Association of Variable Star Observers (AAVSO) observers and the Solar Mass Ejection Imager in space. Data from the latter was processed by László Molnár of the Konkoly Observatory at CSFK in Budapest, Hungary. Credit: L. Molnár, AAVSO, UCSD / SMEI, NASA / STEREO / HI

The team analyzed the variation in the brightness of Betelgeuse using evolutionary, hydrodynamic and seismic modeling. They came to a clearer idea than before that Betelgeuse is currently burning helium in its core. They also showed it Astral pulses Driven by a so-called kappa mechanism, it causes the star to continuously brighten or fade in two periods of 185 (+/- 13.5) days and about 400 days. But the big drop in brightness in early 2020 is unprecedented, and it is likely due to a dust cloud in front of Betelgeuse, as seen in the image.

Their analysis reports that the current mass is between 16.5 and 19 solar masses – which is slightly lower than the most recent estimate. The study also revealed the size of Betelgeuse, as well as its distance from Earth. The actual size of the star was a bit ambiguous: previous studies indicated, for example, that it could be larger than the orbit of Jupiter. However, the team’s results showed that the Orchid is only two-thirds of that, with a radius of 750 times the radius of the Sun. Once you know the physical size of the star, it will be possible to determine its distance from Earth. So far, the team’s results show it is 530 light years away from us, or 25% closer than previously thought.

Their results indicate that Betelgeuse is not at all close to the blast, and that it is so far from Earth that the final blast has a major impact here, although it remains a major problem when the supernova is exploding. And since Betelgeuse is the closest candidate for such an eruption, it gives us a rare opportunity to study what happens stars Like this before it explodes.

Prostrate Gemini is smaller, closer than initially thought

more information:
Meridith Joyce et al, Standing on the Shoulders of Giants: New Estimates of Mass and Distance for the Site of Gemini Through Evolutionary, Chemic, and Hydrodynamic Simulations Composite with MESA, The Astrophysical Journal (2020). DOI: 10.3847 / 1538-4357 / abb8db

Provided by the Kavli Institute for the Physics and Mathematics of the Universe

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